Tin halide perovskites (THPs) are promising non-toxic semiconductors for photovoltaics and optoelectronics, yet their practical application is hindered by the rapid oxidation of Sn²⁺. We established design principles that simultaneously enhance the air stability and optoelectronic performance of two-dimensional (2D) Ruddlesden–Popper (RP) THPs through targeted crystal structure control with tightly-packed hydrophobic spacer cations. Building on these insights, we synthesized new quasi-2D THPs using 4-fluorophenethylammonium (4FPEA) and demonstrated minimized octahedral distortion, ideal 180° Sn–I–Sn bond angles, and amplified spontaneous emission in microflakes, indicating excellent photophysical quality. A structural survey of over 60 reported quasi-2D RP perovskites revealed three perovskite cage types with distinct distortion parameters – “tilted,” “balanced,” and “buckled” – that reflect the interplay of spacer cations and A-cations in influencing structural distortion and photophysical properties. Finally, by further tuning spacer cation functionality and organic supramolecular interactions, we found new ultrastable 2D THPs that enable high power conversion efficiency in 2D/3D tin perovskite solar cells while significantly improving air stability and device durability. These findings establish rational design principles for developing stable, high-performance lead-free tin perovskites and enabling their practical optoelectronic applications.

The quest for sustainable and non-toxic alternatives to lead-based perovskites has led to growing interest in lead-free chiral metal halides (CMHs) — a class of materials that combine structural chirality with tunable optoelectronic properties. These compounds, including both perovskite and perovskite-inspired materials, often incorporating metals such as bismuth, antimony, or copper, exhibit intrinsic circular dichroism, second-harmonic generation (SHG), and spin-selective charge transport, making them highly attractive for next-generation applications in chiroptoelectronics, nonlinear optics, and spintronics. In this work, we present the synthesis, crystallographic characterization, and photophysical behavior of several new lead-free CMHs, highlighting the role of metal center and chiral organic ligands in dictating crystal symmetry and electronic structure. Optical spectroscopy and polarization-dependent measurements reveal strong chiroptical responses and promising excitonic dynamics at room temperature. Furthermore, we discuss structure–property relationships and design principles aimed at enhancing their stability, light-harvesting efficiency, and spin filtering capabilities.Our findings demonstrate that lead-free CMHs offer a viable and environmentally benign platform for multifunctional materials design, bridging the gap between molecular chirality and solid-state photophysics.

The search for non-toxic and stable optoelectronic materials has led to increasing interest in lead-free halide double perovskites [1]. Among them, mixed-valence gold halide double perovskites Cs₂Au₂X₆ (X = Cl, Br, I) have emerged as promising candidates for lead-free optoelectronics due to their exceptional ambient stability and near-infrared band gaps [2], making them ideal for applications such as photovoltaics and infrared detectors. However, their notoriously low photoluminescence quantum efficiency continues to hinder device integration, and the fundamental mechanisms responsible for this inefficiency remain poorly understood. 

In this work, we elucidate the dominant role of electron–phonon coupling in governing the optical response of these materials through a comprehensive multi-modal spectroscopy approach combining temperature-dependent photoluminescence, absorption spectroscopy, and Raman scattering [3]. Our PL measurements reveal broad, red-shifted emission with a strong temperature dependence, indicative of carrier localization and phonon assisted relaxation processes. On the other hand, absorption spectra exhibit a pronounced urbach tail, which we attribute to lattice distortions generating polar states that act as non-radiative recombination centers. This feature plays a crucial role in non-radiative carrier trapping and contributes to the low quantum efficiency typically observed in this class of materials. 

Overall, these results provide new insight into the interplay between lattice dynamics and electronic processes in gold-based double perovskites. Beyond fundamental understanding, this work highlights the potential of gold perovskite as a model system for optimizing lead-free double perovskites and design new architectures for sustainable optoelectronics devices. 

The strategic fluorination of organic spacers in 2D tin-halide perovskites has emerged as a compelling approach to improving the stability and optoelectronic performance of lead-free materials, yet the interpretation of these effects is often complicated by rapid, morphology-driven crystallization associated with traditional spin-coating methods [1]. In this work, we investigate nanoplatelets (submicrometric in thickness and > 10 µm of lateral size) of 4-fluoro-phenethylammonium tin iodide, (4F-PEA)₂SnI₄, made by the hot injection method. Leveraging the inherently low solubility of these tin-halide perovskites in n-octane, well-defined polycrystalline films 10-20 µm thick were formed for optical characterization [2]. In the temperature range of 25–300 K, steady-state photoluminescence (PL) and Time Resolved PL (TRPL) measurements were conducted, along with PL excitation spectra at 25 and 300 K. From the PL spectra, it is evident that the spectrum is predominantly composed of two components, each peaking at 1.894 and 1.931 eV (655 and 642 nm) at 25 K. Based on PLE spectra and micro-PL imaging conducted at 80 K and room temperature, it has been determined that the low-energy PL contribution originates from exciton recombination at the center of the nanoplatelets, while the high-energy PL contribution is attributed to exciton recombination spatially localized at their contour edge [3]. From the TRPL measurements, we deduce decay times of approximately 400 and 240 ps at the high and low PL peak energies. These results are consistent with two different exciton populations: one with a two-dimensional character (located at the center of the nanoplatelet) and the second with lower dimensionality (situated at the nanoplatelet edge) [4]. Furthermore, amplified spontaneous emission (ASE) in backscattering geometry was investigated in similar films of nanoplatelets using a sub-ns pulsed laser at 532 nm with a repetition rate of 1 kHz. This investigation provides valuable information regarding the high radiative emission efficiency of these nanoplatelets. ASE is observed at the low energy side of the PL spectrum, approximately at 666 nm, where absorption is negligible. The threshold average power of ASE is 4 µW [5]. Notably, ASE is observed up to a temperature exceeding 100 K, further indicating the relatively high structural quality and reduced presence of nonradiative centers in these nanoplatelets, comparable to the state-of-the-art results in Ruddlesden-Popper perovskite phases, both lead and lead-free.

Organic–inorganic hybrid perovskites have recently emerged as compelling candidates to replace conventional semiconductors, driven by a suite of remarkable optoelectronic properties. These include broadband light absorption, tunable band gaps, high charge-carrier diffusion lengths, solution-processability at low cost, and intrinsic mechanical flexibility. However, their commercial viability is critically hindered by poor environmental stability—particularly their susceptibility to moisture, thermal stress, and photodegradation—as well as the toxicity associated with water-soluble lead compounds, posing significant ecological and health-related challenges. Substituting Pb²⁺ with homovalent (Sn²⁺, Ge²⁺) or heterovalent (Sb³⁺, Bi³⁺) cations effectively mitigates toxicity while preserving perovskite functionality. Notably, vacancy-ordered layered double perovskites (LDPs) (A₄M(II)M(III)₂X₁₂) emerged recently as a promising lead-free class, offering direct band gaps, enhanced stability, and tunable optoelectronic properties via precise divalent/trivalent cation engineering. In this study, we conducted a systematic investigation into M(III) cation engineering within the Cs₄CoIn₂Cl₁₂ LDP framework by substituting In³⁺ with Bi³⁺ and Sb³⁺. This strategy facilitated the first-ever colloidal synthesis of Cs₄CoBi₂Cl₁₂ and Cs₄CoSb₂Cl₁₂ NCs. We examined how the structural distortions arising from these substitutions influence the optoelectronic properties of these NCs, revealing that Cs₄CoBi₂Cl₁₂ exhibited superior performance, characterized by a stable photo response and enhanced photocurrent generation in photoelectrochemical (PEC) applications. Transient absorption analysis confirmed the highest population of self-trapped excitons (STEs) alongside the longest half-lifetime in Cs₄CoBi₂Cl₁₂ hosts, enabling it as a promising material for sustainable PEC applications. Additionally, all the NCs demonstrated remarkable air and compositional stability, preserving their structural and chemical integrity for over 100 days under ambient conditions.

The era of Big Data and Artificial Intelligence (AI) is generating huge amounts of data daily, posing a significant challenge for conventional computing technologies, which require high power consumption for processing. Neuromorphic computing is emerging as a new computing paradigm that offers a more efficient solution since it mimics the structure and function of the human brain, the most energy-efficient computing system known. Neuromorphic hardware requires electronic elements that emulate the synapses and other neural processes. To this end, Pb-based halide perovskite (Pb-HP) memristors are excellent candidates due to their outstanding properties, but the toxicity of Pb hinders their practical application. For the development of the technology, it is urgent to find Pb-free alternative materials that enable the fabrication of high-performance memristors.

In this presentation, we will analyze the potential of diverse Pb-free perovskite-inspired materials (based on Bi, Cu, and Zn) to fabricate efficient memristors.[1] We will discuss several strategies to enhance the reliability and energy efficiency of the devices, such as the use of inorganic and organic interfacial buffer layers.[2] To demonstrate the effectiveness of these strategies, we investigate the resistive switching properties and the synaptic plasticity of the memristors. Overall, our results highlight the potential of  Pb-free perovskite-inspired materials to fabricate efficient memristors for next-generation sustainable neuromorphic computing.

Lead-free halide double-perovskite quantum dots (QDs) with self-trapped exciton emission offer an environmentally benign platform for broadband and single-phase white-light generation. However, their practical implementation in light-emitting diodes (LEDs) remains limited by modest photoluminescence quantum yields (PLQYs), intrinsic restrictions associated with their indirect bandgap and parity-forbidden transitions, and severe charge losses arising from trap-mediated recombination and inefficient carrier transport. To address these challenges, we develop Sb³⁺/Mn²⁺ co-doped Cs₂NaInCl₆ QD inks combined with short-chain ligand engineering to simultaneously enhance their optical performance, electronic conductivity, and device compatibility [1].

The dual-ion doping strategy provides stable white emission while effectively reducing cation disorder in the perovskite lattice, yielding near-unity PLQY. Meanwhile, replacing conventional long-chain surface ligands with short-chain 2-ethylhexanoic acid and 3,3-diphenylpropylamine chloride dramatically improves charge transport in the QD films. This ligand shortening enhances conductivity by nearly twentyfold, suppresses nonradiative surface recombination, and induces favorable energy-level alignment with the poly(9-vinylcarbazole):poly hole-transport layer, thereby reducing the hole-injection barrier by approximately 0.4 eV. As a result, charge balance in the LED architecture is significantly improved, enabling efficient carrier recombination under electrical excitation.

These combined advances lead to markedly enhanced electroluminescent performance. The resulting LEDs achieve an external quantum efficiency of 0.91% (0.05 cm²), representing the highest reported efficiency for double-perovskite QD-based devices and a 1.3-fold improvement over the previous state-of-the-art. Furthermore, temperature-dependent photoluminescence measurements reveal that increasing temperature drives the gradual fusion of dual-emission bands, enabling a controllable transition from cool white to warmer pure-white emission. This tunable thermal response highlights the potential of these materials for adaptive or color-variable lighting.

Overall, the integration of controlled doping, defect suppression, and short-chain ligand engineering establishes a viable pathway to overcome the intrinsic limitations of lead-free double-perovskite QDs. These findings advance their prospects for high-quality, stable, and environmentally responsible solid-state lighting technologies.

Over the last decade, metal halide perovskite nanocrystals (LHP NCs) and their derivatives, in the form of nano and bulk crystals, have emerged as a promising class of semiconductor materials with many interesting linear and nonlinear optical properties. The light emission of LHP NCs is not only tunable by their dimensions and composition but also through self-assembly into ordered architectures. Interestingly, LHP NCs spontaneously self-assemble into superlattices and exhibit interesting optical properties such as polarized emission. On the other hand, low-dimensional metal halide crystals with chiral ligands exhibit chiroptical properties. This talk will be focused on the latest developments in achieving polarized absorption and emission from metal halide bulk and nanocrystals either by self-assembly of NCs or helical structural engineering.

Lead-free perovskite-inspired metal halides are rapidly emerging as a powerful platform for next-generation optoelectronics, offering chemical tunability, rich structural diversity, and reduced toxicity compared to their lead-based counterparts. [1, 2] Yet, fully exploiting their potential requires a mechanistic understanding of how structural dimensionality, lattice distortion, and dopant chemistry dictate their broadband emission and exciton dynamics. In this presentation, I will highlight our recent efforts to establish these structure–composition–property relationships and translate them into design principles for high-performance lead-free light emitters and sensing materials. [3-5]

We first examine the role of structural dimensionality using a family of antimony (Sb)-doped Indium (In)-based halides that possess 0-dimensional (0D) electronic structures but feature 3D, 2D, 1D, and 0D connectivity at the molecular level. [6] As the dimensionality decreases, the broadband emission redshifts continuously from about 500 to 660 nm (Fig. 1a). Through detailed structural and spectroscopic analyses, we reveal that the distortion of [SbCl₆]^3- octahedra drives this tunability (Fig. 1b). We further demonstrate that solvent coordination during crystallization provides an additional handle to tailor emission: by crystallizing [SbCl₆]^3- frameworks from hydrochloric acid (HCl), dimethylformamide (DMF), methanol (MeOH), acetonitrile (ACN) and dimethylacetamide (DMAC). We uncover solvent-dependent structural motifs where coordinated organic molecules modulate the local metal halide structures and resulting different photoluminescence. [7] Extending these principles, we introduce a broader design strategy that couples ns² ion doping with controlled lattice distortion to achieve tunable broadband emission spanning the UV–visible–NIR range within a single host.

Beyond compositional and structural design, we further probe the fundamental mechanisms governing exciton relaxation in low-dimensional lead-free metal halides, particularly their strong temperature-dependent broadband emission. Using a 1D hybrid organic–inorganic Tin (Sn) halide as a model system, we investigate how exciton–phonon coupling and lattice dynamics regulate broadband emission. Temperature-dependent femtosecond transient absorption (Fig. 1c) measurements provide direct insight into the exciton relaxation pathways, revealing a thermally activated phonon-assisted nonradiative channel. [8] We further investigate the functional role of dimensionality to exciton-phonon coupling and exciton self-trapping.

Together, these results advance the fundamental understanding of lead-free perovskite-inspired materials and establish mechanistic guidelines for their use in broadband LEDs, low-threshold lasers, and temperature-responsive photodetectors.

Tin-based halide perovskites are promising lead-free absorbers, but their susceptibility to Sn(II) oxidation make their optoelectronic properties strongly time dependent under realistic operating conditions. Rather than treating this chemically dynamic behavior solely as a stability problem, their soft lattice and defect chemistry can be leveraged to understand and ultimately control the reversible and irreversible transformations that govern device performance.

Building on this perspective, thiophene-2-ethylammonium halides (TEAX, X = I, Br, Cl) are introduced as sulfur-based additives that coordinate with Sn in the precursor solution, adjust crystallization dynamics, and inhibit Sn(II) oxidation in FASnI3 films. These interactions enhance crystallinity, increase the Sn2+/Sn4+ ratio, and suppress bulk and surface defect formation, enabling power conversion efficiencies up to about 12% and markedly improved operational stability under continuous illumination. In particular, TEABr-based devices maintain more than 95% of their initial efficiency for thousands of hours in inert atmosphere, while TEAX-treated films retain far higher Sn2+ content than control samples after ambient exposure.

Our study examines the evolution of TEAX-modified Sn-based perovskite solar cells under electrical and ambient stress, highlighting pathways of reversible performance loss and spontaneous recovery associated with defect reconfiguration, ion migration, and redox chemistry in the perovskite and interfacial layers. Incorporation of TEAI in unencapsulated FASnI3 devices enables a pronounced in operando self-healing effect, where initial degradation under 60% relative humidity is followed by performance recovery and even enhancement beyond the initial efficiency, in stark contrast to rapidly failing control cells. By combining photoluminescence with electrochemical impedance spectroscopy, the work tracks changes ative recombination and charge transport, correlating luminescence signatures with frequency-resolved resistive and capacitive responses that fingerprint distinct degradation mechanisms.

They also guide the design of additives, interlayers, and operational protocols that promote performance recovery while suppressing irreversible degradation, pointing toward robust, high-performance, lead-free perovskite devices in which chemical dynamics are monitored and actively managed rather than merely tolerated.

Lead-free hybrid perovskites have emerged as advanced materials with high potential for solar cell applications, attracting significant attention due to their high photovoltaic performance and reduced environmental impact. In this study, these perovskites were synthesized via solution-based methods with precise control over crystallization conditions. Their structural, optical, and electronic properties were comprehensively characterized using spectroscopy, microscopy, and photovoltaic measurements. The thermal and environmental stability of the materials was also systematically evaluated under varying humidity and temperature conditions to assess their effects on device performance. The results indicate that optimizing composition and synthesis conditions can simultaneously achieve high photovoltaic efficiency and long-term operational stability. This research not only advances the understanding of material properties but also provides practical insights into the design and fabrication of non-toxic, environmentally friendly perovskite solar cells, bridging the gap between material science and device applications. These findings offer new opportunities in sustainable energy and advanced functional materials.

Bifunctional Polymer-Assisted Growth of Crack-Free Thick Perovskite Films for Flexible X-ray Detection

Qianrui Li^a, Donato Valli^a,b, Elke Debroye^a*

^a Department of Chemistry, KU Leuven, Celestijnenlaan 200F, 3001, Heverlee, Belgium.

^b Institute of Supramolecular Science and Engineering (ISIS), Strasbourg, Grand Est, France

E-mail: qianrui.li@kuleuven.be

The expanding use of perovskite materials in flexible optoelectronics has sparked growing interest in their application for flexible X-ray detectors. However, developing flexible, lead-free perovskite devices remains challenging because achieving the film thickness required for strong X-ray absorption typically leads to cracking and poor device reliability.^[1]

In this presentation, I will introduce a bifunctional polymer-guided crystallization strategy to resolve the intrinsic trade-off between thickness, mechanical integrity, and charge transport continuity in Cs₂AgBiBr₆ thick films. P123 is composed of poly(ethylene glycol) (PEG) and poly(propylene glycol) (PPG), to simultaneously control crystallization and enhance the mechanical integrity of lead-free Cs₂AgBiBr₆ thick films. We demonstrated that PEG modulates precursor coordination and intermediate-phase evolution, suppressing uncontrolled nucleation, while the PPG prevents excessive Ag⁺ binding and stabilizes uniform long-range crystal growth. Together, these two molecular interactions establish a self-regulated crystallization environment that produces uniform, highly ordered, and mechanically resilient Cs₂AgBiBr₆ thick films approaching 100 µm.

The resulting P123-modified Cs₂AgBiBr₆ detectors deliver a remarkable X-ray sensitivity of 244.71 μC Gy⁻¹ cm⁻² under a low bias of 50 V mm⁻¹, more than twice that of unmodified devices based on Cs₂AgBiBr₆ microcrystals.^[2] Moreover, the detectors maintained over 70% of their initial sensitivity under small bending radii and over 80% after 500 bending cycles, exhibiting outstanding fatigue endurance and long-term stability over a 60-day period, in contrast to the pronounced degradation seen in pristine Cs₂AgBiBr₆ devices. This study establishes a polymer-guided design paradigm for fabricating lead-free, flexible, and scalable perovskite-based radiation detectors.

[1] I. López-Fernández, D. Valli, C.-Y. Wang, S. Samanta, T. Okamoto, Y.-T. Huang, K. Sun, Y. Liu, V. S. Chirvony, A. Patra, J. Zito, L. De Trizio, D. Gaur, H.-T. Sun, Z. Xia, X. Li, H. Zeng, I. Mora-Seró, N. Pradhan, J. P. Martínez-Pastor, P. Müller-Buschbaum, V. Biju, T. Debnath, M. Saliba, E. Debroye, R. L. Z. Hoye, I. Infante, L. Manna and L. Polavarapu, Advanced Functional Materials 2024, 34, 2307896.

[2] L. Clinckemalie, R. A. Saha, D. Valli, E. Fron, M. B. J. Roeffaers, J. Hofkens, B. Pradhan and E. Debroye, Advanced Optical Materials 2023, 11, 2300578.

The rapid thermalization of photoexcited hot carriers (HCs) represents a fundamental efficiency limitation in optoelectronic devices, where energy losses via ultrafast electron- phonon scattering severely constrain practical performance. The vacancy-ordered halide perovskites (VOHPs) emerge as promising candidates for HC harvesting owing to their distinctive electronic structure featuring quantum confinement within discrete metal halide octahedral units. Here, we employ state-of-the-art nonadiabatic molecular dynamics with time- domain density functional theory and machine learning (ML) to investigate HC dynamics in experimentally realized A₂SnBr₆ (A = Rb, Cs, methylammonium (MA)). The quantum confinement in these VOHPs indeed produces discrete energy states near the band edges, potentially establishing phonon bottlenecks that can substantially prolong HC lifetimes. The thermal motion of the polar methylammonium breaks the phonon bottleneck through enhanced non-adiabatic coupling, strongly accelerating HC cooling through non-radiative channels. Contrarily, non-polar inorganic cations, Rb and Cs, exhibit significantly long HC lifetimes due to suppressed lattice dynamics, maintained discrete energy states, and weakened electron-phonon interactions. Shapley additive explanations (SHAP) reveal decisive nonlinear relationships between dynamic structural descriptors and excited-state electronic properties. The MA cation-induced inter-octahedral dihedral distortions emerge as one of the dominant features that accelerate the hot electron cooling in MA₂SnBr₆. However, thermally induced geometric variations play a minor role in altering the electronic and non-adiabatic processes in inorganic A-site cation-based VOHPs. These insights establish fundamental principles for strategic A-site cation engineering in lead-free perovskites to tailor the HC lifetimes, offering a transformative pathway towards high-efficiency optoelectronics.[1]

Metal halide perovskites are outstanding materials for photovoltaics due to their excellent optoelectronic properties, such as direct band gaps, large absorption cross sections and long lifetimes and diffusion paths of the photo-generated charge carriers. Lead-based perovskites dominate the field by providing efficiencies of 26% in solar cell devices, but an increasing interest is arising in the development of tin-halide perovskites (THP) to replace toxic lead and reduce the band gap of the perovskite. Despite large efforts, the efficiencies of THPs are still sensibly lower than the lead-counterpart, mostly due to the native p-doping and the easy oxidation of tin(II) to tin(IV), compromising not only efficiency but also the long-term stability of the material.[1] Understanding the origin of such limitations and elaborating effective strategies to improve efficiency and stability are essential for an advancement in the field.  

In this presentation we provide a theoretical perspective of the fundamental properties of THPs by focusing on the microscopic origin of the p-doping, the role of chemical composition, as well as the potential strategies which can be adopted to increase efficiency and stability. Our analysis starts from the discussion of the defect chemistry of THPs by keeping a comparison with lead. The defect-related origin of the heavy p-doping and the parallel existence of non-radiative recombination channels, as well as the potential defect-activated degradation processes at the surface will be discussed.[2-3] The role of electron-phonon coupling in tuning the localization of the hole charge carriers (free carrier vs polaron) vs the doping density is analyzed.[4] Hence, the discussion moves to elucidate the mechanisms of action of some additives commonly used in the synthesis of THPs, such as SnF2 and EDAI2, in order to illustrate how they can mitigate p-doping and improve crystallization. In-silico designed de-doping strategies based on the incorporation of trivalent metal ions coupled to small halide-alloying will be presented.[5] Finally, we will discuss the physical and chemical properties of the interface between the THP and some SAM hole transport materials, e.g. MEO-nPACZ, by illustrating the effects of the SAM and perovskite chemical composition on the electronic alignment at the interface.

Tin perovskite solar cells are emerging as the most promising non-toxic alternative to lead perovskites due to their suitable band gap and excellent charge transport properties. However, their performance still lags behind lead perovskites, primarily due to the low energy barrier of Sn²⁺ oxidation. A key contributor to this oxidation is the use of dimethyl sulfoxide (DMSO), the solvent widely used for tin-PSCs processing. Although it regulates the crystallisation dynamics, it oxidises Sn²⁺ to Sn⁴⁺, which results in self p-doping, limiting the performance of tin-PSCs. Besides, it also induces several detrimental effects, such as catalysing the deprotonation of A-site cations, promoting interfacial void formation, and facilitating iodine extraction from the perovskite film, eventually leading to device degradation. Therefore, DMSO-free processing route is crucial for efficient tin-PSCs. We have demonstrated an alternative solvent system, a mixture of DEF (N,N-Diethylformamide) and DMPU (N,N′-Dimethylpropyleneurea) for tin-PSC fabrication, which can completely supress the Sn²⁺ oxidation. ^[1,2] Although this DMSO-free route mitigates chemical instability, it introduces challenges in crystallisation control, often leading to poor film microstructure. Therefore, we employ various approaches such as composition, additive, and interface engineering to control the crystallisation dynamics and minimise the defect formation. Recently, we have achieved PCE of 10.7% by substituting formamidinium with methylammonium cation, which suppresses the lone pair expression and enhances the efficiency. Importantly, it retains 100% of initial PCE after 500 hours of day-night cycling, indicating excellent long-term operational stability. These findings highlight the crucial role of DMSO removal for achieving stable tin perovskite solar cells.

Metal halide perovskites have emerged as versatile semiconductors with promising applications beyond photovoltaics, including photodetectors, X-ray detectors, lasing and photocatalysis. A major limitation, however, is their poor stability under environmental stressors such as moisture and water . Tuning the A-site cation is a well-established strategy to improve structural stability. Dimethylammonium (DMA) has shown effectiveness in tin-based perovskites, and both DMASnI₃ and DMASnBr₃ have been reported to exhibit structural stability in aqueous environments.^[1,2] Yet, recent evidence shows that thin films of DMASnBr₃ dissolve in water in less than a minute.^[3] 

In this work, we investigate the reversible and irreversible structural changes of DMASnX₃ under different atmospheres, including O₂, ambient air and water (X= I and Br). We demonstrate that water resistance is highly dependent on morphology and particle size. While single crystals and microparticles of DMASnX₃ withstand water exposure for several hours, fine mechanochemically synthetised powders (ca. 300 nm) dissolve in water, mirroring the behaviour of thin films. We present a detailed study on the particle size-dependent stability  and show how these insights guide the development of materials capable of surviving aqueous environments for hydrogen evolution in photocatalytic systems.

As the number of Internet of Things (IoT) devices continues to grow, the demand for sustainable and maintenance-free energy solutions becomes increasingly critical. In particular, approaches that decrease dependence on traditional power supplies and mitigate the need for battery replacement are essential for a long-term IoT deployment. In light of this, we present a study assessing the industrial viability of perovskite-based solar energy harvesting for powering indoor IoT nodes. We developed a low-power sensor platform based on the EMB1061 SoC, incorporating Bluetooth Low Energy (BLE) communication to create an app for real-time power consumption monitoring, alongside high-precision HDC2080 and SHT4x temperature and humidity sensors. A key design feature for this node is the replacement of traditional chemical batteries with a 50F supercapacitor, chosen for its superior lifecycle and environmental sustainability.

The photovoltaic cell used in this work was a Pb-Free perovskite minimodule. The scale-up from laboratory Perovskite Solar Cells (PSCs) to Perovskite Solar Modules (PSMs) involves the setup of series connected devices, which enables the achieving of higher voltages compared to single cells. This connection is established by the selective etching of the specific layers that make up the PV device using a laser scriber, following the procedure described in [1].

To optimize energy harvesting, a Maximum Power Point Tracking (MPPT) circuit utilizing the off-the-shelf bq25504 controller was implemented. The system’s temporal behavior was characterized under standard indoor lighting conditions (600 lux). Baseline measurements indicated a system consumption of approximately 0.03 mAh, resulting in an estimated autonomy of 370 hours using a fully charged 50F capacitor without additional harvesting.

Comparative evaluations of the energy-harvesting configurations revealed distinct performance outcomes between the tested photovoltaic technologies. Under 600 lux illumination, a silicon-based cell coupled with the MPPT achieved a net surplus of 0.007 mAh relative to system consumption, theoretically enabling endless operation under constant illumination. In contrast, the specific perovskite configuration tested at the same 600 lux generated a maximum power output of 0.006 mW, which was insufficient to meet the active load. Furthermore, the total consumption rose to 0.031 mAh due to MPPT overhead, slightly reducing the autonomy to approximately 358 hours, around 15 days of continuous operation. However, stress tests with high illuminance (5000 lux) showed that the additional current injected reduces consumption to 0.013 mAh, which confirmed the functional viability of the perovskite MPPT integration. That suggests that either higher illumination levels, an increased active cell area, or higher power conversion efficiency will be required to achieve full energy neutrality in future designs..

This work highlights the critical trade-offs between cell efficiency, surface area, and illumination levels required for transitioning perovskite technology from laboratory settings to functional indoor IoT applications.  

Hybrid inorganic-organic perovskites are among the most sought-after materials for a diverse range of applications, including solar cells, X-ray scintillators, light-emitting diodes, electrochromic devices, photodetectors, sensors and photocatalysts. Owing to exponential growth in 5G and IoT technologies, the need for integrable and efficient energy conversion devices is increasing. This allows the use of piezoelectric nanogenerators (PENGs) as smart, wireless, portable electronic systems and sensors. The devices leverage the piezoelectric properties of perovskite materials to convert mechanical stimuli into electrical signals. In this presentation, we show that the α–FAPbI3 (perovskite phase) can be stabilized at room temperature, employing polymer additive engineering to form the FAPbI3–Polymer composite. By employing excess halide (AX) alongside a polyvinylidene difluoride (PVDF) host, both surface passivation and spatial confinement occur during co-crystallization. Investigations on the interactions between the -CF2 dipole of PVDF, the coordination-unsaturated Pb2+ defects, and the passivation of the shallow halogen vacancies[20] in perovskites without disrupting their crystallisation. The co-crystallisation of electroactive polymers in conjunction with low-dimensional metal halides is a promising approach to co-passivate, quantum-confine, and spatially trap excitons, leading to a composite material system with ultra-bright luminescence, near unity PLQY, and significantly reduced thermal quenching. The free-standing film remains stable even after a year under ambient room conditions. Along with this, we show that using lead free alternatives, the polymer composites can be used to make self-powered sensors.

Perovskite solar cells (PSCs) offer great potential in photovoltaics, they can in fact facilitate accelerated energy transition due to their low manufacturing cost and high photoconversion efficiency that is comparable to that of silicon-based conventional solar cells [1-4]. The problem of stability and lifespan continues to be a significant obstacle for this new technology, despite the remarkable recent efforts by researchers to enhance PSC performance utilising non-toxic and non-corrosive ingredients. As a result, some researchers have examined the contribution of various electron transport layers (ETLs), while others have focused on the effects of various hole transport layers (HTLs) to solve these issues [5].

This work proposes a hybrid perovskite solar cell (HPSC) architecture, based on CsSn(I_1-xBr_x)₃ and designed using a deep learning (DL) approach, by replacing the existing hole transport layer (HTL) with a tiny highly doped silicon (Si⁺⁺) layer. Electrical parameters (open-circuit voltage (Voc), short-circuit current (Jsc), fill factor (FF), and power conversion efficiency (PCE)) of this new HPSC, used to train the model, were generated using the SCAPS-1D code [6] due to its high accuracy when benchmarked to experiments. In view of the long simulation runs required, a few combinations of variables such as the bromine composition (x), metal contact work function, absorber layer, and silicon layer thicknesses, were generated and used as input parameters to build the model. Performance metrics of the model based on a Multilayer Perceptron (MLP), like the R-squared coefficient (R²), the root mean squared error (RMSE), the correlation coefficient (r), mean absolute percentage error (MAPE), and accuracy (MAE) were calculated, while the cross-validation (CV) scores were used to check the stability and the overfitting.

The best performing model had R², r, RMSE, MAPE, MAE and CV equal to 0.92, 0.96, 1.58, 0.0063, 0.36, 0.86, respectively, demonstrating the model's good predictive quality. To identify the most suitable device structure for the best performing HPSC, 21 values of each input parameter were created, for a total of 21x21x21x21 = 194,481 different device configurations. Subtracting the actual data used for training, 192,981 potential samples were obtained . The best performing HPSC was obtained by considering the highest efficiency, within the Shockley-Queisser limit. It was found to have an efficiency of roughly 26.92% for 55% bromine fractional composition, 6.2 eV metal contact work function, 1400 nm and 95 nm as absorber and silicon thicknesses, respectively. Results also indicate that the use of highly doped silicon as a hole transport layer (HTL) facilitates the extraction of photogenerated carriers and reduces the series resistance of the HPSC because of its high hole mobility of about 443 cm²/Vs, compared to most existing HTLs.