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The unproven durability of perovskite photovoltaics (PVs) is likely to pose a significant technical hurdle in the path towards the widespread deployment of this burgeoning thin-film PV technology. The overall durability of perovskite PVs, which includes operational stability, is directly affected by the mechanical reliability of metal-halide perovskite materials, cells, and modules, but this issue has been largely overlooked. Thus, there is a sense of urgency for addressing the mechanical reliability issue comprehensively, and help perovskite PVs reach their full potential. This presents many challenges, but it also offers vast research opportunities for making meaningful progress towards more durable perovskite PVs. Here I will highlight the important challenges and opportunities, together with best practices, pertaining to the three key interrelated elements that determine the mechanical reliability of perovskite PVs: (i) driving stresses, (ii) mechanical properties, and (iii) mechanical failure. I will also present examples of approaches to mitigate failure and extend the durability of perovskite PVs.  

Metal halide perovskites are characterized by tunable bandgaps obtained by varying mainly the halide composition. CsPbBr₃ and FAPbBr₃ are typical example of this class of materials with gaps exceeding 2 eV. The ability to continuously adjust the bandgap of halide perovskite materials across a broad spectrum facilitates the development of semi-transparent solar cells and modules with high visual transmittance, a technology that can be exploited for building-integrated photovoltaics (BIPV). Through bandgap optimization, tandem configurations with NIR organic solar cells can be designed to enhance efficiency without compromising average visual transmittance (AVT) [1]. This presentation highlights the EU CITYSOLAR consortium’s progress in surpassing the state of the art, showcasing diverse fabrication techniques, from solution processes to physical deposition, for see-through photovoltaics. Beyond solar cells, module-level developments, including a low-temperature, full blade-coating method for depositing semi-transparent FAPbBr₃-based perovskite modules on 300 cm² substrates [2] and innovative coupling between top perovskite module and bottom organic module are discussed. As a byproduct of this development, we show that wide-band gap perovskite such as FAPbBr₃ are excellent X-Ray detectors with record bulk specific sensitivity exceeding 7.2 C Gy−1 cm−3 at 0 V.

The exceptional properties of metal halide perovskites make them ideal materials for photovoltaic applications, with the promise to completely disrupt the areas of building-based, utility scale, and space-based photovoltaic. However, the fundamental principles of microstructure formation, evolution, and stability that are crucial for designing functional perovskite devices are understood only weakly. Currently, this is the only remaining bottleneck for the lab-to-fab transformation and realization of the scalable manufacturing of these materials. In this talk, I will discuss the potential of machine learning-driven high throughput automated experiments to expedite the discovery of metal halide perovskites, optimize processing pathways, and enhance understanding of formation kinetics^1-5. Additionally, I will showcase how high throughput automated synthesis provides a comprehensive guide for designing optimal precursor stoichiometry to achieve functional quasi-2D perovskite phases in films capable of realizing high-performance optoelectronics^3,4. I further introduce the concept of co-navigation of theory and experiment spaces to accelerate the discovery and design of metal halide perovskites. These studies exemplify how a high-throughput automated experimental workflow effectively expedites discoveries and processing optimizations in complex materials systems with multiple functionalities, facilitating their realization in scalable optoelectronic manufacturing processes.

Halide perovskites are exciting new semiconductors that show great promising in low cost and high-performance optoelectronics devices including solar cells, LEDs, photodetectors, lasers, etc. However, the poor stability, particularly ion migration, is limiting their practical use. In this talk, I will present our recent efforts in the synthesis and fabrication of lateral and vertical 2D perovskite epitaxial heterostructures and the use of these heterostructures as diffusion couples to quantitatively understand the ion diffusion and migration behaviors. Ion diffusion and migration were induced via heat, light, and bias; and the diffusion and migration were visualized via advanced photoluminescence and X-ray fluorescence mapping techniques. Through introduction of pi-conjugated bulky organic cations, enhanced stability and suppressed ion migration were observed. These findings provide important fundamental insights into the immobilization of ionic species and stabilization of halide perovskite semiconductors and demonstrate a materials platform for complex and molecularly thin superlattices, devices and integrated circuits.

Perovskite-inspired materials (PIMs) comprising Group VA pnictogen cations, such as antimony (III) (Sb³⁺) and bismuth (III) (Bi³⁺), have recently gained popularity as eco-friendly and air-stable absorbers [1]. Among them, two-dimensional Cu₂AgBiI₆ (CABI) [2] and A₃Sb₂X₉ [3] possess quasi-direct to direct bandgaps suitable for photovoltaic and other optoelectronic device applications [1]. Nevertheless, PIMs often crystallize in disordered structures with a large number of surface defects/vacancies and grain boundaries, which explains their modest performance as photovoltaic absorbers.

Recently, we have employed several compositional engineering strategies to enhance the intrinsic defect tolerance of pnictogen-based PIMs at each of the crystallographic sites (A, B, X) of the PIM structure. In this talk, I will present our most recent findings on cation and/or anion mixing in bismuth-based PIMs. In particular, I will discuss the effect of composition engineering on film morphology, structure, charge carrier transport, and properties of corresponding photovoltaics. These studies highlight the significant yet unexplored potential of pnictogen-based halides for low-toxicity and air-stable optoelectronics with competitive performance.

Metal-halide perovskites (MHP) stand out as highly promising and cost-effective optoelectronic materials due to their exceptional optoelectronic properties and versatile fabrication methods [1-6]. These materials find applications in diverse fields such as solar cells, light-emitting diodes, photodetectors, and even quantum emitters. Quantum confinement can unveil unexpected and advantageous characteristics, leading to the development of high-performance devices.

One approach to induce quantum confinement involves creating layers of quantum-confined materials through the deposition of multiple thin films. [7-10] Thermal evaporation emerges as a particularly promising technique for fabricating halide perovskite films, offering precise control over layer thickness, fine-tuning of composition, stress-free film deposition, and the ability to modify surface properties. The use of thermal evaporation in perovskite fabrication has expanded the possibilities of thin film production, showcasing its capability to generate ultrathin perovskite films that serve as the foundation for multi-quantum well structures.[11]

This method enables the manipulation of growth properties, influencing the optoelectronic characteristics of nanoscale thin films and inducing quantum confinement effects within the structure. The precise control over photoluminescence through quantum confinement opens up a wide array of possibilities for unconventional optoelectronic properties and novel applications of perovskites.

1. J. Li et al; , Joule 2020, 4, 1035

2. H.A. Dewi et al., Sust. Energy & Fuels. 2022, 6, 2428

3. E. Erdenebileg, et al Solar RRL, 2022, 6, 2100842

4. HA Dewi, et al., Adv. Funct. Mater. 2021, 11, 2100557

5. J.Li et al., Adv. Funct. Mater. 2021, 11, 2103252

6. E. Erdenebileg et al., Material Today Chemistry, 2023, 30, 101575

7. E. Parrott et al. Nanoscale, 2019, 11, 14276

8. KJ Lee et al., Nano Letters, 2019, 19, 3535

9.  KJ Lee et al., Advanced Materials, 2021, 33, 2005166

10. T. Antrack et al., Adv. Sci. 2022, 9, 2200379

11. L.R. White et al., ACS Energy Letters, 2024, 3, 835-842

Lead-tin (Pb-Sn) perovskites are a highly promising composition for single-junction and all-perovskite tandem solar cells due to their narrower bandgap and reduced toxicity. Recently, a series of strategies including interface passivation and improved crystallization have been devoted to reducing p-type doping and non-radiative recombination, resulting in record efficiencies (> 23%). However, the road towards commercialization of perovskite solar cells requires more efforts towards developing scalable deposition techniques and stable systems. The use of quasi-two-dimensional (quasi-2D) phases has resulted in superior stability towards the environment and large improvement in the crystallization with respect to the 3D compositions. Here, quasi-2D Pb-Sn perovskite is successfully prepared by a two-step blade coating. A record power conversion efficiency (PCE) of 15.06% is obtained with the in-situ passivation with tin selenide (SnSe). Furthermore, we introduced a new solvents (2-Methyl-2-butanol) in the second step, further promoting the PCE above 16%. We believe these results pave the way for the development of stable and environmentally friendly perovskite devices with scalable strategy.

Perovskite solar cells currently face challenges in terms of stability within their existing architecture. The commonly used hole transfer materials in inverted perovskite solar cells typically consist of organic compounds such as PTAA and SAM [1]. In our research, we have developed a new treatment procedure for NiO, a promising inorganic hole transfer material, which significantly improves the stability of perovskite solar cells. Our findings demonstrate the exceptional long-term aging performance of doped NiO with an insignificant loss of less than one percent over 3000 hours.
To investigate the underlying factors responsible for the observed stability enhancement, we conducted a comprehensive analysis employing various measurements, including Kelvin Probe (KP), Ultraviolet Photoelectron Spectroscopy (UPS), Atomic Force Microscopy (AFM), Time-Resolved Surface Photovoltage (TRSPV), and Time-Resolved Photoluminescence (TRPL).
Through our study, we have successfully demonstrated that our new treatment method for NiO facilitates improved hole extraction and mitigates the accumulation of free charges within perovskite solar cells. The boosted stability is primarily attributed to the optimized properties of NiO as a result of our treatment procedure.
In conclusion, our research presents a significant advancement in perovskite solar cells by introducing a novel treatment method for nickel oxide. The achieved stability enhancement through this method offers promising prospects for the commercial viability of perovskite solar cells.

Solution-based approach used to fabricate hybrid halide perovskites (HPs) induces polycrystallinity in the layer so that a massive amount of defects (10 16 cm ^-3 ) is generally formed, with a consequent detrimental effect on the open circuit voltage (Voc ) of the respective perovskite solar cells (PSCs). To face this issue, surface passivation of HPs has been improved and large organic salts are ranked among the best candidates to perform it [1]. Unfortunately, the exploration of a plethora of organic salts is driven by the trial-and-error approach, which is time and money-consuming, with limited insight into the organic salts’ features which most affect the effectiveness of the passivation. In this context machine learning (ML) methods may emerge as a valuable tool to guide experimental efforts thanks to a deeper comprehension of the passivation mechanism itself. In this study, we propose a ML approach with Shapley additive explanation to get the organic cation’s features governing the Voc optimization. We found that low halide fraction and hetero atom carbon ratio correlate with increased PSCs Voc. Through optical and morphological characterization of HPs, we concluded that the beneficial role of low halide fraction is dominated by the light Cl- , whose, with its strong binding capacity to positively charged defects in HPs, reduces non-radiative recombination, while the low hetero atom carbon ratio affects the increased flexibility of the molecule, resulting in better coverage of the surface. Finally, we assessed and confirmed the force of the ML algorithm, by using it directly to make predictions about the experimental Voc that would obtain a PSC in which the HP is passivated with a new cation [2].

[1] Sam Teale, Matteo Degani, Bin Chen, Edward Sargent, Giulia Grancini, Nature Energy, accepted
[2] Mattia Ragni, Fabiola Faini, Matteo Degani, Ian Postuma, Giulia Grancini, submitted

Organic molecules, bearing strongly electron-withdrawing CF₃SO₂^- (TFSI^-) groups, have been widely used to enhance the photoluminescence of metal dichalcogenides through electrostatic doping, without any chemical passivation, as well as to passivate traps in silicon and InAs [1]. Likewise, TFSI has been adopted for p-doping in typical organic semiconductors such as carbon nanotubes, polymers and small molecules such as spiro-MeOTAD [2]. However, these pseudo-halogen anions have never been systematically tested to modify the surface of a metal halide perovskite film in an optoelectronic device.

Here, two TFSI-based compounds with strong acidity (trifluoromethanesulfonimide and n-phenyl-bis(trifluoromethanesulfonimide) are used in order to post-treat the surface of n-doped lead halide perovskite films. Indeed, steady-state and transient photoluminescence spectroscopy proved the passivation effect of the non-halogen anions. XPS and FTIR analysis proved the interactions between –C-F and S=O groups of the non-halogen anion with both ammonium (methylammonium and formamidinium) and Pb²⁺ cations. As a result, TFSI-treated perovskite solar cells have shown enhanced stabilized power output efficiencies in a solar cell configuration and improved operational stability under typical thermal stress. This work paves the way for the use of (super)acids as excellent passivators of lead halide perovskites.

Recent breakthroughs have pushed the conversion efficiencies of organometallic lead halide thin films to 25.7% in a remarkably short timeframe. Semi-transparent perovskite solar cells show excellent potential in terms of both average visible transmittance and color neutrality, making them ideal for Building Integrated Photovoltaics. Mixed bromide-chloride perovskites allow the optical bandgap (2.3-3.0 eV) to be tuned by changing the chloride percentage, thus defining a new state-of-the-art for semi-transparent modules.[1,2]

In this work, we present the excited-state properties of a thin film of FAPb(Br_1-xCl_x)₃ perovskite with different chlorine percentages (0%<x<25%) studied by combining steady-state and time-resolved spectroscopies with theoretical analyses. Our investigation elucidates how the chemical composition induces specific modifications in the electronic bands and recombination rates of these materials.[3]

Here, we present the excited-state properties of thin film of mixed bromide-chloride perovskites studied combining steady-state light absorption, photoluminescence (PL), femtosecond transient absorption spectroscopy (FTAS), photoelectron spectroscopy (PES) with density functional theory (DFT) calculations. In this way, we give a complete description of the electronic properties of the materials, assigning the electronic bands involved in the photoexcitation by UV-Vis radiation and the relative carrier dynamics. By gathering all this information together, the performance of the different materials within a solar cell device was accurately predicted and compared with electronic characterization of working devices. In particular, we have correlated crucial figures of merit, such as PCE and LUE, with the optoelectronic properties, such as electronic band structure and carrier recombination rates.

The development of emerging photovoltaic technology has promoted the innovation of buildingintegrated photovoltaics (BIPV), not only in lower cost and simpler processing technology but also in a variety of additional features, such as flexibility and transparency. Semi-transparent solar cells that allow partial transmission of visible light are excellent candidates for BIPVs owing to their unique properties and potential for integrated energy solutions.[1], [2] In this work, we present a straightforward and highly reproducible protocol for depositing extremely uniform and ultra-thin perovskite layers. Our solution-processed perovskite solar cells, fabricated on flexible polymer substrates with large active area (1 cm2), achieved a noteworthy 5.7% power conversion efficiency (PCE) under standard conditions (AM 1.5G radiation, 100 mW cm-2) accompanied by an Average Visible Transmittance (AVT) of 21.5% for full device architecture with 10 nm thick silver electrode. We present a simple yet elegant fabrication procedure for semi-transparent perovskite solar cells without any additional antireflective layers. Furthermore, we fabricated working perovskite solar cells with the thinnest active layer of spin-coated MAPbI3 reported so far (10 nm) exhibiting 1.9% PCE and 41.1% AVT (62.9% AVT without electrode). These results hold great promise for the integration of perovskite-based semi-transparent solar cells into real-world applications, advancing the landscape of renewable energy.

Ion migration causes degradation of perovskite solar cells. Ions are moved easily, with only a few hundred meV activation energy. Still, ions move many orders or magnitude more slowly than charges in metal halide perovskites. We use this difference in timescales to imprint memory in a resistive device. These memristors can be used in neuromorphic devices to perform some computational tasks with very high energy efficiency. Because ions take very little energy to move, switching a memristive state in a perovskite device can also be very energy efficient. We show an artificial synapse that takes only a few hundred femtojoule to switch its resistive state[1]. This is achieved by downscaling the device to the micrometer scale. To avoid damage to the perovskite during lithography, we use a novel back-contact architecture for these devices. We further discuss the working mechanism of these devices. Likely the switching is achieved by filamentary formation. This mechanism would also allow to built artificial neurons. With a memristive device and an artificial neuron, full hardware neural networks could be built. If time allows, I will also briefly discuss the implications of such filament formation on solar cell stability. We observe these filaments in lateral devices, and we see evidence for permanent, dramatic voltage-bias induced damage.

References: [1] Preprint: http://dx.doi.org/10.2139/ssrn.4592586

2D Ruddlesden-Popper perovskite phases in solar cells have been exploited in combination with polycrystalline (PC) 3D HPs as ultrathin passivation layers to improve stability and charge extraction. Most of 3D/2D heterostructures reported so far are made by PC thin films grown on top of PC 3D HPs, with little control over orientation and crystalline phase, thus creating high concentration of defects at grain boundaries and interfaces, which favors the presence of traps for charge carriers, ion migration and water permeation.

On the other hand, pure 2D HPs in solar cells have been considered less suitable for photovoltaics due to their large exciton binding energies which should hinder charge separation by a significant energy loss. Surprisingly, the presence of large polarons, that is charge carriers coupled to lattice deformations, inhibits the formation of excitons and appears to be the microscopic mechanism enabling efficient 2D HPs solar cells [1,2].

The use of single crystal (SC) HPs both for 2D/3D heterostructures and pure 2D film devices is still challenging and their performance is even lower than PC devices due to the high density of traps at the crystal surface.  

Here we explore single crystal perovskite 2D perovskites and 2D/3D heterostructures. Growth of 2D HPs single crystal thin films is shown with several additives and their optical and structural properties are studied. Single crystal 2D/3D thin film heterostructures are also shown and various strategies for interface engineering are proposed. A critical comparison of the photophysics and transport properties of single crystal and polycrystalline samples is also shown.

Replacing lead by less toxic elements remains a major challenge for the widespread uptake of perovskite-based technologies. Tin appears the only candidate to replace lead, due to the accidentally similar structural and electronic properties of these two elements. A major difference, however, is the stability of Sn(IV) phases, which are related to the lower oxidation potential of tin compared to lead. A related phenomenon is the stability of tin vacancies, which introduce significant p-doping in tin-halide perovskites (THPs), while their lead-based counterpart are essentially intrinsic semiconductors. Defect activity clearly controls doping and could also contribute to the instability towards Sn(IV) phases. Controlling doping and defect activity thus represents a pathway towards obtaining stable THPs with optimal optoelectronic properties. The different defect activity of tin- and lead-based materials is at the origin of their respective thermal and phot-induced degradation phenomena, including halide demixing and loss of I₂ in lead-halide perovskites. 

Here we present results of advanced modelling studies on the defect mediated degradation pathways of prototypical THPs. We show how Sn-vacancies are central in promoting both material p-doping and formation of Sn(IV) phases. Interestingly, while p-doping dominates in the bulk, Sn oxidation is only favoured at surfaces or grain boundaries. Thus achieving uniform thin films coupled with proper surface passivation strategies represent a pathway towards achieving more stable THP-based devices. Surprisingly, THPs have also received a large attention because of their superior stability in water environment compared to their lead counterparts. We further unveil the key factors determining the stability of mixed-halide THPs against photoinduced halide segregation phenomena. Molecular and ionic strategies to mitigate p-doping in THPs are also presented.

Hybrid perovskites are well known for their excellent optoelectronic and transport properties and to the high tolerance to electronic defects.  These crystalline semiconductors also show intriguing properties (e.g. electrocaloric response, resistive switching, ferroelectric/electret states, etc.) involving the ionic dynamics at several timescales from picoseconds to micro/milli seconds (e.g. the reorientation of molecular cations, the diffusion and trapping/detrapping of charged defects, etc.) that are typically activated by temperature or external bias. The microscopic study of such phenomena is typically out-of-reach of ab initio methods due to the associated computational cost and requires alternative approaches such as classical molecular dynamics whose numerical cost scales linearly with the number of atoms.

In this lecture, it will be discussed the progress on physics-based models¹ as well as advanced machine learning approaches² for the large scale molecular dynamics simulations. Showcase applications will be presented based on the MYP potential related to the mobility of ionic defects and their interaction with surfaces³ or boundaries⁴ in lead and tin based systems. Finally, recent improvements for the study of crystallization and complex 2D/3D interfaces will be discussed.

Metal Halide perovskites have emerged as highly promising candidates for photovoltaics with the certified record power conversion efficiency (PCE) reaching 26.1% for single-junction perovskite solar cells (PSCs)[1]. However, to date, most of the reported highly efficient PSCs were obtained based on the regular n-i-p architectures at the laboratory scale, i.e., typically ~0.1 cm² [2-5], which are not suitable for upscaling. Inverted p-i-n cells, on the other hand, are attractive for upscaling due to their architecture simplicity at relatively low material cost and potentially high stability, however, their PCE still lags behind the n-i-p counterparts [6,7]. Therefore, our work has been focused on improving the efficiency of p-i-n cells and scaling them to produce efficient and stable modules. To push the PCE of cells, we developed a dual interface passivation strategy which led to a champion PCE of 24.3% for small-area cells and a champion PCE of 22.6% for a 3.63 cm² mini-module. Next, we developed a bladed-coated interlayer to passivate the NiOx/perovskite interface. As a result, PCEs of 21.8% and 20.5% are demonstrated for cells of 0.13 cm² and 1 cm², respectively. The scalability of this p-i-n architecture is successfully demonstrated, achieving aperture area module efficiencies of 19.7%, 17.5%, and 15.5% for minimodules of 4 cm², 16 cm², and 100 cm², respectively. Furthermore, we have upscaled up our baseline process and device stack to large-area modules. We fabricated bi-facial (781 cm2) perovskite solar modules exhibiting a power conversion efficiency of 16.3%, respectively. Moreover, the bi-facial mini-module retained ~ 92% of initial PCE after 1000 h of standard IEC 61215-based damp heat (85 °C, 85% relative humidity) test.

In recent years, photoactive chiral materials are attracting considerable interest owing to relevant applications in optoelectronics as well as high resolution imaging [1]. In these regards, hybrid materials are skyrocketing the field of material science for optoelectronics because they can tune the properties of soft and inorganic assemblies [2]. A recent interesting class of luminescent chiral materials is represented by chiral hybrid perovskites, since they are showing prominent circularly polarized emissions without any need of expensive ferromagnets or extremely low temperatures [3]. Indeed, the chiral source impacts specific non-covalent interactions occurring within the chiral scaffold, which in turn affect the efficiency of the chiral emissions [4,5]. Modern multiscale modeling and simulations nowadays have an unprecedented level of accuracy, enabling an efficient chiral design of luminescent materials. The chiral design concepts of low-dimensional perovskites herein discussed are based on enhanced sampling simulations and TD-DFT calculations [6] from the predicted free-energy basins. This simulation strategy enables to consider a variety of contributions including molecular rotations within the chiral framework, that may affect the generated chiroptical properties.

In the current rush for beating current limits in photovoltaic conversion efficiency (PCE) in highly efficient perovskite solar cells (PSCs), worldwide attempts are mainly focusing on surface defect passivation. As a result, incremental improvement in device open circuit voltage (V_OC) have been obtained, but still far from a breakthrough solution. In this work, we demonstrate an innovative way to minimize V_OC losses by engineering a perovskite photoferroelectric interface. We provide the first proof of concept demonstration – to the best of our knowledge- of a net gain in PCE resulting from inducing an interface ferroelectric polarization. Here, by combing advanced computational studies with interface engineering and in-depth photophysical characterization, we build a photo-ferroelectric interface based on a ferroelectric 2D/3D (band gap=1.59eV)/2D perovskite junction which we integrate in a working device. Upon device polarization, the field generated at the photoferroelectric interface pushes charges far apart, boosting charge collection while preventing their recombination. As a result, the photoferroelectric interface boosts device V_OC to 1.21 V, the highest value obtained so far in literature (considering those devices with PCE>22%), leading to a PCE = 24%. Our results do not only demonstrate a scientific advance demonstrating a fundamental new concept of a working 2D photo-ferroelectric interface but, importantly, they pioneer its application in a working high-efficient solar cell, showing how such photoferroelectric interfaces can have a dramatic effect on device performances, ultimately representing a technological breakthrough, with broader implications even beyond photovoltaics.

Hybrid organic–inorganic perovskites (HOIPs) have emerged as excellent materials for solar cell applications. Indeed, their extreme tunability and facile synthesis have opened the door to many new applications. Chiral HOIPs are attracting great interest as promising frameworks for chiroptoelectronics as well as spintronics applications. The chiroptical properties observed in chiral HOIPs can be explained understanding the chirality transfer from the chiral organic molecules to the achiral inorganic octahedra. A key element of the chirality transfer mechanism involves the distortion of the coordination geometry of the inorganic octahedra induced by the presence of chiral ligands. The specific process through which a chiral bias is generated from a chiral organic ligand to the inorganic scaffold has remained unclear until now.^[1,2] In this study, we propose a tailored simulation workflow based on Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT)^[3] to theoretically explore the chirality transfer mechanism inducing chirality generation and coordination geometry distortion. To this aim, we investigate the chiroptical response of lead- and tin-based 2D chiral perovskites, specifically 2D R- and S-(MBA⁺)₂PbI₄^[4] and R- and S-(MBA⁺)₂SnI₄.^[5] We explore the most impactful factors influencing their Circular Dichroism (CD) signals through ab-initio molecular dynamics simulations and the analysis of the density of electronic states (DOSs). Our findings reveal that the relevant chiroptical features are linked to a chirality transfer event driven by a metal–ligand overlap of electronic levels. This effect is more evident for tin-based chiral perovskites showing higher excitonic coupling. Recent simulations on thermodynamics and kinetics aspects of the early stage of their chiral formation will be also discussed.

Perovskite solar cells (PSCs) are an exciting advancement in energy technology that is both efficient and cost-effective. Cuprous thiocyanate (CuSCN) appears to be a feasible inorganic hole transport material (HTM) for PSCs due to its high hole mobility and strong thermal stability. The use of polar sulfide solvents, particularly diethyl sulfide (DES), during CuSCN film deposition causes issues, affecting the perovskite layer and compromising the PVSK/CuSCN interface contact. The perovskite family is currently investigating potential inorganic HTMs for commercial uses. However, while solution-based film synthesis is less expensive, it introduces DES residue into CuSCN films, resulting in perovskite degradation and device instability. As a consequence, we introduce a novel anti-solvent approach based on ethyl ether (DEE) for recovering DES residue from CuSCN films. This treatment improves film shape and uniformity while reducing flaws, resulting in enhanced PSC performance and stability. This novel method has considerable promise for improving the engineering of CuSCN HTMs and contributing to the specialized commercialization of PSC technology.

Self-assembled Hole Transport Monolayers (HTML) are introduced strategically positioned between the conducting electrodes (ITO) and the active layer in perovskite solar cells (PSC). The primary objective is to elevate device performance by fine-tuning the electronic energy levels of ITO to align with those of the halogenated perovskite (HP) layer1 . This approach aims to enhance charge transfer and energy recovery, thereby optimizing the comprehensive characteristics of PSC. The synthesized organic molecules serving as SAM/HTML possess a distinctive structure: H2PO3-(CH2)2-Cz-R2, where Cz represents carbazole, and R in the 3, 6 position varies as CH3O, NH2, or -CH2NH2. The grafting process onto ITO and on NiO, as well as the determination of SAM orientation, have been meticulously performed to understand both their electronic effects on ITO work function , as a hole-transporting layer (HTL) components and their chemical interactions with the HP. Finally, we thoroughly analyze the SAM structure and PV performances relationship.

Thorough research into the grafting, orientation, and structure of the SAMs were performed using advanced techniques such as IR-Spectroscopy (PM-IRRAS), XPS and UPS. The impact of SAM on the structure of the perovskite MAPbI3 film was investigated through UV-Vis Spectroscopy, X-Ray Diffraction (XRD), and Scanning Electron Microscopy (SEM). This comprehensive analysis explores the influence of SAM on both structure of hybrid perovskite films, photovoltaic performances and stability of perovskite solar cells. Specifically, the study explores the impact of the nature of terminal poles (NH2, CH2NH2 vs. MeO) and the formation of a shared plane with the perovskite layer. Discussions encompass the work function of modified ITO and NiO, the growth of the HP layer, and the orientation of crystallization planes within the perovskite MAPbI3 on HTML/ITO and SAM/NiO/ITO, providing valuable insights into the photovoltaic parameters of the PSC.

The CsPbI3 perovskite halide is the most stable chemical composition for perovskite solar cell applications. However, careful consideration is required for engineering its interfaces to achieve better alignment of energy levels, charge extraction, and power conversion efficiency. Generally, the Spiro-OMeTAD molecule serves as the hole transport layer (HTL) in perovskite solar cells, but its sensitivity to temperature and high-cost pose challenges for commercial applications. Alternatively, poly(3-hexylthiophene) (P3HT) polymer molecule can be utilized as a hole transport layer; however, the interface between P3HT and perovskite often leads to non-radiative recombination. In this study, we introduce a dipole-forming molecule, n-hexyl trimethyl ammonium bromide (HTAB), which forms a 2D layer on the perovskite surface, reduces iodine defects, and improves charge extraction at the interface. As a result, we achieve an impressive Voc of 1.14 V for CsPbI3 and P3HT-based devices, showcasing the effectiveness of our approach interface modification in enhancing device performance.

Colloidal tin-based perovskite nanocrystals have gaining attention for their excellent optoelectronic properties and reduced or negligible toxicity, showing promise for various commercial applications. However, the isolation and purification of the as-synthesized all-inorganic tin-based perovskite nanocrystals remain a challenge, as they rapidly undergo decomposition in common antisolvents and an open atmosphere.[1] Here we mitigate such instabilities and endow strong resistance to antisolvent by introducing an organometallic compound (zinc diethyldithiocarbamate [Zn(DDTC)₂]) during the solution-based synthesis of CsSnI₃ nanocrystals. Thiourea and H₂S are shown to be generated through the thermal-driven conversion of Zn(DDTC)₂ during synthesis, which bind to un-passivated Sn sites on the nanocrystal surface and shields it from irreversible oxidation reactions.[2] The CsSnI₃ nanocrystals resurfaced with thiourea shown great stability after two antisolvent washing cycles using methyl acetate (MeOAc), without any change in morphology, phase, and optical properties. These findings deliver an effective in-situ modification pathway during the synthesis of stable tin-based perovskites and viable platform to explore all-inorganic tin-based nanocrystals optoelectronics.

State-of-the-art display screens are only for information display, while a range of extra different sensors are integrated into the screens for additional functions such as touch control, ambient light sensing, and fingerprint sensing. Future ultra-thin and large screen-to-body ratio screens require the development of novel multifunctional light-emitting diodes (LEDs), which both display information and sense signals - a feature hardly possible for conventional LED technologies. ^[1]

Here, we develop multifunctional displays using highly photo-responsive metal halide perovskite LEDs (PeLEDs) as pixels following our previous publication. ^[2] With efficient defects passivation within perovskite layers, the red emissive PeLEDs shows an external quantum efficiency (EQE) of 10% when working at LED model and a power conversion efficiency (PCE) of 5.34% at photovoltaic model. Due to the strong photo response of the PeLED pixels, the display can be simultaneously used as touch screen, fingerprint sensor, ambient light sensor, and image sensor without integrating any additional sensors. In addition, decent light-to-electricity conversion efficiency of the pixels also enables the display to act as a photovoltaic device which can charge the equipment. ^[3] The multiple-functions of our PeLED pixels can not only simplify the display module structure and realize ultra-thin and light-weight display, but also significantly enhance the user experience by these advanced new applications. As such, our results demonstrate great potential of PeLEDs for a new generation of displays for future electronic devices.

[1] Oh et al., Science 355, 616–619 (2017)

[2] Yuan, Z. et al., Joule 6, 2423-2436, (2022).

[3] Bao, C.^#, Yuan, Z.^#, et al., Nat. Electronics, just accepted (# contribute equally).