Lead halide perovskite nanocrystals (LHP NCs) - the latest generation of colloidal quantum dots (QDs) - possess dynamic, entropically stabilized soft lattices and electronically benign surfaces that, remarkably, do not compromise their textbook semiconductor optical quality. They are intrinsically bright emitters without the need for epitaxial wide-bandgap shells. In recent years, LHP NCs have emerged as the most intensively studied QD material, challenging the field's foundational paradigms in nearly every respect. They are the first QDs to exhibit excitonic coherence on timescales comparable to their radiative lifetimes. Their giant oscillator strength effect enables extremely fast emission (lifetimes as short as 60 ps) even in relatively large NCs, while maintaining single-photon emission. Periodic ensembles of LHP NCs have further demonstrated collective, accelerated radiative decay - superfluorescence - a phenomenon previously unseen in colloidal systems. The excitonic fine structure of LHP NCs can be readily engineered through shape anisotropy. Furthermore, by simple near-field coupling to highly chiral plasmonic nanostructures, their otherwise linearly polarized emission becomes fully chiral, establishing LHP NCs as the first fully chiral colloidal single-photon emitters. Beyond photophysics, LHP QDs have recently proven to be efficient photocatalysts, mediating organic redox transformations that remain inaccessible to conventional photocatalysts. The presentation will summarize the contributions of my interdisciplinary team and our international collaborators, whose names will be acknowledged in the presentation and accompanying notes.

Harvesting energy from ambient indoor light poses materials and device challenges that differ fundamentally from those encountered in outdoor photovoltaics. Low illumination intensities, narrow spectral distributions, and long‑term operational stability under constant low‑flux conditions require semiconductors and devices specifically engineered for the indoor regime. In this talk, I discuss recent progress in lead‑free metal halide and perovskite‑inspired semiconductors, with particular emphasis on pnictogen‑based materials, as a promising platform for indoor light harvesting.

Drawing on recent work, I will show how materials engineering, encompassing composition selection, defect chemistry, and structure–property relationships, governs charge generation and transport under low‑intensity indoor illumination. These studies reveal that lead‑free metal halide systems can combine favourable optoelectronic response with improved environmental compatibility compared to lead‑based halide perovskites, while exhibiting distinct recombination and carrier‑localisation phenomena that become critical in the indoor operating regime.

Beyond materials optimisation, the talk addresses device‑ and interface‑level effects on voltage output, reproducibility, and operational reliability at low photon flux. A central message of this talk is that reliable indoor photovoltaics can be achieved through appropriate engineering across materials, devices, and interfaces, highlighting how the indoor photovoltaic regime reshapes the performance–sustainability trade‑off and enables lead‑free perovskite‑inspired materials to become relevant candidates for indoor light harvesting.

Together, these results establish a fundamental framework for designing indoor photovoltaic devices that are both efficient and reliable under realistic conditions. The insights discussed provide a robust scientific foundation for sustainable indoor light harvesting and outline the key challenges that remain in bridging laboratory‑scale devices with practical energy‑autonomous technologies.

Due to the high softness of organic-inorganic halide perovskites, their properties are often studied under high hydrostatic pressure, but the effect of pressure at different temperatures is much less studied. For MAPbI₃ and MAPbBr₃, we observed that the bandgap pressure coefficient is different for different phases, but also varies with temperature [1, 2]. We have also observed a temperature dependence of the pressure coefficient for (4FP)₂SnI₄ [3] and TMA₂SnI₄ [4], but this feature has not been discussed in detail so far, while it is well known that the change of the bandgap pressure coefficient with temperature is unusual for inorganic semiconductors such as Ge, GaAs or GaN and therefore it is interesting to better understand this phenomenon in organic-inorganic halide perovskites. In this paper, we will focus on our recent studies of the bandgap pressure coefficient in ACE₂PbBr₄ at different temperatures, compare these results with calculations performed within the density functional theory, and discuss the reasons for the change in the pressure coefficient with temperature, including the role of the softness of organic-inorganic perovskites and the electron-phonon interaction. So far ACE₂PbBr₄ was studied under hydrostatic pressure [5], but photoluminescence measurements under hydrostatic pressure at various temperatures were not reported for this compound. In this paper we will also present and discuss the pressure dependence of both the near-band edge emission and self-trap exciton emission.

Lead-halide perovskites are attractive optical materials since they combine strong excitonic response, fast emission, and facile solution processing [1]. These features also make them promising scintillators, namely materials that convert high-energy radiation into detectable optical signals for radiation detection, medical imaging, and related photonic technologies. In such systems, both light yield and temporal response are critical, yet they are usually constrained by the intrinsic radiative and non-radiative pathways of the emitting medium. Nanophotonic approaches offer a route to overcome these limitations by modifying how the optical environment interacts with excited states generated under ionizing radiation.

In scintillators, nanophotonic concepts have so far been explored mainly in the weak-coupling regime, where the optical environment modifies the local density of optical states and accelerates radiative recombination through the Purcell effect [2-4]. In this regime, emission can be made faster and brighter, but the emitter and the optical mode remain distinct. A more advanced regime is strong light-matter coupling, in which coherent interaction between excitonic and plasmonic states leads to the formation of hybrid light-matter states with new spectral and dynamical properties [5-7]. Here, we show that perovskite nanoplasmonic scintillators can evolve continuously from Purcell-enhanced emission to strong light-matter coupling.

Our first platform is based on CsPbBr₃ nanocrystals embedded in a transparent PDMS matrix and coupled to plasmonic Ag nanoparticles. These composites behave as Purcell-engineered bulk scintillators, demonstrating that nanoplasmonic rate engineering is not restricted to ultrathin films. In 5 mm-thick composites, we observed up to a 4.2-fold decay-rate enhancement and a 2.1-fold increase in light yield under ²⁴¹Am γ-excitation [3]. This result is important because it shows that plasmonically modified scintillation can be scaled to bulk architectures relevant to practical radiation-detection formats, rather than remaining limited to near-surface or thin-layer configurations.

We then move beyond the weak-coupling regime and demonstrate exciton-plasmon strong coupling in bulk CsPbBr₃ nanoplatelet composites embedded with Ag nanocubes. By tuning nanocube dimensions and temperature, we achieve resonance alignment between excitonic and plasmonic modes and observe Rabi splitting, mode anticrossing, and polaritonic dispersion in angle-resolved photoluminescence. The normalized coupling ratios reach  g/ω_x = ( 0.32 ± 0.01 ) in photoluminescence and ( 0.36 ± 0.01 ) in radioluminescence [5]. These results show that hybrid light-matter states can be formed directly in a bulk scintillating composite under conditions relevant to ionizing-radiation excitation, opening a route toward bulk polaritonic scintillators.

To complement the experiments, we develop a quantum-optical framework for near-infrared nanoplasmonic scintillators [8]. The near-infrared is particularly relevant because lower-band-gap scintillators can, in principle, generate more electron-hole pairs per unit of deposited energy, while conductive platforms such as ITO and graphene can support narrower, lower-loss optical modes than conventional noble-metal antennas [9,10]. Our calculations show that strong-coupling signatures are jointly governed by emitter dephasing and antenna linewidth, with narrow-band emitters and spectrally narrow antennas providing the most favorable conditions. This defines a strategy for scintillators spanning the visible and near-infrared and shows that the concept is not restricted to a single emission window.

Overall, these results establish perovskite nanoplasmonic scintillators as a materials platform in which emission can be engineered across coupling regimes, from rate-enhanced scintillation to polaritonic hybridization. Such behavior may be of future interest for radiation detection, imaging, nuclear batteries, and memory-related radiation-encoding concepts.

Mixed lead-tin perovskites are an important ingredient for all-perovskite tandem solar cells. However, their suitability for large-area applications is yet to be proven. For these applications, stability against oxidation and green processing are key ingredients. We show that films made with green solvents can be as efficient as by conventional processing. In addition, antisolvents that coordinate strongly to DMSO could enhance the long-term stability. Furthermore, we show that processing with annealing techniques compatible with roll-to-roll manufacturing can deliver high-quality films.

Once the films are formed, it is not obvious how lead and tin atoms arrange in the crystal. For example, in a 50:50 mixing ratio, they could arrange in a random fashion, or they could cluster, or order in perfect crystals. We use NMR, EDS, and TEM techniques to show how the atoms arrange. NMR shows that they follow a binomial distribution, and EDS shows no clear cluster formation. With TEM and STEM we directly resolve the atomic-scale ordering.

Halide Perovskites have emerged as a revolutionary class of semiconductors, garnering intensive interest due to their exceptional and tunable optoelectronic properties, including high photoluminescence quantum yield (PLQY), high carrier mobility, and bandgap tunability across the visible spectrum. This versatility is demonstrated across various morphologies, nanocrystals (NCs), powders, thin films, and large single crystals, each offering unique advantages for specific applications. However, the dual challenges of lead toxicity and long-term instability have hindered their widespread adoption. While lead-free tin (Sn) halide perovskites are the most promising alternative, their poor stability, particularly the rapid oxidation of Sn2+ has severely limited the performance and lifetime of all device architectures.

In this presentation, we demonstrate a significant leap forward in stabilizing Sn-based perovskites. We detail how a synergistic approach combining targeted additive engineering and controlled light soaking passivates critical defects, enhancing the material's intrinsic stability. This strategy leads to a remarkable improvement in the operational lifetime of our solar cells, and we dissect the underlying mechanisms that go beyond simply preventing oxidation, enhancing stability and photoconversion performance.

This presentation provides a comprehensive investigation into the controlled synthesis and advanced applications of Sn-Perovskites. We show examples of the synthesis of powder as precursors for thin film formation and for application in LEDs, we will also investigate chiral perovskites. Single crystals have been synthesized by hydrothermal methodology with a without confined space. Overall, this study highlights the structural and compositional engineering required to exploit the full potential of halide perovskites, from nanoscopic to macroscopic forms, as a fundamental material system poised to drive breakthroughs in efficient illumination, coherent light generation, and sustainable chemical synthesis.

Solvent coordination governs phase purity and crystallographic order in quasi-2D Ruddlesden–Popper perovskite thin films

Quasi-2D Ruddlesden–Popper (RP) perovskites have emerged as high-stability alternatives to three-dimensional metal-halide systems, with the bulky organic spacer 2-naphthylammonium (2-NA) offering enhanced resistance to moisture and thermal degradation. [1] However, the steric demand of aromatic spacers introduces significant kinetic complexity during film formation: the competition between spacer intercalation, inorganic framework condensation, and solvent evaporation collectively determines the final phase distribution. Controlling this competition through solvent engineering is therefore the central challenge in producing phase-pure, well-ordered quasi-2D films.

We investigate how solvent coordination strength and volatility modulate the structural organization of films targeting a nominal n = 2 stoichiometry, formulated as (2-NA)₂(MA,FA)Pb₂I₇ using 2-naphthylamine hydrochloride (2-NACl) as the spacer precursor. Four 3:1 (v/v) solvent mixtures were evaluated: A (DMSO:DMF), B (DMF:DMSO), C (NMP:DMF), and D (DMF:NMP). The series was designed to independently vary coordination strength and boiling point: DMF (b.p. 153°C) promotes rapid crystallization, while DMSO (b.p. 189°C) and NMP (b.p. 202°C) stabilize PbI₂ coordination complexes and slow nucleation. NMP was selected specifically for its superior solvation of aromatic species, which may facilitate the self-assembly of the 2-NA spacer layer more effectively than DMSO. [2][3]

X-ray diffraction (XRD) characterization reveals that solvent identity is the decisive factor in both phase purity and long-range crystallographic order. The NMP-dominant formulation (sample C) produced the highest structural quality, with sharp diffraction reflections (FWHM ≈ 0.16°) and well-resolved n = 1 and n = 2 phases — consistent with a slow, thermodynamically guided growth mechanism that allows the 2-NA spacers to adopt a uniform, tilted configuration (~55–65° relative to the inorganic plane).[4] In contrast, the DMF-dominant NMP formulation (sample D) exhibited a kinetically trapped phase landscape comprising n = 1, n = 2, and intermediate species, alongside measurable lattice expansion, suggesting that faster solvent evaporation traps metastable configurations before equilibrium packing can be achieved. The DMSO-based systems (A and B) performed poorly in comparison to their NMP counterparts at equivalent DMF ratios, indicating that NMP's combination of higher boiling point and aromatic solvation capacity provides a qualitatively different growth environment rather than a simple boiling-point effect.

Analysis of the d-spacing data confirms that the 2-NA spacer adopts a consistently tilted geometry in the best-performing films, with tilt-angle uniformity degrading markedly in samples where competitive crystallization kinetics were not adequately suppressed.

These findings establish that while the precursor stoichiometry targets n = 2, the realized phase distribution is primarily determined by the solvent coordination environment during film formation.[5] Ongoing work — encompassing UV–Vis absorption, steady-state and time-resolved photoluminescence (PL, TRPL), photoluminescence excitation (PLE) spectroscopy, and scanning electron microscopy (SEM) — will correlate these structural outcomes with the energy landscape of the resulting phase gradients and charge-transfer dynamics across phase boundaries. Device integration in photovoltaic and light-emitting architectures will follow. The results to date provide a clear design principle: for bulky aromatic spacers in quasi-2D perovskites, maximizing solvent coordination lifetime — through high-boiling, strong Lewis-basic solvents with affinity for aromatic species — is the primary lever for achieving phase-pure, orientationally ordered films.

Non-traditional intrinsic luminescence (NTIL) in non-conjugated systems has opened new directions for light-emitting soft materials, yet its integration into surface-active molecular platforms remains largely unexplored. Here we report amino acid-derived Guerbet-type surfactants as multifunctional materials that combine strong interfacial activity with intrinsic blue emission in the absence of classical luminophores. A series of branched C18 surfactants was synthesised by aldol condensation, catalytic hydrogenation, α-picoline-borane-mediated reductive amination, and deprotection. The resulting surfactants displayed strong surface activity, with sodium salts reducing the surface tension of water to below 30 mN/m and the aspartic acid derivative bC18ASP reaching 25.1 mN/m, outperforming SDS under comparable conditions.

Photophysical analysis revealed pronounced blue luminescence in concentrated solution and in the solid state under UV excitation. Among the investigated compounds, bC18ASP consistently showed the strongest emission across DMSO, methanol, and chloroform. Excitation-emission mapping revealed a broad emissive band in the 380 to 480 nm region with maximum intensity under 340 to 360 nm excitation, while concentration-dependent enhancement supported a cluster-triggered NTIL mechanism driven by through-space electronic interactions and hydrogen-bond-assisted conformational rigidification.

To translate this behaviour into functional light management, related Guerbet-type surfactant films were incorporated into PMMA matrices and evaluated as UV down-converting coatings. Previous film studies established effective UV absorption, visible emission, and reproducible film formation in polymer matrices, with the ortho-aminobenzoic acid-based systems showing the strongest film-level luminescence. Under solar simulation, the best-performing surfactant-containing films delivered a 10 to 12% higher watt output than a blank control film without surfactant, indicating that these materials can actively modify the incident spectral profile in a manner beneficial to solar-energy conversion. Taken together, these results define a new class of intrinsically luminescent, surface-active light-management materials and support their use in UV down-converting films for photovoltaic applications.

Scintillators convert high-energy radiation, such as X-rays and gamma rays, into visible or near-visible photons, underpinning technologies in medical imaging, security screening, and high-energy physics [1]. Their performance is typically defined by light yield, decay time, and radiation hardness, which in conventional materials are largely dictated by bulk crystal chemistry and fixed radiative pathways. Overcoming these intrinsic limitations remains a central challenge in the development of next-generation scintillators.

Perovskite materials have recently emerged as promising candidates in this context, owing to their compositional tunability, solution processability, and exceptional optoelectronic properties [2]. In scintillation, they enable a transition from conventional bulk optimization to quantum-engineered functionality, in which reduced dimensionality, nanoscale structuring, and tailored light-matter interactions provide new handles to control energy conversion processes [3-6]. This shift opens opportunities to redefine performance limits beyond those accessible in traditional scintillators.

Low-dimensional perovskites, including PEA₂PbBr₄, BA₂PbBr₄, CsCu₂I₃, and Cs₃Cu₂I₅, exhibit strong quantum confinement and enhanced excitonic effects, resulting in high light yields between 10 ph/keV and 60 ph/keV with fast scintillation lifetimes between 3 and 1000 ns at room temperature (RT) [3-5]. Their tunable emission and large exciton binding energies contribute to improved scintillation performance relative to bulk systems. Structural engineering strategies, such as ligand modification [7], ion doping [8,9], and anion substitution [10], enable precise control over band structure and defect landscapes, allowing simultaneous optimization of spectral and temporal response. At the nanoscale, quantum dots and related architectures introduce further control via size-dependent electronic structure and multiexciton dynamics, enabling enhanced light yield, ultrafast emission, and improved radiation stability compared to bulk counterparts [5,6]. For example, large improvements in light yield were achieved in quantum dots, with the RT light yield reaching approximately 30 ph/keV, compared to less than 0.1 ph/keV in bulks [6].

Beyond materials design, engineered light-matter coupling provides an additional route to control scintillation. Nanophotonic and plasmonic structures can modify the local density of optical states, enabling Purcell-enhanced emission and cavity quantum electrodynamics effects [11,12], while energy-transfer processes such as Förster resonance energy transfer further improve emission efficiency and timing characteristics [9]. Together, these advances establish perovskite scintillators as a platform that integrates quantum materials design with photonic engineering, offering new opportunities for high-performance radiation detection and emerging applications in imaging and sensing.

Perovskite thin films exhibit exceptionally high material gain under optical excitation, enabling low threshold amplified spontaneous emission and lasing across a wide spectral range. Translating these gain properties into electrically pumped laser operation, however, remains a major unsolved challenge. Unlike optically pumped devices, electrically driven perovskite gain media must simultaneously satisfy requirements on charge injection balance, carrier density, thermal management, and optical feedback, all within a materials system characterized by mixed ionic–electronic transport.

In this presentation, we focus on the electrical generation of optical gain in perovskite thin films and assess the physical bottlenecks that currently limit electrically pumped operation. We begin with an overview of recent progress in electrically driven perovskite emitters approaching the gain regime.

A central theme of the talk is a direct, quantitative comparison between optical and electrical pumping under matched excitation conditions. By using identical pulse lengths, repetition rates, and duty cycles, we isolate intrinsic gain dynamics from extrinsic electrical effects. This side‑by‑side comparison reveals pronounced differences in gain efficiency and temporal stability, with Joule heating emerging as the dominant limitation for electrically injected carriers. Even for short electrical pulses, resistive losses substantially reduce the achievable carrier density and induce spectral shifts that are absent under purely optical excitation. These experiments provide clear insight into how thermal effects, rather than fundamental gain limitations, constrain electrically pumped perovskite lasers.

To further disentangle electrical injection from optical gain generation, we elaborate on the co‑pumping approach in which electrical and optical excitation pulses are temporally overlaid. In this hybrid configuration, the optical pump serves as a well‑defined gain reference, while the additional electrical injection modifies the carrier population and modal gain. By monitoring changes in amplified spontaneous emission intensity, threshold behavior, and spectral linewidth, the electrical contribution to the total gain can be quantified directly. This methodology enables a systematic analysis of gain enhancement and establishes co‑pumping as a powerful diagnostic for evaluating electrically driven gain in perovskite thin films.

In the final part of the presentation, we report on our recent progress in resonator design for perovskite‑based lasers, with a focus on concepts compatible with electrical injection and reproducible fabrication. We discuss resonator architectures that provide robust optical feedback while minimizing additional losses and thermal load, as well as integration strategies with planar photonic platforms. These efforts aim to establish scalable and reliable cavity concepts that bridge the gap between optically pumped demonstrations and electrically driven perovskite laser diodes.

Together, these results provide new physical insight into electrically generated gain in perovskite thin films and outline clear pathways toward integrating perovskite gain media with practical optical resonators for future thin‑film laser diodes.

Nucleation and growth kinetics within the supersaturation regime fundamentally dictate crystalline architecture and defect evolution. By operating precisely within the thermodynamic metastable zone width (MSZW), crystal growth can be selectively partitioned: the lower boundary near the equilibrium solubility curve favors the slow, thermodynamic stabilization of high-density facets via Bravais’ law, whereas the upper boundary near the labile limit shifts kinetics toward the Frank–Chernov regime, where morphology is driven by fast-propagating, low-(d)-spacing planes. Here, we exploit these localized intra-metastable zone dynamics to demonstrate the controlled synthesis of hierarchical, multiscale perovskite superlattices within bulk halide perovskite crystals. Utilizing either single-stage or two-stage kinetic pathways designed to systematically sweep across the metastable zone, we realize three-dimensional crystalline assemblies composed of overlapping atomic planes with diverse interplanar spacing. Partial commensuration between these kinetically trapped lattice planes gives rise to an array of quasiperiodic configurations that maintain long-range translational symmetry. Within these metastable-engineered bulk perovskite superlattices, we observe robust excitonic collective phenomena, including superradiant emission with thermal stability persisting to elevated temperatures. These results decisively expand the scope of moiré engineering into bulk solids, establishing versatile operational platforms for next-generation quantum photonic applications under ambient conditions.

Metal halide perovskites have emerged as promising materials for next-generation quantum photonic and coherent light-emission applications due to their exceptional optoelectronic properties, high photoluminescence quantum yields, long carrier diffusion lengths and strong excitonic behaviour. However, conventional nanocrystal superlattices frequently suffer from ligand-induced decoherence, interparticle grain boundaries, and structural disorder, limiting the preservation of long-range optical coherence required for cooperative emission phenomena such as superradiance. Continuous single-crystal superlattice architectures may provide an alternative route towards structurally coherent room-temperature quantum emitters.

In this work, we investigate the additive-assisted inverse temperature crystallisation (ITC) growth of mixed-cation methylammonium-formamidinium lead iodide (MAFA) single crystals and superlattice-like architectures. The crystallisation process is systematically engineered using hydroiodic acid (HI), acetic acid (AcOH) etc., as chemical additives to modulate precursor coordination chemistry, supersaturation kinetics, nucleation behaviour, crystal growth dynamics, suppress rapid nucleation and favour the formation of large, homogeneous, and structurally ordered single crystals.

The additives are expected to influence the Pb-halide coordination equilibria and prolong the metastable crystallisation window during growth in γ-butyrolactone (GBL), enabling improved control over crystal morphology, facet development, and long-range structural ordering. In particular, HI is investigated for its ability to enhance iodide coordination and precursor solubility and AcOH for modulation of crystallisation kinetics through weak protonic coordination effects.

The resulting MAFA single crystals and superlattice-like structures are characterised using X-ray diffraction (XRD), optical microscopy, and micro-photoluminescence (μ-PL) mapping in order to evaluate phase purity, crystallographic ordering, morphology evolution, and spatial optical homogeneity. The relationship between additive chemistry, crystal growth pathways, and the emergence of ordered superlattice features is explored as a route towards coherence-preserving halide perovskite architectures.


 

Navigating the vast, high-dimensional chemical space of colloidal nanocrystals remains a formidable challenge, as non-additive compositional and surface interactions render one-variable-at-a-time experimentation fundamentally insufficient for rational design with targeted optical properties. Autonomous, closed-loop synthesis platforms have emerged as powerful tools to address this, yet existing approaches are limited by optimizing crude reaction mixtures whose optical properties bear little resemblance to purified, processed material.

Here we present a closed-loop robotic platform based on our house-built Robowski ^[1,2], uniquely integrating automated synthesis, purification, post-synthetic passivation, and photophysical characterization within a single workflow, producing fully processed nanocrystals at a throughput exceeding 200 formulations per day. We apply this platform to the targeted discovery of highly photoluminescent deep blue-emitting mixed CsPbBr_3-xCl_x nanocrystals (λ_em < 465 nm), the most demanding color band for perovskite light-emitting diodes.

Robowski synthesizes monodisperse spheroidal CsPbBr₃ NCs via ligand-assisted nucleation at room temperature ^[3], followed by metal chloride exchange to blue-shift emission toward the target range. Twelve metal chlorides are systematically screened, seeding a closed-loop Bayesian optimization campaign, in which each cycle the platform synthesizes suggested compositions, acquires their photophysical data, and feeds the results back to the model to guide the next batch.

Navigating through a theoretical space of ~100,000 multi-metal co-dopant compositions, just 278 experiments across four iterative cycles successfully uncover a Zn-dominant domain as the most photoluminescent region. Subsequent exploration across ten post-synthetic passivation agents spanning inorganic cations, small organic ammoniums, and long-chain ammonium salts reveals that a synergistic combination of primary and quaternary long-chain ammonium salts achieves surface reconstruction inaccessible to either agent alone.

Manual validation of the champion formulation yields a near-unity photoluminescence quantum yield of 94.7% at λ_em = 458 nm even after three washing cycles, compared with 14.9% for untreated sample. Ranking among the highest reported PLQYs for deep blue-emitting perovskite nanocrystals, this work demonstrates the potential of accelerated, closed-loop robotic platforms as a powerful and enabling strategy for the targeted discovery of high-performance functional nanomaterials.

Chiral metal halide perovskite nanocrystals (NCs) are becoming prominent as promising materials for chiroptical applications, yet the relationship between chiral ligands surface modification and optical properties remains poorly understood in scalable solution-processed systems. In this work we report the synthesis of chiral formamidinium lead bromide (FAPbBr3) NCs via ligand-assisted reprecipitation (LARP). For that we have introduced enantiopure (R)- or (S)-2-Octylamine in a symmetric series of dilution at 20, 40, and 60 mol % and compared with non-Chiral n-Octylamine. X-ray diffraction confirms that the pure cubic structure is retained in all samples, demonstrating that chirality does not induce bulk lattice distortion. UV-Vis absorption shows an enhanced excitonic confinement in chiral NC samples relative to the non-chiral control, while time-resolved photoluminescence shows a systematically longer exciton lifetimes after the incorporation of the chiral ligands. Circular dichroism (CD) spectroscopy confirms that the maximum in the CD spectra correlating precisely with the NC excitonic absorption between ~ 430-450 nm. The enantiomers yield mirror-image CD spectra, while a racemic (R+S) mixture produces a flat baseline, confirming the molecular origin of the chiroptical response. It is noteworthy that the intensity of the CD signal increases inversely with the concentration of the chiral ligand, with the addition of 20 mol % producing the strongest response. This work demonstrates the LARP method as a scalable and accessible technique to synthesize chiral perovskite NC emitters and provides quantitative design guidelines for optimising chirality through surface ligand engineering.

Hybrid organic-inorganic lead halide perovskites have emerged as promising materials for solar cells, garnering significant research interest over the past decade. An important factor for fabricating efficient and stable perovskite solar cells (PSCs) is the suitability of passivating interlayers and charge extraction layers. However, their introduction to either of the perovskite interfaces can lead to unwanted recombination pathways or more complicated recombination dynamics. For example, the deposition of C60, commonly employed as an electron transport layer for p-i-n PSCs, introduces deep trap states and additional recombination-induced loss pathways [1]. As such, it is crucial to identify the effect of each layer of a complete PSC (charge transport layer, interlayer, absorber) in terms of loss contribution, and to build a robust methodology for correlating results across different characterisation techniques.

Herein, we present a joint analysis framework that simultaneously correlates transient photoluminescence (TRPL) and nanosecond transient absorption spectroscopy (nsTAS) in perovskite thin films and half-stacks with solar cell-relevant architecture. We identify among competing recombination pathways following photoexcitation, with the development of appropriate physical models ^[2,3]. We then employ a Markov-Chain Monte-Carlo (MCMC) model to jointly explore the full TRPL and nsTAS parameter space, quantifying each recombination process described within the model. We apply this methodology to elucidate the effect of various interlayers on recombination dynamics, differentiating between chemical and field-effect passivation mechanisms, thus identifying the limitations of materials commonly employed in device design. This constitutes a robust protocol for systematically guiding future material and device development ^[4].

Metal halide perovskite solar cells have become a viable option for future renewable energy. Record single and tandem junction all-perovskite solar cells already provide power efficiencies of over ~27% and ~30%, respectively. The next target in photovoltaic energy conversion can possibly be met by developing all-perovskite multi-junction solar cells. These require highly efficient and stable perovskite sub-cells with bandgaps in wide spectral range. Especially for narrow and wide bandgap perovskites several challenges remain in reducing the energy loss between bandgap and open-circuit voltage and in stability. By monolithically stacking multiple perovskite sub cells with complementary bandgap using recombination junctions designed to provide near-zero electrical and optical losses, it is possible to fabricate monolithic multi-junction configurations with high power conversion efficiencies. Within this general framework I will focus on recent results.

For narrow bandgap (1.25 eV) tin-lead perovskites we developed a novel insulating-passivating interfaces for the electron and hole transport layers that enable high-photovoltage in single- and double-junction solar cells.

To create an optimal bandgap (1.34 eV) absorber for single-junction solar cells we  established a novel mixed-metal mixed-halide perovskite composition. The optimized perovskite did not show signs of light-induced halide segregation during prolonged illumination. Optimizing the device configuration resulted in a power conversion efficiency of 19% [1], among the highest for perovskites in the 1.3 − 1.4 eV bandgap range.

For very wide-bandgap (2.3 eV) perovskite solar cells a dual-passivation strategy has been found for bulk and surface passivation, which, combined with a ternary fullerene blend electron transport layer, increase the open-circuit to 1.60 V. Integrated into a coupled photovoltaic-electrochemical  system for continuous solar-driven water splitting we achieve unassisted solar-to-hydrogen conversion efficiency of 6.5% [2], outperforming single-absorber reported to date.

Next to device performance, we studied the shallow defect properties in metal-halide perovskite films by measuring transient photoluminescence. Interestingly, lowering the temperature changes the trap energy landscape, making the shallow defects shallower until they vanish into the conduction or valance bands at cryogenic temperature. This result is corroborated by an increase in PL quantum yield and is explained by noting that the shallow defects are intrinsic to the perovskite and formed in a thermally activated process.  The results provide a new insight into perovskite shallow defects and recombination losses and can help us to better understand the effect of surface treatments on shallow defect properties.

Halide perovskites are often discussed in terms of their remarkable optoelectronic performance, but their most distinctive feature may be their chemically and ionically dynamic nature. Unlike conventional semiconductors, these materials possess soft lattices, low formation energies, mobile ionic species, and strong coupling to electrical and environmental stimuli. These characteristics are frequently associated with instability, hysteresis, and device-to-device variability. Yet the same phenomena can also be exploited to create new functionality when understood and controlled.

In this talk focuses on how chemical dynamics can be turned from a limitation into a design parameter across halide perovskite technologies. First, in tin-based perovskites, sulfur-containing molecular additives can regulate precursor coordination and crystallization, suppress Sn(II) oxidation, and reshape degradation pathways. Under realistic stress conditions, these materials reveal reversible transformations and even spontaneous performance recovery, showing that degradation in soft semiconductors is not always a one-way process. Second, I will show how ionic redistribution and electrochemical processes can be harnessed in perovskite memristors, where resistive switching emerges from the same dynamic material response that complicates photovoltaic operation. This provides a direct link between defect chemistry, ion migration, and computing-oriented device functionality.

Because these materials evolve during operation, understanding them requires characterization tools that move beyond static snapshots. I will discuss operando approaches that combine impedance spectroscopy with luminescence analysis to separate fast electronic processes from slower ionic and interfacial dynamics, quantify non-radiative losses, and identify the onset of reversible and irreversible degradation. Together, these results illustrate how embracing chemical dynamics can guide the development of more robust perovskite devices for energy conversion and information processing, while offering broader insight into hybrid semiconductors whose functionality is inseparable from their evolving chemical state.

Halide perovskites underpin two converging frontiers in optoelectronics: scalable photovoltaics and neuromorphic computing. Yet the same coupled ionic–electronic transport that makes them versatile also drives the degradation and metastable phenomena that limit operational lifetimes. Because halide migration, phase segregation and ion redistribution emerge only under realistic biasing, illumination and thermal cycling, ex situ tools alone cannot capture them. Our group addresses this gap with an operando workflow that combines in-house transient and steady-state electrical setups,  light, bias and temperature resolved  with dedicated post-mortem characterisation, closing the loop between device behaviour and material evolution.

I will discuss two complementary case studies. At high TRL, outdoor ISOS-O monitoring of large-area perovskite modules at the HMU Solar Farm, the world’s first perovskite outdoor testbed [1] — reveals how combined illumination, temperature, humidity and bias drive long-term degradation, including partial dark-storage recovery and the emergence of visual defects [2]. This methodology underpins our upscaling pipeline from 156 cm² modules to 0.73 m² panels [3] and the recent demonstration of MXene-driven nanoscale field-effect junctions for 4-terminal perovskite/silicon tandem modules [4]. At low TRL, we link internal ion dynamics to resistive switching in Pb-free perovskite optoelectronic memristors: electrode engineering of AgBiI₄ devices enables a deterministic transition between volatile and non-volatile regimes, supporting dual-mode multifunctional neuromorphic operation [5], while inorganic Cs–Bi–I memristors exhibit threshold switching suitable for energy-efficient neuron emulation [6].

Taken together, these results illustrate how an operando-by-design approach, anchored in the mechanistic understanding of ion–defect interactions, accelerates the rational engineering of perovskite optoelectronics for outdoor energy harvesting and edge-side neuromorphic computing.

Multilayered Ruddlesden–Popper (RP) perovskites represent a promising platform for the development of multifunctional optoelectronic materials. Their unique layered architecture enables independent tuning of structural, optical and electronic properties through the choice of organic cations and the control of their dimensionality. [1-2]

In this presentation we uncover new two-dimensional hybrid RP crystals characterised with short intralayer distance due to incorporation of new spacer cations. Thanks to unique structural characteristics and dynamics of both spacer and cage cation analysed crystals present switchable dielectric properties, persistent disorder and narrowband emission. By using multi-technique approach we were able to describe the origin of mentioned properties and propose specific emission mechanism. The optical analysis of crystals showed anomalies such as rising in intensity up to 100K and relatively steady emission. Such behaviour, when compared to classical perovskite crystals, exclude the possibility of standard decryption of bands as arising from free and bound exciton recombination and thus origin of the emission was proposed to be related to local exciton (LE) recombination. Our proposal is further supported by subsequent analysis of band gap evolution as function of temperature, which revealed that the studied crystals exhibited band gap widening up to 120K followed by band gap narrowing, which corelates with report of J. Deveikis et. al. for ThMA₂PbI₄.[3] Our results highlight the critical role of structural dynamics and disorder in governing excitonic processes in two-dimensional perovskites and provide new insights into possible emission mechanisms of these structures.

Organic–inorganic hybrid perovskites, particularly methylammonium lead iodide (CH₃NH₃PbI₃, MAPbI₃), are promising photoactive materials for photovoltaic applications due to their excellent light-harvesting capability, long carrier diffusion length, and solution-processable fabrication. However, pinhole formation, uncontrolled crystallization, and defect-rich grain boundaries continue to limit the reproducibility, efficiency, and stability of perovskite solar cells. Controlling crystallisation dynamics with suitable additives and anti-solvent treatment is therefore essential for obtaining compact, defect-minimised films.

In this study, a novel 2,4-diamino-6-phenyl-1,3,5-triazine-linked naphthalene diimide compound (t-NDI) was synthesized and used as an additive in the MAPbI₃ precursor system. Combined with a precisely timed toluene antisolvent washing step, this approach regulated nucleation and crystal growth under ambient conditions, eliminating the need for an inert argon atmosphere. X-ray diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence (PL) analyses confirmed improved crystallinity, enlarged crystal domains, and reduced defect density. Additive-free devices exhibited a short-circuit current density (Jsc) of 24.5 mA cm⁻², an open-circuit voltage (Voc) of 1.025 V, a fill factor (FF) of 0.62, and a power conversion efficiency (PCE) of 15.5%. In contrast, t-NDI-containing devices showed a Jsc of 23.1 mA cm⁻², a Voc of 1.036 V, an improved FF of 0.69, and a higher PCE of 16.5%. The performance enhancement was mainly attributed to the improved fill factor upon incorporation of the t-NDI additive. These findings demonstrate a simple, scalable, and experimentally accessible strategy for fabricating high-quality MAPbI₃ films for efficient perovskite solar cells under ambient conditions.

Metal halide perovskites (MHPs) are mixed ionic-electronic semiconductors with outstanding optoelectronic properties.¹ Their low-temperature solution processability, high radiative efficiency, tunable bandgaps, and defect tolerance make them attractive for applications ranging from light emission and lasing to sensing and memory devices². However, their integration into practical device platforms requires robust strategies for controlled patterning and integration with functional contacts and device architectures.³ The development of patterning methods for MHPs remains challenging due to their intrinsic ionic nature and their sensitivity to the solvents used in standard lithography processes.

I will present our recent progress in developing a versatile top-down patterning method based on photolithography and reactive ion etching (RIE), which can be tuned to accommodate different perovskite compositions and morphologies.⁴ This process preserves the functional properties of the perovskite while enabling device-level integration and reproducible fabrication of micron-sized features down to 1 μm across different chips. I will discuss the implementation of these patterned MHPs in photonic devices, including lasing, as well as in perovskite-based memory devices with potential for neuromorphic computing.

For laser devices, a cesium lead bromide (CsPbBr₃) perovskite laser was monolithically integrated on a silicon nitride waveguide platform with a first-order grating distributed-feedback (DFB) cavity. The device operated at 540 nm in the green spectral region, where III-V lasers have limitations, and exhibited a threshold of 0.755 mJ cm⁻². For memory devices, patterned CsPbBr₃ layers were integrated into vertical nickel (Ni)/CsPbBr₃/aluminum (Al) memristors with a 50 μm × 50 μm active area, showing forming-free bipolar resistive switching, high ON/OFF ratios of approximately ~10⁶–10⁷, state retention of > 2×10⁵ s, and stable operation over extended ambient storage.

Overall, this talk will highlight how perovskite structuring can serve as an enabling strategy for different classes of devices at the interface of lighting and computing.

Hybrid halide perovskites are opening new directions for neuromorphic and adaptive electronics because their electrical response naturally combines electronic transport, ionic motion, trapping, and interfacial polarization. Rather than viewing these processes only as sources of instability, an emerging perspective is to treat them as functional ingredients for memory, plasticity, and reconfigurable device operation.

Our recent work explores this idea across a broad family of perovskite systems, including polycrystalline and single-crystal materials [1, 2], lead-based and lead-free compounds, and electrically and optically driven device architectures. Across these platforms, a common physical picture is emerging: the interplay of traps, mobile ions, and metal/perovskite interfaces governs the evolution of conductance over multiple timescales, from fast response to slow relaxation and memory. This framework makes it possible to connect phototransport, hysteresis, threshold switching, persistent response, and synaptic-like dynamics within a unified view of perovskites as dynamically active semiconductors.

A central result of these studies is that, beyond peak performance, repeatability is a key metric for neuromorphic hardware. In our perovskite devices, repeatable conductance evolution is observed together with well-defined hysteretic behavior, threshold-activated responses, and controllable short-term memory. In particular, pulse-driven experiments reveal synaptic functionalities such as potentiation/depression, learning-forgetting-relearning behavour and tunable retention. These effects are consistently linked to the coupled action of trap states, mobile ions, and contact-induced interfacial barriers, which govern how conductance evolves under electrical or optical stimulation.

By combining material synthesis, structural and optical characterization, and device-level transport studies, hybrid perovskites emerge not only as high-performance optoelectronic materials, but also as a rich platform for light-tunable memories and neuromorphic optoelectronics.

The commercial implementation of lead halide perovskite in optoelectronic applications, particularly in X-ray imaging and radiation detection, has been significantly hindered by their toxicity, instability, and strong self-absorption [1,2]. In this study, we explore lead-free copper iodide perovskite as environmentally friendly, earth-abundant, and cost-effective alternative materials for scintillator-based radiation detection. Among all the phases of cesium copper iodide compound, CsCu₂I₃ (1-D structure) and Cs₃Cu₂I₅ (0-D structure) are the two stable phases that exhibit broadband yellow and blue emission, respectively [3]. These materials possess promising optoelectronic properties, including high stability and bright emission, which are essential for scintillator. Their large Stokes shift enables low reabsorption losses, which is critical for achieving high scintillation efficiency [2,4].

In this study, we present a comparative study of CsCu₂I₃ and Cs₃Cu₂I₅ nanocrystals (NCs) synthesized via a mechanochemical ball milling method. These NCs are expected to enhance the scintillation performance properties compared to those observed in previous studies. This approach offers a simple, cost-effective, and scalable method that is suitable for large-scale production. Previous studies have reported that the light yield of CsCu₂I₃ and Cs₃Cu₂I₅ NCs synthesised via mechanochemical using mortar is 12.54 ph/keV and 16.5 ph/keV, respectively, with decay time of 125 ns and 841 ns [1]. Furthermore, CsCu₂I₃ nanocrystals (NCs) embedded in polymer resin using the same fabrication approach exhibit a light yield of 9.4 ph/keV at 180 K and approximately 2 ph/keV at room temperature [2]. However, this reduced light yield is primarily attributed to Fresnel losses introduced by the polymer matrix [2]. In comparison, CsCu₂I₃ single crystals synthesized via the antisolvent vapor crystallization method show significantly better performance, delivering a light yield of 26.5 ph/keV, an average decay time of 93 ns, and an energy resolution of 8.5%, indicating that single crystals still provide superior light yield, albeit with slower response times. Interestingly, depositing NCs on the surface of these single crystals leads to lower light yield but faster decay times, including a notable sub-nanosecond component [5]. Further optimization of the scintillation properties of such hybrid NC–crystal systems will be explored in future work.

From the NC perspectives, these results highlight the strong potential of copper iodide perovskite NCs for use in scintillator-based radiation detection systems and provide a benchmark for evaluating the performance of the mechanochemically method with further optimization.

Self-powered photodetectors and indoor photovoltaics have attracted significant attention for renewable energy generation, sensing, and advanced optoelectronic systems. Despite their exceptional optoelectronic performance, the high toxicity of lead and long-term ambient instability necessitate the development of alternatives to lead-halide perovskites (LHPs). Bismuth and antimony-based halide perovskite-inspired materials (PIMs) have attracted significant attention as environmentally friendly and stable replacements to LHPs. However, the optoelectronic performances of PIMs are still poor compared to LHPs, mainly due to their wider bandgap, reduced electronic dimensionality, larger carrier effective mass, strong self-trapped exciton formation, and low mobility-lifetime product. In this study, we have synthesized an electronically 2D PIM, Cs₂AgBi₂I₉ (CABI), via partial incorporation of Ag⁺ at the A-site of the highly stable Cs₃Bi₂I₉ (CBI) lattice. The partial incorporation of Ag⁺ results in a narrower band gap of 1.78 eV, attributed to the orbital hybridization between Ag 5s and I 6p orbitals. A larger polaronic radius (34 Å) of CABI is estimated via density functional theory in comparison with CBI (21 Å). Consequently, the 2D-CABI demonstrated outstanding carrier mobility-lifetime product (μτ) of 3.4 × 10⁻³ cm²V⁻¹, weaker electron-phonon coupling, and longer hot-carrier lifetimes compared to other solution-processed Bi-PIMs.[1] With those exceptional properties, CABI-based self-powered photodetector and indoor photovoltaic devices have been developed, delivering the highest responsivity of 0.219 mA/W under 19 μW/cm² illumination and PCE of ≈8% under 1000 lux illumination, which are the highest among other PIMs [2]. Owing to the narrowed bandgap, the devices deliver broadband photodetection performance and operate effectively under diverse indoor lighting environments with color temperatures ranging from 2700 to 6500 K. This work opens a new avenue for exploring the potential of double A-site cation-based PIMs for designing next-generation optoelectronic technologies

The performance and operational stability of lead halide perovskite optoelectronics are persistently limited by surface defects arising from residual precursor phases, undercoordinated lead, and halide vacancies. Here we show that a single multifunctional organic salt, 2-diethylaminoethanethiol hydrochloride (DEAET), bearing a thiol and a protonated tertiary amine, can address these challenges across three distinct perovskite device technologies, adapting its interaction pathway to the stoichiometric environment of each underlying film. In PbI₂-rich FAPbI₃ solar cells, DEAET reduces residual PbI₂ by ~40% and fully eliminates metallic Pb⁰ through thiol and ammonium coordination, without forming low-dimensional phases, delivering an average PCE of 19.0% (champion 21.0%) and stable operation exceeding 350 h. In FAI-rich FAPbI₃ LEDs, the molecule instead regulates residual formamidinium iodide through hydrogen bonding and electrostatic interactions, raising the PLQY from 9% to 30% and yielding devices with ~14% EQE and 15-day air stability without encapsulation. In mixed-cation CsFAMA memristors, DEAET reacts with excess PbI₂ to form a low-dimensional perovskitoid overlayer that confines the conducting filament, achieving 100% device yield, over two months of stable operation, and 400 fJ per synaptic event under light illumination. This work demonstrates, for the first time, that a single molecular additive can unify the passivation of solar cells, LEDs, and memristors, establishing a new paradigm for the rational molecular engineering of perovskite optoelectronics.

Metal halide perovskites have emerged as star materials for next-generation photovoltaic technology due to their outstanding optoelectronic properties, with laboratory device efficiencies exceeding 27%. However, their intrinsic stability remains a core challenge for industrialization. Research indicates that different crystal facets in perovskite polycrystalline films exhibit significantly varying environmental stability—the (111) facet demonstrates excellent moisture resistance, while the (100) facet is prone to water and oxygen erosion, serving as a weak point for phase transitions and degradation. Therefore, achieving precise control over crystal orientation, suppressing unstable facets, and promoting the preferential growth of stable facets is a key pathway to simultaneously enhance device efficiency and stability.

This talk systematically presents our team’s synergistic strategies for controlling perovskite crystal orientation. First, in inverted structures, the introduction of NaCl into the PEDOT:PSS hole transport layer induced preferential orientation of perovskites along the (100) direction, revealing the role of lattice matching in heterogeneous nucleation. Subsequently, for conventional structures, the multifunctional molecule biguanide hydrochloride (BGCl) was introduced at the SnO₂/perovskite interface. Through Lewis coordination and electrostatic coupling, this optimized interfacial energy level alignment, passivated defects, and promoted high-quality perovskite crystallization, achieving a high efficiency of 24.4% and excellent environmental stability. Furthermore, we utilized the natural compound tea saponin (TS) to modify the SnO₂ surface. Through synergistic hydrogen bonding and Lewis coordination, this successfully guided the dominant growth of the perovskite (111) facet, resulting in a photoelectric conversion efficiency of 24.2% and significantly enhanced humidity tolerance.

To fundamentally address the instability of the (100) facet, we innovatively designed a functional additive containing triformyl (TFPA). Combined with advanced characterization techniques such as in-situ GIWAXS, terahertz spectroscopy, and scanning electron diffraction navigation imaging, we confirmed that TFPA selectively anchors to the (100) facet, suppressing its growth while guiding preferential orientation toward the (111) facet. This strategy not only significantly increased the energy barrier for the α-to-δ phase transition, enhancing intrinsic stability, but also optimized charge transport properties, ultimately achieving a balance between high efficiency and long-term stability.

In summary, through a synergistic three-pronged strategy of “interface engineering—molecular design—facet regulation”, this work achieves precise control over perovskite crystal orientation. It provides a universal technical pathway for developing perovskite solar cells with both high efficiency and high stability, strongly advancing their practical application.

The future of visual interfaces is evolving into immersive, form-factor-free, and hyper-realistic experiences that transcend traditional screen boundaries. This presentation highlights breakthroughs in advancing next-generation optoelectronics through the strategic design of functional materials for high-performance optoelectronics, and next-generation wearable intelligence.

First, we address the critical challenge of stability and efficiency in colloidal perovskite nanocrystals (PeNCs). We introduce a rationally designed hierarchical shell (HS) architecture consisting of interbonded PbSO₄-SiO₂-polymer layers.^[1] This lattice-interface interlocking mechanism effectively restricts lattice expansion and passivates reactive surfaces, achieving near-unity photoluminescence quantum yield (PLQY).^[1] This architecture delivers an unprecedented external quantum yield of 91.4%, and snrues commercially viable operational stability, such as T₉₀ > 3,000 hours at 60°C/90% RH and T₉₀ > 20,000 hours under blue light, while fundamentally preventing lead leakage.^[1]

Furthermore, we overcome industrial scalability hurdles through a pseudo-emulsion-based cold-injection synthesis.^[2] By leveraging cold temperatures (< 4 °C) to control the assembly of polybromide plumbates, we suppress defect formation and enable massive production up to a 20-liter scale while maintaining high PLQY.^[2] The resulting PeNCs have been successfully integrated into high-efficiency perovskite light-emitting diodes (PeLEDs) achieving an external quantum efficiency (EQE) of 29.6%, nearing the theoretical maximum.^[2]

Moving beyond static performance, we extend these capabilities into deformable electronics. We present fully stretchable organic light-emitting diodes (OLEDs).^[3] By integrating MXene-contact stretchable electrodes (MCSEs) with an intrinsically stretchable exciplex-assisted phosphorescent layer, we achieved a record-high EQE of 17.0% in fully stretchable configurations.^[3] These devices demonstrate negligible luminescence degradation even under 60% strain, providing a foundation for future on-skin displays.^[3]

Defects and grain boundaries remain critical bottlenecks in unlocking the full potential of perovskite semiconductors in applications. In this talk, I will present a scalable strategy to precisely control crystal nucleation and growth, enabling the fabrication of millimeter-scale perovskite crystals with markedly reduced defect densities and enhanced charge transport properties.[1,2]

By employing methylamine-induced dissolution and recrystallization in combination with pre-patterned nucleation seeds, we demonstrate the formation of continuous perovskite films composed of large, well-defined crystals.[3] This approach uniquely allows the creation of stoichiometrically identical samples with systematically varied crystal size.

Leveraging this level of control, I will introduce a method to deterministically tune the number of grain boundaries within a film. This platform enables direct, quantitative investigation of grain boundary effects, including their role in processes such as ion migration.

These results establish a new experimental framework for directly disentangling structure-property relationships in perovskite materials and provide exciting insights for the design of next-generation high-performance optoelectronic devices.

A major challenge for the practical application of perovskite solar cells (PSCs) is their limited operational stability. In n–i–p device architectures, all state-of-the-art PSCs with high power conversion efficiencies (PCEs) currently rely on the benchmark hole transport layer (HTL) Spiro-OMeTAD, which is conventionally doped with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and 4-tert-butylpyridine (tBP). However, these dopants substantially compromise device stability. Furthermore, the complex in situ oxidation processes associated with conventional Spiro-OMeTAD doping obscure the underlying mechanisms, thereby hindering the rational design of stable, high-efficiency HTLs.

Here, we introduce a clean, post-oxidation-free doping strategy for Spiro-OMeTAD based on stable organic radicals as dopants and ionic salts as dopant modulators, termed ion-modulated (IM) radical doping. In this approach, the organic radicals directly generate hole polarons, resulting in an immediate enhancement of conductivity and work function, while the ionic salts further tune the work function by modulating the energetics of the hole polarons. Previously, PSCs employing IM radical-doped Spiro-OMeTAD achieved high PCEs with excellent stability, exhibiting T80 lifetimes of approximately 1200 h under 70 ± 5% relative humidity and 800 h at 70 ± 3 °C without encapsulation, effectively mitigating the trade-off between efficiency and stability. By further optimizing the dopant system, we demonstrate a significant enhancement in the thermal stability of the Spiro-OMeTAD layer, which remains stable at temperatures up to 85 °C. Moreover, the resulting HTL effectively suppresses Au migration into the perovskite layer, further contributing to improved device stability.

Halide perovskites (HPs) have emerged as a highly versatile class of semiconductors, combining strong light–matter interaction, solution processability, and a unique coupling between electronic, spin, and lattice degrees of freedom which can be chemically tailored. These properties have positioned HPs as promising candidates for spin‑based optoelectronic technologies, although toxic lead and short polarization memory currently limit their application.

In this talk, I will share recent insights from ultrafast spectroscopic studies on the role of composition and structure to control the spin-optoelectronic properties of lead-free HPs. First, I will discuss recent results on two‑dimensional hybrid organic-inorganic HPs, where the substitution of lead with germanium gives rise to strongly modified phonon coupling and emission characteristics.[1] Next, I will turn to bulk tin‑based HPs, where the reduced spin–orbit coupling relative to lead enables extended spin lifetimes.

Taken together, these studies demonstrate that lead‑free HPs constitute a promising and tunable materials platform for spin‑optoelectronic technologies.

As a novel light source technology, perovskite light-emitting diodes (PeLEDs) have achieved external quantum efficiencies comparable to OLEDs, and with superior colour space coverage. In this talk, we discuss some key considerations behind the high efficiencies and the potential mechanisms that may approach or exceed the efficiency limits. We focus on the critical challenges in this field, including device instability, brightness and downscaling. We have demonstrated, for the first time, that ultralong operational lifetimes satisfying the practical demands can be achieved in perovskite LEDs. We show that it is possible to control the polarity of charge transport in emissive perovskite semiconductors, enabling ultra-high brightness of 1.16 million nits in perovskite LEDs, setting a brightness record for solution-processed LEDs. Our efforts of downscaling micro- and nano-perovskite LEDs to below the size limit of conventional LEDs are presented, showcasing the potential of micro/nano-PeLEDs for next-generation display technologies. Finally, we present our results on the first electrically-driven perovskite laser and its potential as a new semiconductor laser technology.