Guanidinium salts are emerging as powerful chaotropic agents for next-generation perovskite solar cells, simultaneously boosting device efficiency and stability across different architectures. In inverted lead-halide perovskites, partial A-site substitution with guanidinium enhances short-circuit current and fill factor by accelerating charge transport and suppressing ion migration, delivering stable performance improvements distinct from conventional devices. In mixed tin–lead (Sn–Pb) perovskites, guanidinium thiocyanate plays a mechanistic role in crystallization, slowing crystal growth and enabling homogeneous films with suppressed nonradiative recombination. Using hyperspectral and real-time in situ photoluminescence imaging, we reveal that perovskite crystallization continues during cooldown, a previously overlooked regime that critically determines film quality. Together, these findings establish guanidinium as a versatile additive for tailoring charge dynamics and crystal growth, advancing perovskite photovoltaics towards higher efficiency and stability, while providing design principles for additive engineering across diverse material systems, processing windows, and device architectures relevant to scalable manufacturing and long-term operational reliability.

Low-dimensional metal halide perovskites are attracting great interest for photovoltaics and photonics. The type of B-site metal in conjunction with the organic templating cations play a crucial role to determine the properties of low dimensional perovskites.

Here we discuss how the molecular engineering of organic cations in terms of cationic head (ammonium vs imidazolium, mono- vs di-topic cations) as well as geometry, length and conjugation of the molecular core (alkyl vs aromatic derivatives) deeply affect the dimensionality, structural and optoelectronic properties of lead and tin perovskites. We employ solid state NMR (ssNMR) as a key technique to investigate the local structures at the atomic level via ¹H, ¹³C, ¹⁵N, ¹¹⁹Sn and ²⁰⁷Pb ssNMR spectroscopy, providing clear spectral fingerprints which are characteristic of perovskites with different structural motifs, allowing the identification of their supramolecular spatial arrangements.^[1] We further apply spin-lattice relaxation dynamics measurements to investigate molecular motions and structural rigidity in low-dimensional systems, and discuss their impact on the perovskites’ luminescence properties, relevant for lasing and photonic applications.^[2,3]

Our studies shed light on how supramolecular engineering can guide the development of improved materials for optoelectronics.

High throughput discovery in organic and hybrid photovoltaics increasingly relies on photoluminescence as a fast proxy for optoelectronic quality. Yet, once charge selective contacts are introduced, photoluminescence can become a trap rather than a guide. In our work we show that strong photoluminescence quenching can occur under open circuit conditions even for highly efficient photovoltaic heterojunctions, creating a false negative problem that can systematically eliminate the most promising interfaces during screening. We address this bottleneck by combining steady state and transient photoluminescence with contactless transient surface photovoltage on representative half device stacks. The key idea is to separate what photoluminescence cannot disambiguate on its own, namely whether quenching originates from beneficial charge extraction or from harmful nonradiative recombination. The joint readout provides a direct window into extraction dynamics and interfacial loss channels, enabling a physically grounded classification of heterojunction behavior that is compatible with rapid screening workflows. To move beyond phenomenology, we introduce a digital replica of the interface that explains why photoluminescence can remain strongly quenched after extraction. The model identifies Coulomb attraction together with interfacial recombination as the fundamental mechanisms that drive this behavior, clarifying why photoluminescence based metrics can become non predictive once selective contacts are present. Building on these insights, we present a practical decision tree for interpreting photoluminescence in the presence of selective contacts and for triaging heterojunctions toward device integration. This provides a route to unify accelerated materials discovery with accelerated device discovery, and it enables measurement protocols that are immediately relevant for data rich optimization and future self driving laboratories. The methodology is broadly transferable across photovoltaics, photodetectors, and LEDs. (https://arxiv.org/abs/2510.11548)

Perovskite photovoltaics are often assumed to require cleanroom manufacture, yet scalable production will increasingly occur in industrial environments where settled dust is unavoidable. We introduce a method that allows the quantification of how non-conductive particulates influence device formation, performance and reliability across planar and mesoscopic architectures. Using a monitored dust-circulation box to deliver reproducible particle loads, planar n-i-p devices were fabricated with dust introduced at selected interfaces in both a printed carbon contact stack and a conventional spiro/Au stack. Despite visible microstructural disruption and local inactive regions in electroluminescence maps, photovoltaic metrics showed only modest, interface-dependent losses and thermal ageing of MAPI films followed similar pathways with and without dust. In parallel, screen-printed triple mesoscopic carbon cells were assessed with dust at printing interfaces and within pastes. Here, spatial variability increased due to local print thinning, altered roughness and occasional infiltration defects observed in microscopy and cross-sections. Finally, we highlight how particle-induced shading can create local reverse bias, promoting shunt growth, and possible hotspot formation, linking manufacturing contamination to field reliability.

The growing interest in integrating semi-transparent (ST) perovskite solar cells (PSCs) into urban and agricultural infrastructures draws attention to the challenging trade-off between light transmittance and power conversion efficiency (PCE) in ST devices [1-2]. The use of transparent and conductive charge transport layers is essential for achieving high electrical and optical performance in ST-PSCs [3]. For this reason, a charge transport layer with controlled thickness and surface roughness is necessary to reduce parasitic absorption and reflection losses [4]. Indeed, the atomic layer deposition (ALD) has emerged as an effective technique for controlling both surface morphology and thickness [5]. Additionally, ALD produces compact and pinhole-free films with optimal substrate coverage. This prevents charge recombination at the interface and enhances the films' optical transparency across most of the visible spectrum [6].

In this context, the effect of TiO₂ electron transport layer (ETL) deposited by ALD in ST-PSCs is here investigated. An accurate analysis has been conducted to optimise the thickness, ranging from 5 to 20 nm, and the ALD deposition methodology, plasma or thermal, of the TiO₂ layer. The improved TiO₂ film, 20 nm thick by thermal ALD, was combined with SnO₂ thin film creating an ETL bilayer to enhance the charge extraction. In addition, different perovskite formulations were investigated to enhance both average visible transmittance (AVT) and PCE of the ST-PSCs. Comprehensive films and devices' characterization, including UV-Vis spectroscopy, scanning electron microscopy (SEM) and X-ray diffraction, helped in identifying the optimal layers for ST-PSCs.

The ALD-TiO₂/SnO₂ ETL bilayer demonstrated enhanced AVT and PCE, and a superior light utilisation efficiency (LUE=AVT×PCE) when compared, through external quantum efficiency (EQE) and current-voltage measurements, to the most common TiO₂ by spray pyrolysis (SP), also employed in a bilayer, and to the SnO₂ stand-alone ETL. Indeed, the ALD-based ST-PSC showed reduced light loss in the photon balance check (EQE+Reflectance+Transmittance≤1) and increased perovskite grain size in the SEM imaging. These results suggest that the ALD-TiO₂/SnO₂ bilayer effectively improves, at the same time, both optical transmittance and electrical performance, paving the way for ST-PSCs with balanced AVT and PCE and thus enhanced LUE values.

Perovskite solar cells (PSCs) continue to push the boundaries of efficiency and manufacturability, and much of this progress hinges on the quality of charge-transport layers (CTLs) and their interfaces with the perovskite absorber. These buried junctions govern not only device performance but also play a decisive role in long-term stability. In particular, the introduction of SnO₂ interlayers has led to significant enhancements in perovskite film stability¹. Yet depositing SnO₂ directly onto soft metal halide perovskite thin films remains a fundamental challenge, as unwanted interfacial reactions can degrade the underlying perovskite². This issue remains underexplored for wide-bandgap, bromine-based perovskites, despite the technological relevance of compositions such as FAPbBr₃ and CsPbBr₃ for tandem photovoltaics, and their interactions with SnO₂ CTLs are still poorly understood. Advanced deposition techniques, including atomic layer deposition (ALD) and pulsed laser deposition (PLD), offer precise control over film thickness and composition, yet both processes can introduce chemical and structural stresses when applied directly to the perovskite surface.

By employing a correlative multi-technique approach that integrates photoluminescence (PL) imaging with advanced photoemission spectroscopy methods—ultraviolet photoelectron spectroscopy (UPS) and hard X-ray photoelectron spectroscopy (HAXPES)—we elucidate how SnO₂ deposited by ALD or PLD on FAPbBr₃ and CsPbBr₃ affects the interfacial electronic structure and non-radiative recombination as a result of film formation and deposition-induced damage.

Grazing-incidence X-ray diffraction (GIXRD) measurements confirm that the perovskite crystal structure remains largely intact following oxide deposition. PL imaging enables quantification of the bandgap (Eg) and quasi-Fermi level splitting (QFLS), revealing composition-dependent trends in optoelectronic behavior that arise from differences in interfacial dynamics associated with each deposition method.

Quantitative fitting of HAXPES spectra at different excitation energies uncovers the chemical origins of this contrasting behavior, showing that ALD and PLD induce distinct types of surface or near-interface modifications, with the extent and nature of these effects strongly dependent on the A-site cation chemistry.

Overall, the study reveals that the A-site composition of wide-bandgap perovskites governs their tolerance to oxide deposition processes and determines whether SnO₂ acts as a benign passivation layer or as a source of interfacial degradation. These insights provide guiding principles for the design of oxide/perovskite interfaces optimized for wide-bandgap optoelectronic and tandem photovoltaic applications.

Quasi-2D/3D perovskite heterostructures have garnered considerable attention for optoelectronic applications due to their tunable optical properties and enhanced stability in comparison to their 3D counterparts [1,2]. By controlling the composition and structure of heterostructures, it is possible to engineer heterostructures for high-performance photovoltaic applications. In this study, we investigate charge transport in quasi-2D/3D perovskite heterostructures and the impact of different organic spacer cations and the incorporation of thiocyanate additive [3,4]. Using UV-Vis spectroscopy, PL hyperspectral microscopy, and Time-Resolved Photoluminescence measurements, we report differences in phase composition and morphology resulting from the different fabrication routes and observe its impact on recombination dynamics. In addition to defect passivation effects, we reveal how the thiocyanate additive regulates the dynamics of charge-carrier transfer from wide-bandgap 2D domains to low bandgap 3D perovskite. Our findings provide insights into how the choice of spacer cation and incorporation of additives in the fabrication process influence carrier transport and recombination, offering strategies for optimizing quasi-2D perovskites for efficient and stable optoelectronic devices.

Photovoltaic devices based on inorganic perovskites, such as CsPbI₃, are of great interest for various applications, including both single-junction and Si/perovskite tandem devices. The polymorphism of CsPbI₃, which can exist in four different phases, offers opportunities for novel device architectures but also poses significant challenges due to the need to stabilize the photoactive phases and prevent conversion to the δ-phase. In this talk, I will outline the crucial role that interfaces play in dictating the performance of CsPbI₃ inverted architecture solar cells and discuss strategies for improving their performance.

Improving the efficiency of solar cells is the most effective route to reduce the levelised cost of electricity, and hence accelerating installations. Tandem structures offer a route to higher efficiencies (>35%) compared with single junction cells[1]. The tuneable bandgap and long charge-carrier lifetimes of metal halide perovskites make them ideal candidates for use as the top cell in tandem architectures, however their poor stability and large interfacial energetic losses complicate commercialisation[2]. 

Passivating these interfaces is effective in energetic loss mitigation although control over repeatability can be challenging. We have developed a novel passivation route that delivers increased control in passivation efficacy, observing strong enhancements to the perovskite radiative efficiency and photoluminescence lifetimes. Using our home-built stroboscopic scattering microscope (stroboSCAT), we show that the energy transfer dynamics are enhanced in the passivated samples, elucidating microscale insights into the passivation mechanism. Finally, we fabricated full photovoltaic devices that demonstrated successful interfacial passivation with increased repeatability compared with vapour passivation, highlighting the benefit of our approach.

Metal halide perovskite materials have been widely explored in the field of photovoltaics over the past two decades. Recently, they have also been gained traction in optoelectronic memories for neuromorphic applications, such as dynamic machine vision systems [1]. Their tuneable optical properties, solution-processability, compatibility with flexible substrates and their mixed electronic-ionic conductivity, especially their slow ion migration that gives rise to a significant current hysteresis, has brought them at the forefront of beyond-CMOS materials for emerging memories with neuromorphic functionalities.

Herein I will present results from our work with Bismuth-based perovskite films in both conventional sandwich device structures [2] and in a novel coplanar nanogap device configuration [3]. We tune the cation and the solvent to move the technology towards greener and more sustainable manufacturing avenues. Our 2-terminal devices show memristive characteristics that can be controlled both electrically and optically, showing both long- and short-term plasticity. We demonstrate learning and forgetting, potentiation and depression, paired-pulse facilitation by varying the intensity and wavelength of incident optical stimulus. Finally, we showcase application of our devices in reservoir computing and obtain >95% accuracy in simulated perceptron networks.

This work paves the way to employing greener materials, such as lead-free perovskites, that can be fabricated with low-cost scalable methods and are demonstrating multiple functionalities. The perovskite volatile optoelectronic memristive devices can be used as optical reservoirs in in-sensor reservoir computing systems for application in edge artificial intelligence (AI) that can be embedded in future wearable devices and the Internet of Things (IoT).

Metal halide perovskites (MHPs) have shown remarkable potential for energy storage, with previous studies demonstrating exceptional stability enabled by protective coatings (e.g. TiO₂) on thin films [1, 2, 3]. However, translating these promising results from lab-scale demonstrations to practical coin cells with high-mass-loading electrodes presents a formidable technological challenge. At these scales, maintaining material integrity becomes critical, as uniform protective coatings via physical deposition are less feasible, and the electrode fabrication process itself can introduce severe instability.

In this work, we present a comprehensive investigation into the stability of all-inorganic lead-based (CsPbBr₃) and lead-free (Cs₂AgBiBr₆) perovskites in the context of high-loading anodes without external protective layers. We reveal that the conventional slurry-casting method -the standard protocol in battery research- is fundamentally incompatible with these sensitive materials. Through detailed structural characterization (XRD, SEM-EDS), we demonstrate that the synergistic effect of the polar solvent (NMP) and the mechanical grinding by carbon black additives induces catastrophic mechanochemical degradation.  Specifically, the carbon black acts as a grinding medium that exposes defect-rich surfaces, facilitating chemical attack by NMP. This leads to the leaching of lead and the precipitation of inactive byproducts, such as Cesium Bromide (CsBr), even before the battery is assembled or cycled.

To overcome this fabrication-induced degradation, we propose and demonstrate a solvent-free dry-processing technique utilizing hot roll-pressing. This approach successfully preserves the pristine crystalline phase of the perovskite in bulk electrodes. Electrochemical analysis confirms that the resulting dry-fabricated CsPbBr₃ anodes exhibit distinct differential capacity peaks corresponding to a reversible Li-Pb alloying mechanism, a behavior that is obscured in slurry-cast electrodes due to high polarization and material loss. Furthermore, we extended this methodology to lead-free double perovskites (Cs₂AgBiBr₆), elucidating a complex multi-phase storage mechanism involving Li-Bi and Li-Ag alloying.

Despite the preservation of the crystal structure during fabrication, the dry-processed anodes still exhibit capacity fading over prolonged cycling, attributed to active material loss and volume expansion in the absence of a confinement layer. Our findings confirm that while dry-processing is a prerequisite for fabricating functional high-loading perovskite anodes, it does not eliminate the need for interface engineering. This study ultimately underscores that achieving the long-term stability previously observed in protected thin films requires the development of scalable, chemically compatible protective strategies that can be integrated into bulk electrode manufacturing.

Metal halide perovskites have emerged as promising semiconductors that combine excellent optoelectronic properties with the advantage of low-cost and easy solution-based processing. However, most commonly used deposition methods still  rely on hazardous solvents, such as N,N-Dimethylformamide (DMF), and on wasteful laboratory-scale coating techniques like spin coating, hindering broader commercialization.

In this work we employ mechanochemistry as a  solvent-free synthesis route that enables efficient material conversion, easy scalability, and precise stochiometric control for the preparation of halide perovskites. The resulting mechanochemically derived powders are then used to formulate dispersion inks in green solvents, which are subsequently processed into films via one-step slot-die coating.

We first investigate methylammonium lead halides (MAPbX₃) as a case study. By monitoring the in-situ temperature during perovskite formation, we optimize the milling conditions and demonstrate the fabrication of efficient slot die coated detectors operating under both visible and X-ray radiation with a sensitivity of 600 μC/Gyꞏcm².^[1] We then extend this approach to a broad range of lead-free perovskite compositions, including double perovskite Cs₂AgBiBr₆ and various Sn-based materials.

Self-assembled monolayers (SAMs) based on carbazole-anchored molecules such as Me-4PACz have emerged as highly effective hole-selective contacts for high-performance perovskite solar cells (PSCs). However, the widespread use of SAMs in PSCs manufacturing has so far been limited to their conventional deposition through spin coating, which is incompatible with high-throughput and continuous fabrication. In this work, we present a comprehensive optimization, systematic analysis, and upscaling demonstration of slot-die coated (SDC) SAMs, establishing an industrially relevant pathway for large-area SAM deposition in perovskite photovoltaics.

Optimization of the slot-die coating process, including substrate to coating head gap, coating speed, and SAM solution concentration, enabled the formation of highly uniform and well-packed SAM layers. These optimized films resulted an improvement in power conversion efficiency (PCE) of SDC SAM based PSCs compared to spin-coated (SC) SAM counterparts, with the champion SDC SAM based device showing a PCE of 24.89%. The performance enhancement in SDC SAM based devices is primarily attributed to a significant rise in open-circuit voltage, indicating reduced nonradiative recombination at the SAM/perovskite interface.

A series of optoelectronic and interfacial characterizations such as impedance spectroscopy, contact-angle measurements, Kelvin probe force microscopy, surface photovoltage measurements, and morphology studies, revealed that SDC SAM layers provide superior surface coverage, improved wettability toward perovskite inks, and an increase in work function. These characteristics contribute to more efficient hole extraction and reduced interfacial recombination without altering the bulk crystallographic properties of the perovskite layer.

The upscaling capability of this method was demonstrated through uniform deposition on 150 mm × 150 mm patterned ITO substrates, yielding 36 small-area devices with excellent spatial uniformity and an average PCE of 20.6%. Furthermore, mini-modules with active area 8 cm² comprising five series-connected sub-cells achieved PCEs exceeding 22%, confirming the process compatibility with module-scale fabrication. The maximum power point tracking over a period of 450 hours showed high operational stability while retaining 95% of initial PCE in SDC SAM based devices

Overall, this study establishes slot-die coating of SAMs as a scalable, robust, and reproducible approach, offering a critical pathway toward industrial manufacturing of highly efficient and scalable perovskite photovoltaic devices.

Metal halide perovskites (MHPs) have emerged as promising candidates for next-generation gas sensing technologies, offering distinct advantages over traditional metal oxides, including room-temperature operation and low power consumption. However, achieving a balance between high sensitivity, long-term stability, and environmental safety remains a critical challenge. This work presents a comprehensive study on the design and optimization of all-inorganic MHP microcrystals for ozone (Ο₃) and hydrogen (Η₂) detection, evolving from Pb-based perovskites to eco-friendly Pb-free ones.

Initially, we investigate the impact of morphological engineering on ligand-free CsPbBr₃ crystals. We demonstrate that rounded cube-shaped (RC) microcrystals, synthesized via a facile room-temperature method, exhibit superior sensing performance compared to their well-defined counterparts. The presence of surface defects in RCs facilitates exceptional interaction with analytes, enabling the detection of O₃ concentrations as low as 4 ppb and H₂ at 1 ppm, with rapid response/recovery times [1, 2].

To further address stability and mechanistic understanding, we explore compositional tuning through mixed-halide stoichiometries (CsPbBr_3−x​Cl_x​) and Mn-doping. Our results reveal a transition from p-type to n-type sensing behavior governed by the halide ratio. Crucially, Mn-doping is found to significantly enhance the sensing response, while aging effects lead to a surprising stabilization of the material properties due to halide redistribution. These experimental findings are corroborated by Density Functional Theory (DFT) calculations, which elucidate the active adsorption sites and the role of vacancies [3].

Finally, addressing the toxicity concerns of Pb, we introduce a highly stable, Cs₂AgBiBr₆ lead-free double perovskite sensor. We compare distinct morphologies (microsheets vs. microflowers) and identify microsheets as the optimal geometry for high-sensitivity detection. This eco-friendly sensor demonstrates remarkable selectivity against interfering gases (NO, H₂, CO₂, CH₄) and maintains robust performance under high humidity and elevated temperatures [3]. Collectively, this study provides a roadmap for engineering durable, selective, and sustainable perovskite-based gas sensors for real-world environmental monitoring.

Photovoltaics (PV) is a major actor of the ongoing energy transition towards a low- carbon- emission society. Annual PV installations in 2024 reached the remarkable value of 601 GW (up from 465 GW in 2023), bringing the cumulative global PV capacity to over 2.2 TW at the beginning of 2025. This cumulative capacity should be able to supply at least 10% of the world’s electricity consumption in 2025, generating more than an expected 2950 TWh, avoiding just over 1000 Mt of CO2 emissions, equivalent to 2.8% of all energy-related emissions. Several factors lie behind the plummeting cost and fast ramp up of the PV technology. One factor is the fact that PV is modular: Identical solar panels of hundreds of watts are combined, by the dozens in rooftop installations, or by the millions in utility-scale power plants. Another successful factor relies on the possibility to adapt PV devices to different requirements realizing for example high-power modules, semitransparent PV modules, flexible products, etc..

Several semiconductor materials, realized with different processes, have been used as absorber of solar cells: today more than 98% of the overall cell production is made with crystalline silicon, while the remaining part of the production is obtained with inorganic thin film materials (manly CdTe, CIGS, and CIS). Innovative materials can contribute to the realization of the next generation of photovoltaic modules with improved performance or which can be used to integrate photovoltaics in various contexts such as the building-integrated PV or the agrivoltaics.

In this presentation an overview of the work done on the development of innovative materials and solar cells in Solar Photovoltaic Division of ENEA is reported.

Starting from our expertise on silicon-based solar cells, the research on perovskite solar cells for the development of perovskite/silicon tandem devices will be discussed. As for the bottom cell, heterojunction silicon solar cells (SHJ) realized on both p-type and n-type silicon wafers have been considered, studying also selective contacts alternative to the doped silicon thin films generally used in the current SHJ device architectures. n-i-p or p-i-n perovskite solar cells have been used for the top component, studying hybrid and inorganic perovskites deposited with different approaches (solution processes, co-evaporation, two-step, hybrid evaporation/spin-coating method), different carrier transporting layers and developing appropriate transparent front electrodes for perovskite/Si tandem cell.

 Chiral halide perovskites (CHPs) constitute an emerging class of materials that combine the remarkable optoelectronic properties of halide perovskites with chirality. This synergy unlocks advanced possibilities in chiroptics, spintronics, and next-generation optoelectronic technologies. [1] However, imparting chirality to these materials remains challenging, as intrinsically chiral perovskite emitters are rare and require precise synthetic control or advanced surface engineering.  In this presentation, I will discuss efforts to create chiral luminescent perovskite nanocrystals through surface functionalization with chiral ligands and coupling these materials to engineered chiral metasurfaces. Our strategy enables the manipulation of charge, spin, and light–matter interactions through structural asymmetry, eliminating the need for magnetic fields or low temperatures. To gain insight into the photophysics of chiral perovskites, we employ polarisation-resolved ultrafast spectroscopy, identifying distinct vibrational modes present in chiral and achiral perovskites.[2] Our results open new avenues for employing chiral perovskites in spin-optoelectronics and advanced display technologies, where nanoscale control over light polarisation is crucial for enhanced device performance and novel functionalities.

Transient photoluminescence (tr-PL) is a popular contact-less characterization method to study recombination and the properties of defects in halide-perovskite films, layer stacks and devices. Due to their low doping density, many lead-halide perovskite compositions have a complex tr-PL behavior. Here, the recombination dynamics is strongly non-linear with respect to electron density. This non-linear recombination then results in PL decays that cannot be described by either mono-exponential or multi-exponential decays leading to differential decay times that are a function of carrier density [1-2].

Whereas the tr-PL data can provide rich information about capture coefficients and defect energies, the necessary postprocessing and fitting of the data requires numerically solving a series of coupled differential equations which provides an obstacle for widespread adaptation of such models. This leads to a discrepancy in the way how spectroscopy and modeling groups analyze the data vs. how technology-focused groups analyze the data. To accelerate and greatly simplify the tr-PL data analysis while at the same time improving its accuracy, we have developed a workflow for analyzing tr-PL data measured using perovskite absorber layers that incorporates physics informed deep learning in the form of a web application called PLPal.

PLPal has an intuitive and interactive interface. The app initially performs preprocessing on the data (e.g. finding the zero of the time axis), calculates the differential decay time vs. carrier density or Fermi-level splitting automatically and then fits the data. The fitting is done very rapidly by using a convolutional neural network acting as a surrogate model [3] for the solutions of the coupled differential equations for electron and hole capture and emission via several defect states. The neural network surrogate model is combined with the Covariance Matrix Adaptation Evolution Strategy (CMA-ES) fitting algorithm to deliver high quality fits within a couple of minutes if run on a commercial laptop. Furthermore, PLPal allows the user to quantify the uncertainty of the best fit and resolves high-dimensional model parameter correlations. With the obtained tr-PL fit parameters PLPal also analyses the quasi steady-state situation to obtain an implied current-voltage curve. Additionally, we incorporated sliders for all parameters that allows the user to vary parameters of the model (like trap depth & density, capture coefficients, etc…) and see the effect on the PL transient in real time.

[1]       Yuan, Y.; et al. Adv. Energy Mater. 2025, 15 (6), 2403279. DOI: 10.1002/aenm.202403279.

[2]       Yuan, Y.; et al. Nat. Mater. 2024, 23 (3), 391–397. DOI: 10.1038/s41563-023-01771-2.

[3]       Das, B.; et al. Research Square August 11, 2025. DOI: 10.21203/rs.3.rs-7115972/v1.

The development of ever-increasing means of communication, such as 5G, and detection systems, such as military and civilian radars, is leading to an increase in the number of sources emitting electromagnetic waves and thus in strong electromagnetic pollution. This pollution can be the source of numerous interference problems between devices, as well as possible health problems. In that context, there is a strong need of new absorbent materials that are more effective and also over a wider frequency range. Hybrid perovskites (HPs), and in particular MAPI, are excellent dielectric materials displaying many polarisation modes that can be modulated according to frequency, making them excellent candidates for electromagnetic wave absorption (EMWA) application. However, EMWA testing requires a large quantity of powder to be dispersed within a polymeric matrix. Therefore, hybrid perovskites (HPs) were synthesised using mechanosynthesis, a solvent-free method that enables the production of large quantities of powders with good reproducibility and homogeneity. At first, we have studied the well-known 3D MAPbI₃ phase as EMWA materials, demonstrated an effect of grinding time and of the powder size and evidenced a broad absorption peak at 12 GHz. However, this phase suffers from a poor air stability. We therefore decided to study other HPs compositions, such as CsPbBr₃ and MAPbBr₃, which have presented a higher stability and showed new interesting absorption properties at the X band in the range 6 to 13 GHz and also Ku band in the range 13 to 20 GHz. To better emphasize their absorbing properties, we have combined these HPs with carbon-based materials to introduce new dissipation mechanisms, particularly interfacial polarisation and charge dissipation networks. We have worked at first with graphene due to its conductive properties and its already proved ability to form effective interfaces with HPs. Tests were carried out to determine the best way to integrate graphene into the synthesis process, the optimal ratio, and how to sieve and disperse the resulting powder in a polymer matrix to analyse their EMWA properties. Optimized compositions and processes have allowed obtaining Reflection Loss lower than -10 dB.

End-of-life management remains one of the most pressing technological barriers to the large-scale deployment of metal halide perovskite photovoltaics. While Pb-based perovskites enable high efficiencies with low fabrication costs, the risk of Pb leakage during disposal poses a major obstacle for their commercialisation. Developing scalable, low-impact recycling routes is therefore essential to ensure safe device decommissioning and to meet upcoming environmental regulations.

Current recovery strategies often rely on hazardous organic solvents [1-2] or yield only partial Pb recovery in water-based processes, leaving aqueous waste streams with Pb concentrations above acceptable limits (>300 ppm).[3] This gap highlights the need for environmentally benign adsorbents capable of efficiently removing Pb from perovskite dissolution baths.

In this work we explore green, water-compatible strategies for Pb recovery using metal organic frameworks (MOF) and magnetic adsorbents designed from earth-abundant, low-toxicity precursors. UiO-66 is synthesised via mechanochemistry using only 1 µL of methanol per mg of reagents. A highly crystalline material is obtained in 3 h, exhibiting negligible Zr leaching in water (<0.05%) and excellent stability under highly acidic conditions (pH < 1) and elevated temperatures (up to 400°C). Preliminary tests show modest Pb uptake in aqueous PbI2 solutions (approximately 25% removal at 250 ppm), associated with the presence of monocarboxylic acids at defect sites. Improved adsorption capacities are achieved by replacing these modulators with functional molecules that exhibit stronger affinity for Pb. In parallel, Fe3O4@zeolite magnetic composites are synthesised by growing the zeolite hydrothermally over the magnetite nanoparticles. These materials achieve 94% Pb removal from 250 ppm PbI2 solutions within 2 h, followed by rapid magnetic separation within seconds and offering potential for continuous or cyclic operation to further reduce Pb levels toward the desired thresholds.

Together, these results demonstrate the potential of combining MOF-based and magnetic adsorbents to enable fully water-based recycling processes that efficiently recover Pb while minimising secondary contamination.

Perovskite solar cells (PSCs) have been reaching unprecedented efficiencies. However, improving material systems and processes remains a complex, multi-step task, often addressed by a trial-and-error method. Yet, a crucial challenge for the commercialization of this technology remains to be the selection of solvents for depositing the perovskite active layers, for which there is currently no established methodology. Furthermore, perovskites are processed from highly toxic solvents such as N,N-dimethylformamide (DMF), with a profound negative impact on the device's environmental footprint, accompanied by hazard when aimed to large scale production. Our study presents a general semi-empirical methodology targeted for solvent selection for perovskite layer deposition to identify and evaluate potential greener candidates for replacing DMF in lead iodide-based perovskite solar cells. To demonstrate the validity of our approach, few previously unexplored green solvents were found using our semi-empirical method and employed to produce PSCs. The devices fabricated from these green solvents showed comparable or superior performance to devices processed using DMF. These results validate the method's predictive capabilities and represent a great advance towards developing more environmentally friendly processing routes for commercializing PSCs.

Hybrid and lead-free metal halide perovskites are emerging as versatile semiconductors for next-generation optoelectronic technologies, spanning photodetection, energy harvesting, and neuromorphic electronics. However, their device performance is strongly governed by defect-mediated charge transport and by the availability of scalable and environmentally sustainable fabrication routes. In this talk, I will present recent advances from our group addressing both challenges through in-situ defect spectroscopy and wafer-scale fabrication strategies for hybrid and lead-free perovskite devices.

First, I will introduce threshold voltage transient spectroscopy (TVTS), a universal and non-invasive technique that enables the real-time characterisation of trap states in fully processed multifunctional 2D perovskite devices. Applied to single-crystal field-effect transistors based on 4-fluorophenethylammonium lead iodide (F-PEAI), which simultaneously operate as high-gain photodetectors, TVTS reveals the temperature-dependent evolution of trap states from deep majority-carrier trapping at cryogenic temperatures to shallow traps above 100 K. Strong retrapping processes enhance minority-carrier diffusion lengths and enable photodetector responsivities exceeding 120 A/W, highlighting the critical role of trap dynamics in governing optoelectronic performance [1]. These findings build upon our earlier demonstrations of highly sensitive sub-wavelength hybrid perovskite photodetectors and their defect-assisted transport mechanisms [2].

I will then discuss our efforts toward lead-free perovskite platforms, focusing on both defect-mediated transport and scalable fabrication. In particular, trap-assisted transport in the lead-free 2D perovskite PEA₂SnI₄ enables neuromorphic plasticity and synaptic functionalities, illustrating the opportunities offered by defect engineering in next-generation electronic systems  [3]. Complementarily, we demonstrate the first wafer-scale, room-temperature synthesis of antimony-based perovskite analogues (Cs₃Sb₂Br₉ and Cs₃Sb₂I₉) via radio-frequency magnetron sputtering—a solvent-free, industry-compatible technique widely used in semiconductor manufacturing. These films exhibit high crystallinity, tunable optical bandgaps, and excellent optoelectronic performance when integrated into photodetectors, achieving responsivities of 3.3 A/W, bandwidths up to 11 kHz, and detectivities of 1.7 × 10¹⁵ Jones [4].

Together, these results highlight how defect spectroscopy, trap engineering, and scalable fabrication can be combined to unlock high-performance and environmentally sustainable perovskite optoelectronics, paving the way toward multifunctional devices and large-area integrated photonic systems.