Perovskite Photovoltaics Research Articles

Suppressing interfacial nucleation competition through supersaturation regulation for enhanced perovskite film quality and scalability.

The growing interest in cost-effective and high-performing perovskite solar cells (PSCs) has driven extensive research. However, the challenge lies in upscaling PSCs while maintaining high performance. This study focuses on achieving uniform and compact perovskite films without pinholes and interfacial voids during upscaling from small PSCs to large-area modules. Competition in nucleation at concavities with various angles on rough-textured substrates during the gas-pumping drying process, coupled with different drying rates across the expansive film, aggravates these issues. Consequently, substrate roughness notably influences the deposition window of compact large-area perovskite films. We propose a supersaturation regulation approach aimed at achieving compact deposition of high-quality perovskite films over large areas. This involves introducing a rapid drying strategy to induce a high-supersaturation state, thereby equalizing nucleation across diverse concavities. This breakthrough enables the production of perovskite photovoltaics with high efficiencies of 25.58, 21.86, and 20.62% with aperture areas of 0.06, 29, and 1160 square centimeters, respectively.

Scaling-up a Photo-Electrocatalytic Reactor for CO2 Capture and Conversion to Syngas

The most challenging deal we face today is the need to lower greenhouse gas (GHG) emissions and tackle climate change. Though calls to reduce them are growing louder yearly, emissions remain unsustainably high. CO2 is the key contributor to global climate change in the atmosphere. Electrochemical CO2 reduction (EC CO2R) into chemicals or fuels holds great research interest as a promising approach to mitigate CO2 emissions and reach a carbon-neutral future.1 In this regard, an extraordinary effort has been made to discover new efficient and sustainable catalysts at the laboratory level over recent years. High-performance electrocatalysts in aqueous electrolytes often rely on noble metals, which may hinder their industrial applications. Herein, we successfully synthesized core-shell Cu2O/SnO2 nanoparticles2–4 functionalized with a silane group, using a simple and versatile methodology based on a three-step scalable synthesis method involving wet precipitation followed by salinization and, finally, a rhenium-based complex has been assembled by electro-polymerization.5 The carbon paper-supported Cu2O/SnO2-Re electrocatalyst was characterized at 10 cm2 scale achieving a CO:H2 ratio from 3 to 9, and demonstrating an stable syngas production up to 24 hours at -20 mA·cm-2. To translate those developments from the laboratory level to a higher TRL towards the practical application of CO2 capture and utilization6, an additional chamber was added to the system for the continuous CO2 capture and electrochemical conversion, increasing the electrode area from 10 cm2 to 100 cm2. Captured CO2 co-electrolysis to syngas (H2:CO ratio of 5) in one step was demonstrated with a high CO2 conversion at a current up to -2 A, indicating the scale-up potential of this intensified system. The technology is currently under validation in a TRL4 reactor composed of an array of 5 modules (i.e., 4 x 5 cells x 100 cm2) with a total active area of or 0.2m2 for direct CO2 conversion from simulated anthropogenic sources. The design integrates low-cost photovoltaic (PV) cells to provide any required additional bias to drive the reaction, thus, Perovskite PV panels with a cost of up to 5 times lower (10 €/m2) than Si PV cells were used. The TRL5 demonstration of the developed technology will be done with real flue gas emissions the first semester of 2024. Acknowledgements The financial support of the SUNCOCHEM project (Grant Agreement No 862192) of the European Union’s Horizon 2020 Research and Innovation Action programme is acknowledged. References Guzmán, H., Russo, N. & Hernández, S. CO2 valorisation towards alcohols by Cu-based electrocatalysts: challenges and perspectives. Green Chemistry vol. 23 1896–1920 Preprint at https://doi.org/10.1039/d0gc03334k (2021).Cuatto, G. et al. Standardization of Cu2O nanocubes synthesis: Role of precipitation process parameters on physico-chemical and photo-electrocatalytic properties. Chemical Engineering Research and Design 199, 384–398 (2023).Zoli, M., Guzmán, H., Sacco, A., Russo, N. & Hernández, S. Cu2O/SnO2 Heterostructures: Role of the Synthesis Procedure on PEC CO2 Conversion. Materials 16, (2023).Zoli, M. et al. Facile and scalable synthesis of Cu2O-SnO2 catalyst for the photoelectrochemical CO2 conversion. Catal Today 413–415, 113985 (2023).Miró, R. et al. Solar-driven CO2 reduction catalysed by hybrid supramolecular photocathodes and enhanced by ionic liquids. Catal Sci Technol 13, 1708–1717 (2023).Sullivan, I. et al. Coupling electrochemical CO2 conversion with CO2 capture. Nat Catal 4, 952–958 (2021). Figure 1

Self-powered, multi-angle gas flow sensing based on photovoltaics with porous graphite electrodes

A self-powered, multi-attack angle gas/air flow sensor without azimuth directional constraints has been designed and developed in this study. Two essential components, the porous graphite cathode and the perovskite photovoltaics, work synergistically in the device. The gas flow penetrates the bulky porous cathode, causing the pressure differences between the upper and lower sides of the nano/micro sheets, leading to the micro lift-force (Bernoulli theory) or dynamic pressure, consequently breaking or forming the electrically conductive paths among the nano/micro sheets. Therefore, the altered electrical conductivity of the cathode prompts a change in the output photocurrent of the perovskite photovoltaic unit. The thin film photovoltaic device design eliminates the requirement for external power sources, enabling multi-attack angle sensing without any azimuth directional limitations.It's important to highlight the scarcity of micro airfoil structures in the gas flow sensing domain by utilizing the nano/micro graphite sheets as the electrode and the thin film photoelectrical device as the power source, which challenges the conventional design typically based on macro-mechanical theory. It is expected that this study could provide researchers with a fresh and distinct perspective for designing and advancing the next generation of multi-angle gas-flow sensors.

Fusing Science with Industry: Perovskite Photovoltaics Moving Rapidly into Industrialization.

The organic-inorganic lead halide per materials have emerged as highly promising contenders in the field of photovoltaic technology, offering exceptional efficiency and cost-effectiveness. The commercialization of perovskite photovoltaics hinges on successfully transitioning from lab-scale perovskite solar cells to large-scale perovskite solar modules (PSMs). However, the efficiency of PSMs significantly diminishes with increasing device area, impeding commercial viability. Central to achieving high-efficiency PSMs is fabricating uniform functional films and optimizing interfaces to minimize energy loss. This review sheds light on the path toward large-scale PSMs, emphasizing the pivotal role of integrating cutting-edge scientific research with industrial technology. By exploring scalable deposition techniques and optimization strategies, the advancements and challenges in fabricating large-area perovskite films are revealed. Subsequently, the architecture and contact materials of PSMs are delved while addressing pertinent interface issues. Crucially, efficiency loss during scale-up and stability risks encountered by PSMs is analyzed. Furthermore, the advancements in industrial efforts toward perovskite commercialization are highlighted, emphasizing the perspective of PSMs in revolutionizing renewable energy. By highlighting the scientific and technical challenges in developing PSMs, the importance of combining science and industry to drive their industrialization and pave the way for future advancements is stressed.

Stabilization of Organic Cations in Lead Halide Perovskite Solar Cells Using Phosphine Oxides Derivatives.

Preventing ion migration in perovskite photovoltaics is key to achieving stable and efficient devices. The activation energy for ion migration is affected by the chemical environment surrounding the ions. Thus, the migration of organic cations in lead halide perovskites can be mitigated by engineering their local interactions, for example through hydrogen bonding. Ion migration also leads to ionic losses via interfacial reactions. Undesirable reactivities of the organic cations can be eliminated by introducing protecting groups. In this work, we report bis(2-oxo-3-oxazolidinyl) phosphinic chloride (BOP-Cl) as a perovskite ink additive with the following benefits: (1) The phosphoryl and two oxo groups form six-membered intermolecular hydrogen-bonded rings with the formamidinium cation (FA), mitigating ion migrations. (2) The hydrogen bonding reduces the electrophilicity of the ammonium protons by donating electron density, therefore reducing its reactivity with the surface oxygen on the metal oxide. Furthermore, the molecule can react to form a protecting group on the nucleophilic oxygen at the tin oxide transport layer surface through the elimination of chlorine. As a result, we achieve perovskite solar cells with an efficiency of 25.0% and improved MPP stability T93 = 1200 h at 40-45 °C compared to a control device (T86 = 550 h). In addition, we show a negative correlation between the strength of hydrogen bonding of different phosphine oxide derivatives to the organic cations and the degree of metastable behavior (e.g., initial burn-in) of the device.

From Chalcogen Bonding to S-π Interactions in Hybrid Perovskite Photovoltaics.

The stability of hybrid organic-inorganic halide perovskite semiconductors remains a significant obstacle to their application in photovoltaics. To this end, the use of low-dimensional (LD) perovskites, which incorporate hydrophobic organic moieties, provides an effective strategy to improve their stability, yet often at the expense of their performance. To address this limitation, supramolecular engineering of noncovalent interactions between organic and inorganic components has shown potential by relying on hydrogen bonding and conventional van der Waals interactions. Here, the capacity to access novel LDperovskite structures that uniquely assemble through unorthodox S-mediated interactions is explored by incorporating benzothiadiazole-based moieties. The formation of S-mediated LD structures is demonstrated, including one-dimensional (1D) and layered two-dimensional (2D) perovskite phases assembled via chalcogen bonding and S-π interactions. This involved a combination of techniques, such as single crystal and thin film X-ray diffraction, as well as solid-state NMR spectroscopy, complemented by molecular dynamics simulations, density functional theory calculations, and optoelectronic characterization, revealing superior conductivities of S-mediated LD perovskites. The resulting materials are applied in n-i-p and p-i-n perovskite solar cells, demonstrating enhancements in performance and operational stability that reveal a versatile supramolecular strategy in photovoltaics.

Ionic liquid engineering enables 1D/3D perovskite photovoltaics with > 25 % efficiency: A real-time study exploring formation mechanism of 1D perovskites

The advancements in low-dimensional/three-dimensional (LD/3D) perovskite devices represent a promising approach to enhancing both the efficiency and stability of of perovskite solar cells (PSCs). However, while significant efforts have been dedicated to understanding the role of already formed low-dimensional perovskites in passivating defects, refining the work function, little attention has been given to the crystallization process of LD perovskites, particularly when induced by ionic liquids (ILs) as green and stable additive. In this work, the formation process of IL Tetrabutylammonium Thiocyanate (TBASCN)-induced 1D perovskite onto the 3D perovskite under varying annealing conditions were explored by in-situ Grazing-Incidence Wide-Angle X-ray Scattering (GIWAXS) technology, providing a comprehensive investigation into the distinct impacts of 1D perovskite formed under diverse annealing processes on device performance. Owing to the robust interaction and favorable binding energy between the IL TBASCN and perovskite components, coupled with the low formation energy of 1D perovskites, 1D perovskites exhibit rapid formation on the surface of 3D perovskites and display markedly distinct crystallization processes under distinguished annealing conditions. Achieving full crystallization of 1D perovskites necessitates optimal temperature of 100 °C and adequate duration of 100 s. Once fully crystallized, the highly crystalline 1D perovskites and anions SCN- present in ILs can synergistically passivate defects in 3D perovskites, mitigate ion migration and impeding moisture infiltration. Benefiting from the optimized formation process of 1D perovskites, the champion device achieves a power conversion efficiencie (PCE) of 25.18 % and retains 91.0 % of its initial efficiency after 2000 h under RH=40 %. Our research provides new insights for optimizing the formation process of LD perovskites induced by different materials and their application in high-performance LD/3D PSCs.

Large Orientation Angle Buried Substrate Enables Efficient Flexible Perovskite Solar Cells and Modules.

Flexible perovskite solar cells (f-PSCs) have emerged as potential candidates for specific mechanical applications owing to their high foldability, efficiency, and portability. However, the power conversion efficiency (PCE) of f-PSC remains limited by the inferior contact between perovskite and flexible buried substrate. Here, an asymmetric π-extended self-assembled monolayer (SAM) (4-(9H-dibenzo[a,c]carbazol-9-yl)butyl)phosphonic acid (A-4PADCB) is reported as a buried substrate for efficient inverted f-PSCs. Employing this design strategy, A-4PADCB exhibits a significant orientation angle away from the surface normal, homogenizing the distribution of contact potentials. This enhancement improves the SAM/perovskite interface quality, controlling the growth of favorable perovskite films with low defect density and slight tensile stress. Integration of A-4PADCB into small-area f-PSCs and large-area flexible perovskite solar modules with an aperture area of 20.84cm2 achieves impressive PCEs of up to 25.05% and 20.64% (certified 19.51%), respectively. Moreover, these optimized A-4PADCB-based f-PSCs possess enhanced light, thermal, and mechanical stability. This research paves a promising avenue toward the design of SAM-buried substrates with a large orientation angle, regulating perovskite growth, and promoting the commercialization of large-area flexible perovskite photovoltaics.

Elucidating roles of fulleropyrrolidine-based materials as extraordinary electron transporters for boosting efficiency of perovskite photovoltaics

To achieve an ideal electron transfer layer (ETL) for perovskite solar cell (PSC), effective compounds were developed based on fullerene C60 functionalized with a pyrrolidine ring (fulleropyrrolidine), to which a cyanoethyl group, a thiophene ring, and four DNA bases were attached. Density functional theory (DFT) calculations were employed to study structural, electronic, optical, and electron mobility features of these materials. To more precisely determine the HOMO and LUMO energy levels of all samples, the NBO calculations were accomplished at PBE0-D3/6-31G(d,p) theoretical level. The LUMO levels of all ETL samples could be aligned with the conduction band of perovskite CsFAMAPbIBr via their coupling within fabricated PSCs, enabling easy electron injection from CsFAMAPbIBr to the Ag electrode. All functionalized fullerene C60–based ETLs exhibited very high electron mobilities in the range of 0.744–1.598 cm2V−1s−1 which were significantly greater than 1.461 × 10−5 cm2V−1s−1 for pure C60 as the reference. High fill factors (FFs), power conversion efficiencies (PCEs), and open circuit voltages (VOC) were measured for PSC devices with C60–based ETLs, varying within the ranges of 0.892–0.897, 22.489–23.984 %, and 1.111–1.179 V, respectively, indicating they could yield excellent photovoltaic parameters.

Effects of Ligand Chemistry on Ion Transport in 2D Hybrid Organic–Inorganic Perovskites

Abstract2D hybrid organic–inorganic perovskites are potentially promising materials as passivation layers that can enhance the efficiency and stability of perovskite photovoltaics. The ability to suppress ion transport is proposed as a stabilization mechanism, yet an effective characterization of relevant modes of halide diffusion in 2D perovskites is nascent. In light of this knowledge gap, molecular dynamics simulations with enhanced sampling and experimental validation to systematically characterize how ligand chemistry in seven (R‐NH3)2PbI4 systems impacts halide diffusion, particularly in the out‐of‐plane direction is combined. It is found that increasing stiffness and length of ligands generally inhibits ion transport, while increasing ligand polarization generally enhances it. Structural and energetic analyses of the migration pathways provide quantitative explanations for these trends, which reflect aspects of the disorder of the organic layer. Overall, this mechanistic analysis greatly enhances the current understanding of halide migration in 2D hybrid organic–inorganic perovskites and yields insights that can inform the design of future passivation materials.

Sustainability pathways for perovskite photovoltaics.

Solar energy is the fastest-growing source of electricity generation globally. As deployment increases, photovoltaic (PV) panels need to be produced sustainably. Therefore, the resource utilization rate and the rate at which those resources become available in the environment must be in equilibrium while maintaining the well-being of people and nature. Metal halide perovskite (MHP) semiconductors could revolutionize PV technology due to high efficiency, readily available/accessible materials and low-cost production. Here we outline how MHP-PV panels could scale a sustainable supply chain while appreciably contributing to a global renewable energy transition. We evaluate the critical material concerns, embodied energy, carbon impacts and circular supply chain processes of MHP-PVs. The research community is in an influential position to prioritize research efforts in reliability, recycling and remanufacturing to make MHP-PVs one of the most sustainable energy sources on the market.

23.81%-Efficiency Flexible Inverted Perovskite Solar Cells with Enhanced Stability and Flexibility via a Lewis Base Passivation.

Lewis base molecules bind the undercoordinated lead atoms at interfaces and grain boundaries, leading to the high efficiency and stability of flexible perovskite solar cells (PSCs). We demonstrated a highly efficient, stable, and flexible PSC via interface passivation using a Lewis base of tri(o-tolyl)phosphine (TTP). It not only induced an intimate interface contact and a complete deposition of the perovskite thin layers on hole transport layers (HTLs) but also led to a better perovskite with a raised crystallinity, fewer defects, and a better morphology, including fewer gullies, high uniformity, and low roughness. Furthermore, the TTP treatments induced a good alignment of energy levels among the perovskites, HTLs, and C60. The resultant flexible inverted PSCs exhibited a high power conversion efficiency (PCE) of 23.81%, which is one of the highest PCEs among these flexible inverted PSCs. Moreover, the optimized flexible PSCs exhibited high storage stability, superior operation stability, and enhanced mechanical flexibility. This study presents an effective method to substantially raise the PCE, stability, and mechanical flexibility of the flexible inverted perovskite photovoltaics.

Optimized SnO2 preparation and coherent interlayers for enhanced charge dynamics and efficient perovskite photovoltaics

The dense, uniform and conformal electron transport layers (ETLs) will largely promote charge separation and extraction. Here, the mixed acid (hydrochloric acid and nitric acid) was used to regulate preparation process and enhance utilization of materials, and the colloids of tin oxide (SnO2) nanocrystals were prepared through hydrothermal process. The complete dissolution of Sn source can increase purity, produce homogeneous precursor, reduce grain sizes and improve film-coverage. As confirmed, a coherent interlayer at the SnO2 ETLs/perovskite interfaces will be achieved by coupling a Cl-bonded SnO2 film with a Cl-containing perovskite precursor. This thin coherent interlayer will largely reduce interface traps, enhance rapid carrier extraction, and impede charge recombination. The uniform polymer phase of (PEO)120-(PPO)30 will be used to passivate traps at the grain boundaries of perovskite films and further improve the photovoltaic performance. The maximum energy conversion efficiency (23.17%, a VOC of 1.153 V, a JSC of 24.75 mA cm−2 and a FF of 0.812) of perovskite solar cells was achieved. The charge separation, extraction, and recombination kinetics (charge dynamic process) was determined by the related characterization techniques. The functionalized SnO2-ETLs and formed coherent interlayer will provide a simple strategy to effectively decrease interface traps, enhance charge extraction, and facilitate development of perovskite solar cells.

Nanometer Control of Ruddlesden-Popper Interlayers by Thermal Evaporation for Efficient Perovskite Photovoltaics.

Solution-processed Ruddlesden-Popper (RP) interlayers in lead halide perovskite solar cells (PSCs) present processing challenges due to fast film formation and uncontrolled growth of phases and layer thickness at interfaces. In this work, an alternative, solvent-free, thermal co-evaporation process is developed to deposit RP interlayers. The method provides precise control on interlayer thickness and enables understanding its role on charge-carrier extraction. Studying RP film growth reveals the development of heterointerfaces when deposited on three-dimensional (3D) perovskite layers. This allows a large thickness window with an optimum between 20 nm and 40 nm to improve the optoelectronic properties of the underlying 3D perovskite. Solar cells using evaporated interlayers achieve power conversion efficiency of 21.6%, compared to 19.6% for untreated devices, driven by improvements in the open-circuit voltage and fill factor. This work sheds light on the importance of phase and thickness control of passivation layers, which ultimately determine the solar cell performance in state-of-the-art PSCs.

Lead-Chelating Intermediate for Air-Processed Phase-Pure FAPbI3 Perovskite Solar Cells.

Formamidinium-lead triiodide (FAPbI3) perovskite holds promise as a prime candidate in the realm of perovskite photovoltaics. However, the photo-active α-FAPbI3 phase, existing as a metastable state, is observable solely at elevated temperatures and is susceptible to degradation into the δ-phase in ambient air. Therefore, the attainment of phase-stable α-FAPbI3 in ambient conditions has become a crucial objective in perovskite research. Here, we proposed an efficient conversion process of PbI2 into the α-FAPbI3 perovskites in ambient air. This conversion was facilitated by the introduction of chelating molecules, which interacted with PbI2 to form an intermediate phase. Due to the reduced formation barrier resulting from the altered reaction pathway, this stable intermediate phase transitioned directly into α-FAPbI3 upon the deposition of the organic cation solution, effectively bypassing the formation of δ-FAPbI3. Consequently, the ambient-fabricated FAPbI3 perovskite solar cells (PSCs) exhibited an outstanding power conversion efficiency of 25.08 %, along with a high open-circuit voltage of 1.19 V. Furthermore, the unencapsulated devices demonstrated remarkable environmental stability. Notably, this innovative approach promises broad applicability across various chelating molecules, opening new avenues for further progress in the ambient air fabrication of FAPbI3 PSCs.

Lead‐Chelating Intermediate for Air‐Processed Phase‐Pure FAPbI3 Perovskite Solar Cells

AbstractFormamidinium‐lead triiodide (FAPbI3) perovskite holds promise as a prime candidate in the realm of perovskite photovoltaics. However, the photo‐active α‐FAPbI3 phase, existing as a metastable state, is observable solely at elevated temperatures and is susceptible to degradation into the δ‐phase in ambient air. Therefore, the attainment of phase‐stable α‐FAPbI3 in ambient conditions has become a crucial objective in perovskite research. Here, we proposed an efficient conversion process of PbI2 into the α‐FAPbI3 perovskites in ambient air. This conversion was facilitated by the introduction of chelating molecules, which interacted with PbI2 to form an intermediate phase. Due to the reduced formation barrier resulting from the altered reaction pathway, this stable intermediate phase transitioned directly into α‐FAPbI3 upon the deposition of the organic cation solution, effectively bypassing the formation of δ‐FAPbI3. Consequently, the ambient‐fabricated FAPbI3 perovskite solar cells (PSCs) exhibited an outstanding power conversion efficiency of 25.08 %, along with a high open‐circuit voltage of 1.19 V. Furthermore, the unencapsulated devices demonstrated remarkable environmental stability. Notably, this innovative approach promises broad applicability across various chelating molecules, opening new avenues for further progress in the ambient air fabrication of FAPbI3 PSCs.

Silicon‐Inspired Analysis of Interfacial Recombination in Perovskite Photovoltaics

AbstractPerovskite solar cells have reached an impressive certified efficiency of 26.1%, with a considerable fraction of the remaining losses attributed to carrier recombination at perovskite interfaces. This work demonstrates how time‐resolved photoluminescence spectroscopy (TRPL) can be utilized to locate and quantify remaining recombination losses in perovskite solar cells, analogous to methods established to improve silicon solar cell passivation and contact layers. It is shown how TRPL analysis can be extended to determine the bulk and surface lifetimes, surface recombination velocity, the recombination parameter, J0, and the implied open‐circuit voltage (iVoc) of any perovskite device configuration. This framework is used to compare 18 carrier‐selective and passivating contacts commonly used or emerging for perovskite photovoltaics. Furthermore, the iVoc values calculated from the TRPL‐based framework are directly compared to those calculated from photoluminescence quantum yields and the measured solar cell Voc. This simple technique serves as a practical guide for screening and selecting multifunctional, passivating perovskite contact layers. As with silicon solar cells, most of the material and interface analysis can be done without fabricating full devices or measuring efficiency. These purely optical measurements are even preferable when studying bulk and interfacial passivation approaches, since they remove complicating effects from poor carrier extraction.

Ultrastable and efficient slight-interlayer-displacement 2D Dion-Jacobson perovskite solar cells

Stability has been a long-standing concern for solution-processed perovskite photovoltaics and their practical applications. However, stable perovskite materials for photovoltaic remain insufficient to date. Here we demonstrate a series of ultrastable Dion−Jacobson (DJ) perovskites (1,4-cyclohexanedimethanammonium)(methylammonium)n−1PbnI3n+1 (n ≥ 1) for photovoltaic applications. The scalable technology by blade-coated solar cells for the designed DJ perovskites (nominal n = 5) achieves a maximum stabilized power conversion efficiency (PCE) of 19.11% under an environmental atmosphere. Un-encapsulated cells by blade-coated technology retain 92% of their initial efficiencies for over 4000 hours under ~90% relative humidity (RH) aging conditions. More importantly, these cells also exhibit remarkable thermal (85 °C) and operational stability, which shows negligible efficiency loss after exceeding 5000-hour heat treatment or after operation at maximum power point (MPP) exceeding 6000 hours at 45 °C under a 100 mW cm−2 continuous light illumination.

Blade-Coating (100)-Oriented α-FAPbI3 Perovskite Films via Crystal Surface Energy Regulation for Efficient and Stable Inverted Perovskite Photovoltaics.

Photoactive black-phase formamidinium lead triiodide (α-FAPbI3) perovskite has dominated the prevailing high-performance perovskite solar cells (PSCs), normally for those spin-coated, conventional n-i-p structured devices. Unfortunately, α-FAPbI3 has not been made full use of its advantages in inverted p-i-n structured PSCs fabricated via blade-coating techniques owing to uncontrollable crystallization kinetics and complicated phase evolution of FAPbI3 perovskites during film formation. Herein, a customized crystal surface energy regulation strategy has been innovatively developed by incorporating 0.5 mol % of N-aminoethylpiperazine hydroiodide (NAPI) additive into α-FAPbI3 crystal-derived perovskite ink, which enabled the formation of highly-oriented α-FAPbI3 films. We deciphered the phase transformation mechanisms and crystallization kinetics of blade-coated α-FAPbI3 perovskite films via combining a series of in-situ characterizations and theoretical calculations. Interestingly, the strong chemical interactions between the NAPI and inorganic Pb-I framework help to reduce the surface energy of (100) crystal plane by 42 %, retard the crystallization rate and lower the formation energy of α-FAPbI3. Benefited from multifaceted advantages of promoted charge extraction and suppressed non-radiative recombination, the resultant blade-coated inverted PSCs based on (100)-oriented α-FAPbI3 perovskite films realized promising efficiencies up to 24.16 % (~26.5 % higher than that of the randomly-oriented counterparts), accompanied by improved operational stability. This result represented one of the best performances reported to date for FAPbI3-based inverted PSCs fabricated via scalable deposition methods.

Yttrium Metal–Organic Framework Nanocrystals for Two‐Step Deposited Perovskite Photovoltaics with Enhanced UV‐light Durability

AbstractMetal–organic frameworks (MOFs), renowned for their porous and tunable functionalities, hold significant potential for enhancing perovskite photovoltaic. However, the influence of MOF, particularly those with balanced cations in the pores, on the conversion of bottom‐layer PbI2 and the distribution of MOFs within perovskite remains underexplored. Herein, a newly synthesized Yttrium (Y)‐MOF material is introduced, featuring dimethylamine (DMA) as balanced cations within its pores and strong absorption in UV regime, to modify perovskite films. Y‐MOF, rich in oxygen and nitrogen sites, and featuring DMA within its pores, can passivate uncoordinated Pb2+ in perovskite. Scanning electron microscopy (SEM) and grazing incidence wide‐angle X‐ray scattering (GIWAXS) analysis of the top and bottom surfaces for pristine and Y‐MOF‐assisted perovskite samples reveal that the presence of PbI2 in the Y‐MOF‐assisted perovskite films is negligible. In situ UV–vis analyses demonstrate that the incorporation of Y‐MOF decelerates the crystallization kinetics of perovskite, facilitating the development of larger perovskite grains. Moreover, GIWAXS experiments conducted at different angles reveal the predominant bottom distribution of Y‐MOF within the perovskite, which effectively mitigates the impact of ultraviolet light on the perovskite. Consequently, the Y‐MOF‐assisted devices to achieve an efficiency of 24.05% with improved stability especially the UV‐light stability.