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The emergence of the artificial intelligence urgently requires novel devices to handle massive data and bionic simulations. As one of new generation memory devices, memristor has great potential in information storage and brain‐like learning due to its merits, such as low energy consumption, high speed and etc. In addition, the randomness for the generation and breakage of the conducting filaments in the memristor can generate the true random numbers and realize the image encryption. In this work, the ITO/Cs2AgBiBr6/Al based devices exhibit prominent resistance variation characteristics and long‐term environmental stability (≥6 months). Additionally, the flexible PET/ITO/Cs2AgBiBr6/Al devices are assembled and measured resistance variation properties, which are adopt to realize the cryptographic processing of image information. The synaptic plasticity of the memristor is also verified, including paired pulse facilitation and spiking timing‐dependent plasticity. Finally, nociceptive responses are also simulated with the memristor via imposing different voltage. Nociceptive characteristics including “threshold,” “relaxation,” and “sensitization” have been successfully determined. The work provides possibility for lead‐free flexible perovskite memristors in information security and biomimicry. [ABSTRACT FROM AUTHOR]

An original molecular imprinting photoelectrochemical (PEC) sensor for sarcosine detection based on stable lead-free inorganic halide double perovskite Cs2AgBiBr6 is proposed. Cs2AgBiBr6 as a lead-free halide perovskite material possesses several positive optoelectronic properties for PEC analysis, such as long-lived component to the charge-carrier lifetime, and strong absorption of visible light. At the same time, two-dimensional materials also offer excellent electronic and mechanical properties; thus, Bi2O2S was used and combined with Cs2AgBiBr6 to provide a stable and large photocurrent, which also benefits from the stability of perovskite Cs2AgBiBr6. Based on this novel PEC assay, the detection range for sarcosine was between 0.005 and 5000 ng/mL with a low detection limit of 0.002 ng/mL. This work also improved the adhibition of metal halide perovskite in analytical chemistry field, providing a novel way for other small molecule detection. [ABSTRACT FROM AUTHOR]

Lead-free double perovskites are a newly developed category of non-toxic material with impressive photoelectric properties and excellent inherent environmental stability. This study explores the design and performance optimization of lead-free double perovskite/c-Si tandem devices (TDs). Two top cells (TCs) made of Cs 4 CuSb 2 Cl 12 (bandgap of 1.6 eV) and Cs 2 AgBiBr 6 (bandgap of 2.05 eV) absorber materials and the bottom cell (BC) of c-Si (bandgap of 1.12 eV), have been utilized for designing two TDs. To design an efficient TD's structure, TC and BC were first individually simulated and calibrated against the findings derived from the reported experimental data. The absorber's thickness of TC reaches the current matching, when the current it generates under AM 1.5G spectrum matches the BC's current under a filtered spectrum (generated through TC). At current matching condition, the optimized values of thickness of Cs 4 CuSb 2 Cl 12 and Cs 2 AgBiBr 6 layers are 0.418 and 1.29 μm, respectively. The lead-free Cs 4 CuSb 2 Cl 12 / c - Si and Cs 2 AgBiBr 6 / c - Si TDs exhibit a PCE (power conversion efficiency) value of 34.67% ( V OC = 1.82 V, J SC = 20.75 mA / cm 2 , FF = 88.31%) and 36.88% ( V OC = 2.16 V, J SC = 21.105 mA / cm 2 , FF = 79.68%), respectively. Performance parameters of TDs obtained from this work are comparable to the results of reported experiments and simulations. Analysis of this study reveals that enhancing PCE of double-perovskite TC is essential to promise the TD's benefits. The results reported demonstrate that lead-free and stable double perovskite materials can act as an essential absorber in sub-cells for highly efficient, commercially viable, non-toxic and eco-friendly tandem photovoltaic technologies. [ABSTRACT FROM AUTHOR]

As numerous studies on highly efficient perovskite solar cells have been conducted on lead‐based light absorbers, such as MAPbI3 and FAPbI3, increasing concerns are rising regarding toxicity and stability issues. One of the most prominent and promising lead‐free alternatives is the double‐perovskite Cs2AgBiBr6, which is well‐suited for multi‐junction solar cells considering its relatively large indirect bandgap of around 1.95–2.05 eV. Despite distinctive reports on its performance under ambient conditions, the demonstrated stability has not yet been conclusively clarified. Within this study, the degradation behavior of Cs2AgBiBr6 single crystals is investigated under different ambient environments, such as AM1.5g solar irradiation, aquatic conditions, and humidity. The corresponding samples are analyzed by using Raman, UV–vis, energy‐dispersive X‐Ray, and micro‐photoluminescence spectroscopies together with X‐Ray diffraction. High intrinsic stability of Cs2AgBiBr6 in ambient conditions and severe degradation in aquatic conditions are observed. Furthermore, surface morphology alterations are found during the simulated solar irradiation indicating photo‐accelerated degradation behavior. In the results of this study, it is clearly implied that intense research efforts need to be put into sealing the Cs2AgBiBr6 layer in solar cells with the goal of protecting it from humidity and water intrusion simultaneously, therefore avoiding photo‐accelerated degradation. [ABSTRACT FROM AUTHOR]

Lead-free double perovskites (DPs) have received a lot of attention owing to their good stability and environmental friendliness. They have been widely used in the field of optoelectronics because of their high quantum efficiency and long carrier migration distance. However, the application of lead-free DPs in ultrafast photonics is rarely explored. Cs2AgBiBr6, a typical lead-free double perovskite, has advantages such as toxicity free of Pb, high stability, and strong nonlinear absorption, showing great potential application in ultrafast photonics. However, to date, there is no reported research on the application of Cs2AgBiBr6 in ultrafast optical devices. Herein, we prepared Cs2AgBiBr6 nanocrystals, tested their ultrafast nonlinear absorption properties, and further prepared them as a saturable absorber (SA) to achieve stable mode-locking pulses in Er-doped fiber lasers. The results show that it has a low saturation intensity (0.75 MW/cm2), resulting in a low starting threshold power (50 mW) for mode-locking. The obtained pulsed fiber laser shows a pulse width as narrow as 452 fs. In addition, the Cs2AgBiBr6 SA has unique advantages in long-term stability and it was found that this Cs2AgBiBr6 SA can still work well after 10 months. In general, our results prove that Cs2AgBiBr6 is an excellent nonlinear optical material and has good application potential in ultrafast photonics. [ABSTRACT FROM AUTHOR]

Reversible optical property changes in lead‐free perovskites have recently received great interest due to their potential applications in smart windows, sensors, data encryption, and various on‐demand devices. However, it is challenging to achieve remarkable color changes in their thin films. Here, methylamine gas (CH3NH2, MA0) induced switchable optical bleaching of bismuth (Bi)‐based perovskite films is demonstrated for the first time. By exposure to an MA0 atmosphere, the color of Cs2AgBiBr6 (CABB) films changes from yellow to transparent, and the color of Cs3Bi2I9 (CBI) films changes from dark red to transparent. More interestingly, the underlying reason is found to be the interactions between MA0 and Bi3+ with the formation of an amorphous liquefied transparent intermediate phase, which is different from that of lead‐based perovskite systems. Moreover, the generality of this approach is demonstrated with other amine gases, including ethylamine (C2H5NH2, EA0) and butylamine (CH3(CH2)3NH2, BA0), and another compound, Cs3Sb2I9, by observing a similar reversible optical bleaching phenomenon. The potential for the application of CABB and CBI films in switchable smart windows is investigated. This study provides valuable insights into the interactions between amine gases and lead‐free perovskites, opening up new possibilities for high‐efficiency optoelectronic and stimuli‐responsive applications of these emerging Bi‐based materials. [ABSTRACT FROM AUTHOR]

As numerous studies on highly efficient perovskite solar cells have been conducted on lead‐based light absorbers, such as MAPbI3 and FAPbI3, increasing concerns are rising regarding toxicity and stability issues. One of the most prominent and promising lead‐free alternatives is the double‐perovskite Cs2AgBiBr6, which is well‐suited for multi‐junction solar cells considering its relatively large indirect bandgap of around 1.95–2.05 eV. Despite distinctive reports on its performance under ambient conditions, the demonstrated stability has not yet been conclusively clarified. Within this study, the degradation behavior of Cs2AgBiBr6 single crystals is investigated under different ambient environments, such as AM1.5g solar irradiation, aquatic conditions, and humidity. The corresponding samples are analyzed by using Raman, UV–vis, energy‐dispersive X‐Ray, and micro‐photoluminescence spectroscopies together with X‐Ray diffraction. High intrinsic stability of Cs2AgBiBr6 in ambient conditions and severe degradation in aquatic conditions are observed. Furthermore, surface morphology alterations are found during the simulated solar irradiation indicating photo‐accelerated degradation behavior. In the results of this study, it is clearly implied that intense research efforts need to be put into sealing the Cs2AgBiBr6 layer in solar cells with the goal of protecting it from humidity and water intrusion simultaneously, therefore avoiding photo‐accelerated degradation.

This study introduces an innovative approach involving the synthesis of lead-free halide double perovskite (LFHDP) solar cell Cs2AgBiBr6 and that with the doping of trans-polyacetylene (t-PA) via the sol–gel method. Through X-ray diffraction (XRD) analysis, we confirm the cubic structure and, in addition, an observable growth in grain size attributed to t-PA doping. A comprehensive exploration of optical parameters, including band gap, refractive index, electronegativity, extinction coefficient, and dielectric constant was conducted through UV–Vis spectrophotometry. The pristine Cs2AgBiBr6 exhibited a band gap energy (Eg) of 1.9 eV, while with t-PA doping the Eg decreased to 1.84 eV, indicating a notable enhancement in light absorption. The calculated optical electronegativity is 0.49 which suggests a shift towards a more covalent nature. The J-V curve shows parameters for pristine thin film as Jsc of 5.13 mA/cm2, Voc of 0.92 V, FF of 0.69, and the efficiency of 3.29 %. On the other hand, the t-PA doped thin film exhibits improvement of the parameters which are Jsc of 5.7 mA/cm2, Voc of 0.929 V, and FF of 0.75, leading to a significantly elevated efficiency of 3.98 %. This enhanced efficiency is 20.97 % higher than that of the pure Cs2AgBiBr6, clearly showing an uplifted performance. In addition to the experiment, computational method based on finite difference time domain technique was used to check the stability of the material. The study shows the mechanical and dynamical stability of the Cs2AgBiBr6.

As lead halide perovskites face toxicity and stability issues, research on the eco-friendly double perovskite Cs2AgBiBr6 has become increasingly popular. While the majority of research on this Cs2AgBiBr6 perovskite material has been concentrated on photovoltaic performance and promising applications, its enduring stability and degradation process have received far less attention. This article presents a thorough numerical analysis of an eco-friendly Cs2AgBiBr6 double perovskite solar cell (PSC) model with a standard n-i-p architecture FTO/C60/Cs2AgBiBr6/MoS2/Pt. In-depth research has been done on several device characteristics, including the defect density and the thickness of the electron transport layer (ETL), hole transport layer (HTL), and absorber layer, and back-contact electrode work function. Through parameter optimization, we were able to achieve an open-circuit voltage (Voc) of 0.84 V, short-circuit current density (Jsc) of 32.28 mA/cm2, and fill factor (FF) of 85.77% with power conversion efficiency (PCE) of 23.49% under AM1.5G illumination, which is significantly greater than the highest stated values identified in the literature. [ABSTRACT FROM AUTHOR]

Low‐cost and efficient large‐scale triboelectric nanogenerator (TENG) is considered as the new scheme for distributed mechanical conversion or renewable energy utilization. An extremely popular all‐inorganic lead‐free double perovskite Cs2AgBiBr6 (CABB) has emerged as extraordinary potential material in triboelectric semiconductors' substitution, overcoming high‐impedance limitations associated with organic‐polymer‐insulator based materials. In this study, assembled by the certified available positive frictional material CABB, TENG with sandwiched structure of ITO/compact‐TiO2/mesoporous‐TiO2/CABB – the poly‐tetra‐fluoroethylene/Al exhibits appropriate performance on environmental stability and output capacity for which structure can impede charges decay. Fabrication process comparison shows that as an inexpensive large‐scale functional films preparation method, sprayed CABB TENG with brilliant relative dielectric constant and work function difference possess more distinguished output characteristics. This is confirmed by higher open‐circuit voltage of 105 V, larger short‐current density of 2.45 mA m−2 at 0.25 Hz motion parameter, and more abundant output power density of 0.76 W m−2 under 10 Hz. Further study confirms that both higher frequency and larger contact‐area are conducive to total output power, while terminal charging speed is inversely or positively proportional with capacitance or mechanical frequency. Final physical display effect of sprayed CABB TENG lights up at least 53 commercial yellow‐LEDs, holding decent energy conversion ability. [ABSTRACT FROM AUTHOR]

Herein, Cs2AgBiBr6 double perovskite films, which is considered one of the alternative materials to organic–inorganic Pb‐based perovskites in terms of toxicity and stability, are fabricated by gas‐quenching approach in ambient environment for the first time. Moreover, the study examines the effect of gas flowing rate on the solvent evaporation rate, crystallinity, morphology, and optical properties of the perovskite. The results indicate that the duration of color change from transparent to shiny yellow during gas quenching of Cs2AgBiBr6 films is influenced by the gas flowing rate, and this parameter has a notable impact on the properties of the films. In addition, incorporation of the gas‐quenched Cs2AgBiBr6 thin films in perovskite solar cells leads to 1.47% power conversion efficiency with open‐circuit voltage of 1.04 V, short‐circuit current density of 2.11 mA cm−2, and fill factor of 67.4%. Overall, this study provides a new approach to fabricate Cs2AgBiBr6 thin films in ambient atmosphere for potential optoelectronic applications. [ABSTRACT FROM AUTHOR]

Abstract Reversible optical property changes in lead‐free perovskites have recently received great interest due to their potential applications in smart windows, sensors, data encryption, and various on‐demand devices. However, it is challenging to achieve remarkable color changes in their thin films. Here, methylamine gas (CH3NH2, MA0) induced switchable optical bleaching of bismuth (Bi)‐based perovskite films is demonstrated for the first time. By exposure to an MA0 atmosphere, the color of Cs2AgBiBr6 (CABB) films changes from yellow to transparent, and the color of Cs3Bi2I9 (CBI) films changes from dark red to transparent. More interestingly, the underlying reason is found to be the interactions between MA0 and Bi3+ with the formation of an amorphous liquefied transparent intermediate phase, which is different from that of lead‐based perovskite systems. Moreover, the generality of this approach is demonstrated with other amine gases, including ethylamine (C2H5NH2, EA0) and butylamine (CH3(CH2)3NH2, BA0), and another compound, Cs3Sb2I9, by observing a similar reversible optical bleaching phenomenon. The potential for the application of CABB and CBI films in switchable smart windows is investigated. This study provides valuable insights into the interactions between amine gases and lead‐free perovskites, opening up new possibilities for high‐efficiency optoelectronic and stimuli‐responsive applications of these emerging Bi‐based materials.

With the advantage of high bandwidth, low power consumption, and low crosstalk from optical signal stimulation, optoelectronic synapses are attracting more and more attention. Herein, a self‐powered two‐terminal optoelectronic synapse based on a lead‐free Cs2AgBiBr6 perovskite/P(VDF‐TrFE)/pentacene heterostructure is designed, which shows bidirectional responses to optical stimuli with different wavelengths (λ = 445 nm/660 nm). This feature enables the device to emulate both excitatory and inhibitory synaptic behaviors in a fully optical pathway. Besides optical stimulus, humidity is used as an additional stimulus to modulate the synaptic performance of the device under 445 nm illumination. The device is successfully applied to stimulate the behavior of the weather tree forecast and visual learning and forgetting processes under different mood states via humidity regulation. [ABSTRACT FROM AUTHOR]

Exploring highly efficient and stable halide perovskite‐based materials for photocatalytic CO2 reduction is a great challenge due to their poor intrinsic instability. Coincidentally, mesoporous molecular sieves have received tremendous attention as adsorbents, catalysts, and catalyst carriers. Herein, lead‐free double perovskite of Cs2AgBiBr6 (CABB) nanocrystals are grown in situ in MCM‐48 mesoporous molecular sieve for photocatalytic CO2 reduction. A remarkable performance is achieved by the CABB@MCM‐48 composite, which far exceeds that of pristine CABB. The mechanism of the photocatalytic CO2 reduction reaction is systematically investigated by the combination of in situ diffuse reflectance infrared Fourier transform spectra and density functional theory calculations. The result indicates that the molecular sieve can not only enhance the adsorption of CO2 molecules, but also promote the CO2 activation by reducing the energy barriers. This study provides some new insights into the design of excellent perovskite/molecular sieve‐based catalysts for solar fuel applications. [ABSTRACT FROM AUTHOR]

Conventional lead halide Perovskite Solar Cells (PSC) have toxicity and stability issues. Therefore it is crucial to look for lead-free inorganic perovskite material, such as La2NiMnO6, RbGeI3, CsGeI3, Cs2AgBiBr6 and others. There has been much work in the area of PSC using Cs2AgBiBr6 as an absorber, However, due to some critical issues of Cs2AgBiBr6, such as the film's broad bandgap which limits its capacity to absorb light, leading to corresponding PSC being typically restricted to around 4% efficiency. In this work, a lead-free PSC with Cs2AgBiBr6 as the absorber has been engineered to resolve the issues by considering the experimental works in the literature to increase efficiency to 6.3% from a maximum 4.48% as reported in the literature. The output response of both design approaches, as well as the potentiality of future designs, are investigated in terms of output parameters, i.e., Open-Circuit Voltage (VOC), Short-circuit Current density (JSC), Fill Factor (FF), and Power Conversion Efficiency (PCE). Besides, this work also focuses on eliminating Sulphur from ETLs by working on several sulphides and oxide-based Electron Transport Layers (ETLs). Several solar cell device structures have been analyzed for their numerical simulation with sulphide ETLs such as ZnS, WS2, CdS, CdZnS and oxide ETLs such as TiO2, ZnO, WO3, IGZO. To progress towards eco-friendly PSCs, alternatives to sulphide, several transparent oxide alternatives (TiO2, ZnO, WO3, IGZO) have been considered as ETLs. These ETLs have been further doped with Mg to enhance the performance parameters. Mg-doped based ETLs additionally behaving as Hole-blocking layers (HBLs) in corresponding PSCs leads to comparatively significantly better performance in a number of aspects, including VOC (1.21 V), PCE (5.74%), JSC, and FF. The solar cell design has been optimized for high performance through various techniques such as varying ETL and absorber thickness, interface defects variation, series/shunt resistance, band to band recombination, and bandgap grading through doping. Also an effective electric field (Eeff) that depicts the conduction's impact has been calculated. Best performing device among different designs among PSCs with sulphide and oxide-based ETLs has been ZnS/Cs2AgBiBr6/Cu2O (PCE-6.3%) and Mg-doped (20%) ZnO/Cs2AgBiBr6/Cu2O (PCE-5.74%). These results may help researchers in their efforts to find the best-suited materials for the design of high-performance PSCs in the future. [ABSTRACT FROM AUTHOR]

[Display omitted] Halide perovskite solar cells (PSCs) have become a representative of novel photovoltaic power generation technologies. However, the toxicity and instability problems of lead (Pb) halide perovskite constitute a major obstacle to their commercialization. In recent years, a nontoxic, highly stable lead-free double perovskite Cs 2 AgBiBr 6 cells emerged as a promising alternative to Pb-based PSCs, which is quickly becoming one of the hottest topics in photovoltaics. This review identifies the major challenges faced by Cs 2 AgBiBr 6 PSCs and provides a comprehensive review on corresponding solution strategies for the community. These results will contribute insights and theoretical guidance to the subsequent development of Cs 2 AgBiBr 6 PSCs. Finally, we propose research perspectives toward efficient, eco-friendly, and practical photovoltaic Cs 2 AgBiBr 6 PSCs. [ABSTRACT FROM AUTHOR]

Elpasolite Cs2AgBiBr6 also known as double perovskite has been touted in recent years as a promising alternative to the lead‐based perovskite for light harvesting. Its structure and properties mainly stem from the replacement of Pb2+ cation with a pair of aliovalent silver (Ag+) and bismuth (Bi3+) cations. Although the elpasolite Cs2AgBiBr6 exhibits improved stability, its photophysical properties and device performance are inferior to those of the Pb‐based perovskites. To date, numerous efforts have been geared toward the development of efficient Cs2AgBiBr6 solar cells. However, the indirect, wide bandgap and high exciton binding energy of Cs2AgBiBr6 have limited such efforts. This has been attributed to its low (zero) electronic dimensionality (0D), formation of small polaronic states, and interfacial imperfections with charge transporting layers. In this review, the different aspects of the elpasolite Cs2AgBiBr6 in relation to compositional and interlayer interactions in solar cell are discussed, and its suitability for photovoltaic application is assessed, accompanied by potential measures to further advance its performance. An alternate application of Cs2AgBiBr6 in photocatalysis, which takes advantage of its less toxicity and better stability, is also discussed. [ABSTRACT FROM AUTHOR]

The advancement of lead-free double perovskite materials has drawn great interest thanks to their reduced toxicity, and superior stability. In this regard, Cs2AgBiBr6 perovskites have appeared as prospective materials for photovoltaic (PV) applications. In this work, we present design and numerical simulations, using SCAPS-1D device simulator, of Cs2AgBiBr6-based double perovskite solar cell (PSC). The initial calibrated cell is based on an experimental study in which the Cs2AgBiBr6 layer has the lowest bandgap (Eg = 1.64 eV) using hydrogenation treatment reported to date. The initial cell (whose structure is ITO/SnO2/Cs2AgBiBr6/Spiro-OMeTAD/Au) achieved a record efficiency of 6.58%. The various parameters that significantly affect cell performance are determined and thoroughly analyzed. It was found that the conduction band offset between the electron transport layer (ETL) and the Cs2AgBiBr6 layer is the most critical factor that affects the power conversion efficiency (PCE), in addition to the thickness of the absorber film. Upon engineering these important technological parameters, by proposing a double ETL SnO2/ZnO1-xSx structure with tuned absorber thickness, the PCE can be boosted to 14.23%. [ABSTRACT FROM AUTHOR]

[Display omitted] All-inorganic lead-free halide double perovskites have emerged as rising star photocatalysts to substitute the toxic lead-based hailed perovskites (LHPs) owing to their unique photophysical properties. Nevertheless, their photocatalytic activities toward CO 2 reduction are still far from comparable with the LHPs, associated with severe charge recombination and sluggish surface catalytic reaction. Herein, a delicate 0D/2D heterojunction of Cs 2 AgBiBr 6 /Bi 2 WO 6 (CABB/BWO) was assembled by in-situ growing cubic CABB nanocrystals on the flat surface of BWO nanosheets via a facile hot-injection method. Density functional theory (DFT) calculations disclose that the work function and Fermi level difference between CABB and BWO give rise to charge redistribution at the interface upon the formation of the heterojunction, creating an internal electric field (IEF). Upon light irradiation, the IEF enables the photogenerated electron transfer from BWO to CABB via direct Z-scheme electron transfer mode with striking spatial charge separation as verified by in-situ X-ray photoelectron (XPS) and electron spin resonance (ESR) spectra. Consequently, the CABB/BWO heterojunction realizes 7-fold higher photocatalytic activity than pristine CABB with significant electron consumption rate of 87.66 µmol g-1h−1 under simulated solar light (AM 1.5G). [ABSTRACT FROM AUTHOR]

Cs2AgBiBr6 is an encouraging example of perovskites which shows potential toward the development of more stable and nontoxic photoactive materials. However, relative to its necessarily large optical thickness, the material has substantially deficient electron diffusion lengths, which limit its photovoltaic efficiency. Herein, this problem is solved by designing a double‐sided semitransparent architecture for a Cs2AgBiBr6‐based photovoltaic material. In this case, the bifacial design deliberately creates an imbalance between the electron and hole densities, resulting in asymmetric lengths of carrier conduction near their respective transporting layers. Coupled optoelectronic simulations suggest that the use of the bifacial architecture results in an improvement of around 34% in the efficiency, from 3.47% to 4.64%, compared to the standard configuration. This method is effective to improve electron conduction in Cs2AgBiBr6, which is typically severe compared to its hole conduction. Finally, the strength of the correlation between the power conversion efficiency of the bifacial architecture and the diffusion length, asymmetric ratio of electron and hole conduction, and light albedo factor are explored. The results highlight some ways to improve the photovoltaic efficiency of Cs2AgBiBr6 above 8%, for instance, through tuning the surface recombination and band alignment between Cs2AgBiBr6 and the hole‐transporting layer. [ABSTRACT FROM AUTHOR]

[Display omitted] Lead-free inorganic Cs 2 AgBiBr 6 double perovskites have emerged as promising materials in perovskite solar cells (PSCs) to tackle the inferior stability and toxicity issues of organic–inorganic hybrid PSCs. However, the power conversion efficiencies (PCEs) of Cs 2 AgBiBr 6 solar cells are remarkably restricted by the intrinsic and extrinsic defects of Cs 2 AgBiBr 6 films. More specifically, the fast crystallization process in the formation of Cs 2 AgBiBr 6 films strongly prevents the homogeneous growth of perovskite crystals, leading to inferior Cs 2 AgBiBr 6 film quality. This work introduces a facile strategy to retard the crystallization of Cs 2 AgBiBr 6 perovskites by introducing Lewis base additives into the precursor solution. The incorporation of a strongly coordinated thiourea additive with a sulfur donor leads to the generation of a Lewis acid base adduct, which retards the crystallization process for Cs 2 AgBiBr 6 crystals, improves the quality of the Cs 2 AgBiBr 6 film, decreases the defect density and inhibits charge carrier recombination. After optimization, the cell delivers a superior PCE of 3.07%, surpassing that reported for most Cs 2 AgBiBr 6 -based solar cells in the literature, and exhibits outstanding stability with a PCE retention rate of 95% after 20 days of storage in air. This work provides an effective strategy for further improvements in the performance of inorganic lead-free Cs 2 AgBiBr 6 -based photovoltaic cells. [ABSTRACT FROM AUTHOR]

Lead‐free double perovskite Cs2AgBiBr6 has gained increasing attention recently. However, the power conversion efficiency (PCE) of Cs2AgBiBr6 perovskite solar cells (PSCs) is still low compared with their lead‐based counterparts. Here, by using photoluminescence (PL), time‐resolved photoluminescence (TRPL), and ultrafast transient absorption (TA) measurements, the unbalance between the electron and hole in diffusion and transfer, which limits the performance of the Cs2AgBiBr6 PSCs, was further revealed. Considering this issue, a strategy of using the mesoporous TiO2 electron transport layer (ETL) to construct a bulk heterojunction in Cs2AgBiBr6 PSCs was proposed. Consequently, the PCE had improved by over 24% comparing with that only used compact TiO2 ETL. Moreover, based on mesoporous TiO2, the unencapsulated Cs2AgBiBr6 PSCs maintained 90% of their initial performance after approximately 1200 h of storage in a desiccator (humidity ~30%). This work gives further understanding of Cs2AgBiBr6 perovskite and demonstrates that a proper design of balancing the electron and hole diffusion can improve device performance. [ABSTRACT FROM AUTHOR]

The ferroelectric perovskite material Cs 2 AgBiBr 6 has received much attention because of its low poisonous nature and environmental stability. In this paper, we prepared high-quality Cs 2 AgBiBr 6 thin films for self-powered photodetectors using a low-pressure-assisted method, investigated their optical, electrical, and pyroelectric properties, and characterized the film morphology and crystallization. The device modulates the photoelectric process without an external power supply, and has a maximum switching ratio of 1.72 × 106, a response rate of 0.158 A/W, a specific detectivity of 1.39 × 1011 Jones, an external quantum efficiency of 52.8 %, and a fast response time of 15.4/16.8 μs when irradiated with 532 nm light, which is much better than that of previous self-powered devices with the same material on/off ratio and specific detectivity. It is worth mentioning that the pyroelectric effect was observed in the infrared band. In addition, the devices exhibited high stability to water and oxygen in an air environment (25 °C, 60 % humidity), retaining more than 95 % of the initial performance after one month of placement. Our study demonstrates that the lead-free perovskite Cs 2 AgBiBr 6 is a promising and environmentally friendly alternative for the preparation of highly stable self-powered photodetectors and is also of great research value in the field of pyroelectric detection. • The pyroelectric effect of the Cs 2 AgBiBr 6 thin-film device was observed in the infrared band. This paper explains the effect in terms of light-induced changes in the temperature gradient. • The Cs 2 AgBiBr 6 thin films are prepared by a low-pressure-assisted method and the devices have good morphology and properties. • The device modulates the photoelectric process without an external power supply and has a maximum switching ratio of 1.72 × 106 and a response time of 15.4/16.8 μs. The device retains more than 95 % of the initial performance after one month of placement in an air environment (25 °C, 60 % humidity). [ABSTRACT FROM AUTHOR]

The amount and type of defects in Cs2AgBiBr6 are controlled by varying the Ag/Bi ratio of the precursor solutions in two different synthesis routes, that is, slow solution cooling crystallization and fast microwave‐assisted hydrothermal synthesis. The correlation between the Ag/Bi ratio in the precursor solution and defect formation in the crystals is studied by band broadening analysis in Raman spectroscopy, the estimated Urbach energy in UV–vis spectroscopy, and thermogravimetric analysis. Ag‐rich precursors are found to prevent the formation of the secondary‐phase Cs3Bi2Br9, but at the same time induced the formation of Br vacancies and antisite defects. Time‐resolved photoluminescence measurements reveal that the formation of beneficial defects such as Br vacancies causes to trap the charge carriers, thus avoiding the recombination of charge carriers and leading to a longer carrier lifetime. Herein, the findings provide a guidance to decrease the defect densities and can be applied to the fabrication of Pb‐free solar cells based on Cs2AgBiBr6.

Sb‐substituted Cs2AgBiBr6 single crystals and powders are synthesized by various wet‐chemical routes as well as by solvent‐free mechanochemical synthesis. Phase purity and resulting optical properties of differently synthesized Sb‐substituted Cs2AgBiBr6 absorbers are investigated and compared. X‐ray diffraction confirms that Sb substitution results in an apparent single‐phase formation with a unit cell shrinkage up to a certain substitution limit, which varies depending on the synthesis routes. Questions about the phase identification determined by X‐ray diffraction are raised and thoroughly investigated by Raman spectroscopy. UV–vis spectroscopy reveals that Sb3+ substitution induces a reduction in the optical bandgap of Cs2AgBiBr6, whereas octahedral factor calculations provide that SbBr6 octahedra can be hardly stable in a Cs2AgBiBr6 double perovskite. The experimental results of the occurrence and evolution of Raman bands and theoretical calculations of the structural stability of SbBr6 octahedra in Cs2AgBiBr6 unambiguously raise doubts about the Sb‐substitution feasibility in Cs2AgBiBr6, and a general substitution strategy in Cs2AgBiBr6 is discussed. [ABSTRACT FROM AUTHOR]

Exploring efficient and stable halide perovskite-based photocatalysts is a great challenge due to the balance between the photocatalytic performance, toxicity, and intrinsic chemical instability of the materials. Here, the environmentally friendly lead-free perovskite Cs 2 AgBiBr 6 confined in the mesoporous TiO 2 crystal matrix has been designed to enhance the charge carrier extraction and utilization for efficient photocatalytic rifampicin degradation. The as-prepared Cs 2 AgBiBr 6 /TiO 2 catalyst was stable in air for over 500 days. An S-scheme heterojunction was formed between the (004) plane of Cs 2 AgBiBr 6 and the (101) plane of TiO 2 through the Bi-O-Br bonds. The built-in electric field at the interface efficiently promoted the photoinduced charge separation and carrier extraction. The Cs 2 AgBiBr 6 /TiO 2 -200 showed a 92.83% degradation efficiency of rifampicin within 80 min under simulated sunlight illumination (AM 1.5G 100 mW cm -2 ). This work offers an effective way for the construction of halide perovskite-based photocatalysts with high photocatalytic performance, good stability, and low toxicity simultaneously.

Broadband photodetectors covering ultraviolet (UV) to near-infrared (NIR) wavelengths play an essential role in communications, imaging, and biosensing. Developing a single photodetector with a broadband optical response operating at room temperature can significantly reduce the complexity and cost of receiver systems for multispectral applications. In this work, utilizing the porous structure characteristics of Cs 2 AgBiBr 6 :Sn thin films, a self-powered detector with broad spectral response (UV-vis-NIR) was achieved by constructing an effective Cs 2 AgBiBr 6 :Sn/PDPP3T heterojunction. This photodetector possesses a broad response spectrum from 350 to 950 nm with an average detection rate exceeding 10 11 Jones and maintains excellent photoelectric performance over two months. Sn 2+ doping effectively reduces the bandgap of Cs 2 AgBiBr 6 , enhancing its near-infrared absorption and optimizing energy level alignment with conjugated polymer (diketopyrrolopyrrole-terthiophene, PDPP3T). More importantly, the porous structure derived from Sn doping significantly improves carrier extraction and transport under a near-infrared light response at the heterojunction interface. Utilizing its broad spectral response characteristics in the UV-vis-NIR range, a novel information transfer and encryption system employing full optical modulation has been realized within a single perovskite photodetector. This work provides a new approach to fabricating lead-free double perovskite broadband photodetectors with potential applications in photonic devices.

Lead-free halide double perovskite (HDP) Cs 2 AgBiBr 6 has set a benchmark for research in HDP photoelectric applications due to its attractive optoelectronic properties. However, its narrow absorption range is a key limitation of this material. Herein, a novel dopant, palladium (Pd), is doped into Cs 2 AgBiBr 6 and significantly extends the absorption to ≈1400 nm. Pd 2+ ions are partially doped in the host lattice, most probably replacing Ag atoms and introducing a sub-bandgap state within the host bandgap, as indicated by the combination of spectroscopical measurements and theoretical calculations. Importantly, this sub-bandgap state extends the photoresponse of Cs 2 AgBiBr 6 up to the NIR-II region of 1300 nm, setting a new record for HDPs. This work demonstrates a novel and efficient dopant for HDPs and highlights the effectiveness of employing a sub-bandgap to broaden the absorption of HDPs, shedding new light on tailoring large bandgap HDPs for NIR optoelectronic applications., (© 2024 The Author(s). Small published by Wiley‐VCH GmbH.)

A neuromorphic visual system integrating optoelectronic synapses to perform the in‐sensor computing is triggering a revolution due to the reduction of latency and energy consumption. Here it is demonstrated that the dwell time of photon‐generated carriers in the space‐charge region can be effectively extended by embedding a potential well on the shoulder of Schottky energy barrier. It permits the nonlinear interaction of photocurrents stimulated by spatiotemporal optical signals, which is necessary for in‐sensor reservoir computing (RC). The machine vision with the sensor reservoir constituted by designed self‐powered Au/P(VDF‐TrFE)/Cs2AgBiBr6/ITO devices is competent for both static and dynamic vision tasks. It shows an accuracy of 99.97% for face classification and 100% for dynamic vehicle flow recognition. The in‐sensor RC system takes advantage of near‐zero energy consumption in the reservoir, resulting in decades‐time lower training costs than a conventional neural network. This work paves the way for ultralow‐power machine vision using photonic devices. [ABSTRACT FROM AUTHOR]

All‐inorganic lead‐free Cs2AgBiBr6 double perovskite solar cells (PSCs) have attracted growing attention owing to their eco‐friendly features and robust intrinsic stability. However, arising from the rapid crystal growth, the poor film quality always leads to substantial non‐radiative recombination and inferior performance improvement. Herein, high‐efficiency and stable Cs2AgBiBr6 PSCs are obtained by introducing a functional polymethyl methacrylate (PMMA) layer at the perovskite surface to avoid direct contact between carbon and the underlying charge transfer layer, as well as to passivate the defects. When assembling into solar cells, the non‐radiative charge recombination is suppressed and the interfacial charge extraction is accelerated. As a result, the carbon‐electrode‐based Cs2AgBiBr6 PSC yields an enhanced efficiency of 2.25% with a high open‐circuit voltage of 1.18 V. Moreover, the unencapsulated device exhibits superior long‐term stability owing to the protection of the PMMA layer from corrosion by the extraneous water and oxygen, retaining nearly 100% of the initial efficiency after storage in 25 °C, with 5% relative humidity (RH) for 80 days and high temperature of 85 °C, and 0% RH for 60 days, respectively. A simple method of polymer passivation for enhancing the performance and stability of Pb‐free Cs2AgBiBr6 PSCs is provided. [ABSTRACT FROM AUTHOR]

Artificial synapses combined with artificial neural networks can develop next-generation computer framework. This computer framework has the characteristics of low energy consumption, high density, self-learning and self-storage. We designed and prepared artificial synapse based on all-inorganic perovskite Cs 2 AgBiBr 6 (CABB). This work studies the synaptic excitatory behavior of CABB synapses in neurology. By applying electrical spikes, it can exhibit excitatory behaviors similar to biological synapses. On this basis, using its synaptic excitement, we simulated some conceived functions of human-like artificial intelligence, including pain simulation, Pavlov learning, letter learning and number recognition. After testing, it can be found that CABB synapse can complete these tasks. In order to realize number recognition, we designed a multi-layer neural network according to the weight update method of CABB synapse. It shows a recognition accuracy of 91.57 %. [Display omitted] • Cs 2 AgBiBr 6 thin films were synthesized by chemical solution depositions. • The all-inorganic perovskite Cs 2 AgBiBr 6 memristor was studied in artificial synapses. • It can realize functions such as pain simulation, Pavlov learning, and letter learning. • The neural network composed of Cs 2 AgBiBr 6 synapses can realize 91.57 % recognition accuracy. [ABSTRACT FROM AUTHOR]

Lead-free halide double perovskites (LFHDPs) based on Cs 2 AgBiBr 6 provide a promising replacement for conventional lead-based LBPs, offering significant benefits in terms of non-toxicity and chemical stability. Nevertheless, the efficiency of Cs 2 AgBiBr 6 solar cells is restricted due to their significant bandgap (E g). The proposed solution involves optimizing the optical and photovoltaic properties of Cs 2 AgBiBr 6 through graphdiyne (GD) doping. The synthesized Cs 2 Ag 0.95 GD 0.05 BiBr 6 is extensively characterized by means of X-ray diffraction (XRD), solar simulator studies, and UV–vis spectroscopy. XRD analysis reveals peak position shifts, indicating changes in the crystal structure caused by GD doping. Optical examination indicates a drop in E g , this results in enhanced light absorption in the visible region. The increased performance of the Cs 2 Ag 0.95 GD 0.05 BiBr 6 solar cell is demonstrated by its higher fill factor (FF), open-circuit voltage (V oc), and short-circuit current (J sc), which are measured at 0.91 V, 5.58 mA-cm−2, and 0.75, respectively. As a result, the power conversion efficiency (PCE) increases to 3.74 % from 3.37 %. Our research not only tackles film formation issues but also develops stable Cs 2 Ag 0.95 GD 0.05 BiBr 6 as a high-performance material for solar applications. All in all, our effort promotes solar technology that is environmentally benign. This work develops stable Cs 2 Ag 0.95 GD 0.05 BiBr 6 as a high-performance substance that aids in overcoming film forming challenges in solar applications. Overall, our work advances ecologically friendly solar technology. • Pure and Graphdiyen doped Cs 2 AgBiBr 6 films have been prepared by sol-gel spin coating technique. • XRD confirmed the doping and cubic phase of both films. • Graphdiyne doped Cs 2 AgBiBr 6 contains large grain size, small E g and high refractive index. • Graphdiyne-Cs 2 AgBiBr 6 cell exhibits a high J sc (5.58 mA-cm−2), V oc (0.91 V), and efficiency (3.74 %). [ABSTRACT FROM AUTHOR]

Abstract A neuromorphic visual system integrating optoelectronic synapses to perform the in‐sensor computing is triggering a revolution due to the reduction of latency and energy consumption. Here it is demonstrated that the dwell time of photon‐generated carriers in the space‐charge region can be effectively extended by embedding a potential well on the shoulder of Schottky energy barrier. It permits the nonlinear interaction of photocurrents stimulated by spatiotemporal optical signals, which is necessary for in‐sensor reservoir computing (RC). The machine vision with the sensor reservoir constituted by designed self‐powered Au/P(VDF‐TrFE)/Cs2AgBiBr6/ITO devices is competent for both static and dynamic vision tasks. It shows an accuracy of 99.97% for face classification and 100% for dynamic vehicle flow recognition. The in‐sensor RC system takes advantage of near‐zero energy consumption in the reservoir, resulting in decades‐time lower training costs than a conventional neural network. This work paves the way for ultralow‐power machine vision using photonic devices.

This work has developed a theoretical model to investigate the mechanisms of nonlinear steady-state photocurrent versus dose rate characteristics in Cs 2 AgBiBr 6 -based X-ray detectors. The photocurrent analysis on Cs 2 AgBiBr 6 -based X-ray detector shows that there is a photocurrent gain, primarily due to the presence of dark current. Charge injection from metal contacts is the primary source of dark current in Cs 2 AgBiBr 6. The accumulation of X-ray induced ions near the electrodes elevates the metal/perovskite interface electric field, and hence increases the charge injection with the X-ray dose. The Schottky barrier height for charge injection is found to be dependent on the X-ray dose as well. Therefore, the variation of dark current under X-ray exposures are mainly responsible for the non-linear steady-state photocurrent. The comparison of the model with the experimental results reveals the accumulated ion concentrations and effective barrier heights. • An analytical photocurrent model has been developed. • There is a photocurrent gain due to dark current in Cs 2 AgBiBr 6 X-ray detector. • The dark current is primarily caused by charge injection from the metal contacts. • Interface electric field and effective barrier height modify charge injection. [ABSTRACT FROM AUTHOR]

• Through X-ray diffraction (XRD) analysis, cubic structure of Cs 2 AgBiBr 6 is confirmed. • The pristine Cs 2 AgBiBr 6 exhibited a band gap energy (E g) of 1.9 eV, while with t-PA doping the E g decreased to 1.84 eV. • The calculated optical electronegativity is 0.49 which suggests a shift towards a more covalent nature. • The J-V curve of t-PA doped thin film exhibits improvement in efficiency of 3.98%. This study introduces an innovative approach involving the synthesis of lead-free halide double perovskite (LFHDP) solar cell Cs 2 AgBiBr 6 and that with the doping of trans -polyacetylene (t-PA) via the sol–gel method. Through X-ray diffraction (XRD) analysis, we confirm the cubic structure and, in addition, an observable growth in grain size attributed to t-PA doping. A comprehensive exploration of optical parameters, including band gap, refractive index, electronegativity, extinction coefficient, and dielectric constant was conducted through UV–Vis spectrophotometry. The pristine Cs 2 AgBiBr 6 exhibited a band gap energy (E g) of 1.9 eV, while with t-PA doping the E g decreased to 1.84 eV, indicating a notable enhancement in light absorption. The calculated optical electronegativity is 0.49 which suggests a shift towards a more covalent nature. The J-V curve shows parameters for pristine thin film as J sc of 5.13 mA/cm2, V oc of 0.92 V, FF of 0.69, and the efficiency of 3.29 %. On the other hand, the t-PA doped thin film exhibits improvement of the parameters which are J sc of 5.7 mA/cm2, V oc of 0.929 V, and FF of 0.75, leading to a significantly elevated efficiency of 3.98 %. This enhanced efficiency is 20.97 % higher than that of the pure Cs 2 AgBiBr 6 , clearly showing an uplifted performance. In addition to the experiment, computational method based on finite difference time domain technique was used to check the stability of the material. The study shows the mechanical and dynamical stability of the Cs 2 AgBiBr 6. [ABSTRACT FROM AUTHOR]

Tandem solar cells have a wider photon absorption range, allowing them to provide better efficiency than single-junction SC. The upper cell absorbs high-energy photons, while the lower cell absorbs low-energy filtered photons. However, in order to obtain affordable, efficient, and long-lasting SC, the absorber layers of the t o p and b o t t o m cells must be integrated with an adequate bandgap. This research suggests tandem perovskite solar cells as upper band active materials in this setting. The Si homojunction solar cell's performance was improved by investigating the thicknesses of the p − t y p e and n − t y p e layers, doping concentrations, and defect densities. The thickness variation of the p e r o v s k i t e solar cell (100 − 400 n m) is then optimized. To precisely replicate the tandem devices, the estimated spectra of the perovskite SC are optically filtered onto the lower cells. Current matching was achieved by adjusting the thickness of the p e r o v s k i t e sub-cell with different bottom layer thicknesses, and the optimized efficiency of 36.26 % for the p e r o v s k i t e / S i tandem device was shown. The discoveries will open the door for the upcoming creation of h i g h − e f f i c i e n c y , low-energy solar cells. • On the basis of SCAPS-1D software, the optical characteristics are investigated in order to correlate the novel eco-friendly tandem solar cell. • Use the results obtained for the elaboration of these samples and to make an optimized solar cell (work in progress). • This paper encourages the fabrication of future flexible solar cells. [ABSTRACT FROM AUTHOR]

The advancement of lead-free double perovskite materials has drawn great interest thanks to their reduced toxicity, and superior stability. In this regard, Cs2AgBiBr6 perovskites have appeared as prospective materials for photovoltaic (PV) applications. In this work, we present design and numerical simulations, using SCAPS-1D device simulator, of Cs2AgBiBr6-based double perovskite solar cell (PSC). The initial calibrated cell is based on an experimental study in which the Cs2AgBiBr6 layer has the lowest bandgap (Eg = 1.64 eV) using hydrogenation treatment reported to date. The initial cell (whose structure is ITO/SnO2/Cs2AgBiBr6/Spiro-OMeTAD/Au) achieved a record efficiency of 6.58%. The various parameters that significantly affect cell performance are determined and thoroughly analyzed. It was found that the conduction band offset between the electron transport layer (ETL) and the Cs2AgBiBr6 layer is the most critical factor that affects the power conversion efficiency (PCE), in addition to the thickness of the absorber film. Upon engineering these important technological parameters, by proposing a double ETL SnO2/ZnO1-xSx structure with tuned absorber thickness, the PCE can be boosted to 14.23%.

Background: Halide double perovskite Cs2AgBiBr6 shows promising potential applications in next-generation photovoltaic devices. The strain engineering strategy has been proven as a reliable method to improve its performance. The fundamental physical tensor of elastic constants Cij has not been accurately measured yet, due to the limited size of samples. Objective: The aim of this work is to measure its full elastic tensor Cij using various techniques. Methods: We utilized nanoindentation and contact resonance atomic force microscopy (CR-AFM) techniques to measure the elastic modulus on an as-grown facet, which is along the [111] direction. Then, the inelastic X-ray scattering (IXS) approach and density functional theory were introduced to obtain the accurate full elastic constant Cij of single crystal Cs2AgBiBr6. Results: The full elastic constants were measured as C11 = 44.52 GPa, C12 = 17.63 GPa and C44 = 8.56 GPa. The results for the modulus along the [111] direction reveal that nanoindentation and CR-AFM are sufficiently reliable for quantitative measurements of small single crystals Cs2AgBiBr6. Conclusions: The results provide guidelines for strain engineering in the photovoltaic applications using Cs2AgBiBr6 and for elastic property measurements in nanomaterials. [ABSTRACT FROM AUTHOR]

Background: Halide double perovskite Cs2AgBiBr6 shows promising potential applications in next-generation photovoltaic devices. The strain engineering strategy has been proven as a reliable method to improve its performance. The fundamental physical tensor of elastic constants Cij has not been accurately measured yet, due to the limited size of samples. Objective: The aim of this work is to measure its full elastic tensor Cij using various techniques. Methods: We utilized nanoindentation and contact resonance atomic force microscopy (CR-AFM) techniques to measure the elastic modulus on an as-grown facet, which is along the [111] direction. Then, the inelastic X-ray scattering (IXS) approach and density functional theory were introduced to obtain the accurate full elastic constant Cij of single crystal Cs2AgBiBr6. Results: The full elastic constants were measured as C11 = 44.52 GPa, C12 = 17.63 GPa and C44 = 8.56 GPa. The results for the modulus along the [111] direction reveal that nanoindentation and CR-AFM are sufficiently reliable for quantitative measurements of small single crystals Cs2AgBiBr6. Conclusions: The results provide guidelines for strain engineering in the photovoltaic applications using Cs2AgBiBr6 and for elastic property measurements in nanomaterials. [ABSTRACT FROM AUTHOR]

Lead-free double perovskite halides are emerging optoelectronic materials that are alternatives to lead-based perovskite halides. Recently, single-crystalline double perovskite halides were synthesized, and their intriguing functional properties were demonstrated. Despite such pioneering works, lead-free double perovskite halides with better crystallinity are still in demand for applications to novel optoelectronic devices. Here, we realized highly crystalline Cs2AgBiBr6 single crystals with a well-defined atomic ordering on the microscopic scale. We avoided the formation of Ag vacancies and the subsequent secondary Cs3Bi2Br9 by manipulating the initial chemical environments in hydrothermal synthesis. The suppression of Ag vacancies allows us to reduce the trap density in the as-grown crystals and to enhance the carrier mobility further. Our design strategy is applicable for fabricating other lead-free halide materials with high crystallinity.

Halide perovskites have garnered significant attention for their unique optoelectronic properties in solar-to-fuel conversions. However, the efficiency of halide perovskites in the field of photocatalytic CO 2 reduction is largely limited by serious charge recombination and a lack of efficient active sites. In this work, a rubidium (Rb) doped Cs 2 AgBiBr 6 (Rb:CABB) hierarchical microsphere is developed for photocatalytic CO 2 reduction. Experimental and theoretical analysis discloses that partially substituting Rb + for Ag + can effectively modulate the electronic structure of CABB, favoring charge separation and making adjacent Bi atoms an electron-rich active site. Further investigations indicated that Rb doping also reduces the energy barriers of the rate-determining step in CO 2 reduction. As a result, Rb:CABB demonstrated an enhanced CO yield compared to its undoped counterpart. This work presents a promising approach to optimizing the electronic structures of photocatalysts and paving a new way for exploring halide perovskites for photocatalytic CO 2 reduction., (© 2024 Wiley‐VCH GmbH.)

Double perovskite, Cs2AgBiBr6, is introduced as a lead-free perovskite solar cell. Device modeling of Cs2AgBiBr6 (DP) was accomplished to obtain the optimum parameters using the Solar Cell Capacitance Simulator (SCAPS). Two devices with two different hole transport layers (HTLs) were investigated, including P3HT and Cu2O. For both devices with different HTLs, an optimal thicknesses of 1200 nm and defect densities of 1.0 × 1014 cm−3 for DP layer were attained. For both HTLs, conduction band offset, CBO, is − 0.21 eV and valence band offset, VBO, is + 0.16 eV. For shallow acceptor doping concentration of P3HT and Cu2O, the values of 5.0 × 10 19 and 5.0 × 10 17 cm - 3 were obtained, respectively. As far as the shallow donor density of electron transport layers (ETLs) is concerned, for both cases, the optimum value of 5.0 × 1019 cm−3 were achieved. For capture cross section, σ n , p , in absorber layer for both HTLs, the optimal value at σ n , p of 10 - 20 cm 2 for N t , D P ( defect density of DP) is 10 16 cm - 3 , at σ n , p of 10 - 19 cm 2 for N t , D P is 10 15 cm - 3 , at σ n , p of 10 - 18 cm 2 for N t , D P is 10 14 cm - 3 , at σ n , p of 10 - 17 cm 2 for N t , D P is 10 13 cm - 3 , and at σ n , p of 10 - 16 cm 2 for N t , D P is 10 12 cm - 3 . For P3HT device, the interface defect density of P3HT/Cs2AgBiBr6 is occurred at 1.0 × 1014 cm−2, and for Cs2AgBiBr6/SnO2 is happened at 1.0 × 109 cm−2. For Cu2O device, the interface defect density of Cu2O/Cs2AgBiBr6 is befallen at 1.0 × 1013 cm−2, and for Cs2AgBiBr6/SnO2 is happened at 1.0 × 1010 cm−2. As for radiative recombination, for P3HT device, the optimal value is happened at 2.3 × 10−13 cm3/s, however, for Cu2O device is occurred at 2.3 × 10−12 cm3/s. Finally, for P3HT device, a maximum power conversion efficiency, PCE, of 11.69% (open-circuit voltage, Voc, of 2.02 V, short-circuit current density, Jsc, of 6.39 mA/cm2, and fill-factor, FF, of 0.90 (90%)) were achieved, and for Cu2O device, a PCE of 11.32% (Voc of 1.97 V, Jsc of 6.39 mA/cm2, and FF of 0.895 (89.5%)) were attained. This is the highest efficiency for Cs2AgBiBr6 double perovskite solar cell which was achieved till now. Finally, our results are providing towards fabricating a lead-free and inorganic solar cell. [ABSTRACT FROM AUTHOR]

A lead-free all-inorganic Cs 2 AgBiBr 6 double perovskite nanocrystals photocatalyst exhibits excellent ability to eliminate NO gas under visible light irradiation. [Display omitted] • Lead-free Cs 2 AgBiBr 6 double perovskite nanocrystals were first applied to NO photocatalytic field. • Cs 2 AgBiBr 6 NCs show excellent stability toward air and heat. • The removal efficiency of NO can reach up to 97.22% under visible light. • The photocatalytic mechanism of Cs 2 AgBiBr 6 NCs was proposed. Lead halide perovskite nanocrystals (NCs) have been recognized as a rather competitive candidates for potential advanced optoelectronic applications. But the toxicity of lead and the intrinsic instability are the key concerns for their large-scale commercialization. For addressing these tricky issues, we synthesized lead-free all-inorganic Cs 2 AgBiBr 6 double perovskite NCs adopting a facile hot injection approach. The as-prepared NCs could keep their structure stable either in air for more than two months or being heated at 300 °C in ambient atmosphere for 3 h. Moreover, Cs 2 AgBiBr 6 NCs were investigated for photocatalytic NO removal under visible-light irradiation, achieving an exciting removal rate of 97%, which is much higher than the previous reports as we know. In addition, the Cs 2 AgBiBr 6 NCs demonstrated outstanding recyclability for at least four cycles in NO removal. The photocatalytic mechanism of Cs 2 AgBiBr 6 NCs was further proposed. This investigation offers a new environmental photocatalyst to purify the air. [ABSTRACT FROM AUTHOR]

The Lead-free all-inorganic double perovskite Cs 2 AgBiBr 6 is regarded as an attractive alternative to lead-based organic-inorganic counterparts in perovskite solar cells (PSCs) because of the superb durability, nontoxicity and distinct optical properties. Nevertheless, the power conversion efficiencies (PCEs) of Cs 2 AgBiBr 6 -based cells are significantly limited by both inherent and external defects in Cs 2 AgBiBr 6 films caused by structural/optical features and fabrication processes, respectively. Thus, it is necessary to conduct a review to enhance fundamental knowledge regarding the decisive performance-limiting factors and relevant performance improvement strategies of Cs 2 AgBiBr 6 -based PSCs. Herein, fundamental knowledge of the decisive performance-limiting factors and relevant origins of Cs 2 AgBiBr 6 -based PSCs is presented, including inferior sunlight absorption capability, inferior film quality, high defect amount and unsuitable energy level alignment. On this basis, some distinct strategies to improve the PCEs of Cs 2 AgBiBr 6 -based cells are proposed such as dye sensitization, band gap regulation, interface control, additive engineering and (anti-)solvent design. Finally, the remaining key problems and future research directions of Cs 2 AgBiBr 6 -based PSCs are provided. Our review aims to present important guidance for future research on Cs 2 AgBiBr 6 -based PSCs to break the efficiency record. [Display omitted] • The superiorities of Cs 2 AgBiBr 6 -based PSCs over Pb-based counterparts are illustrated. • The fundamental understanding of the decisive performance-limiting factors is presented. • Several distinct strategies to enhance the performance of Cs 2 AgBiBr 6 -based PSCs have been proposed. • The remaining key problems and future directions of Cs 2 AgBiBr 6 -based PSCs are discussed. [ABSTRACT FROM AUTHOR]

Cs 2 AgBiBr 6 , a double perovskite structure, offers potential as a stable and non-toxic alternative to organic lead perovskites. However, challenges such as poor film quality and a wide indirect band gap have limited its applications. In this study, we introduced Co2+ cations into the precursor solution to slow down Cs 2 AgBiBr 6 film crystallization kinetics. This intervention led to improved film quality, larger grain sizes, reduced defect densities, band gap modulation, and increased solar cell efficiency. Additionally, Co2+ B-site substitution effectively reduced bromine vacancies in the pristine perovskite, mitigating carrier defect recombination. Co2+ also lowered the band gap of Cs 2 AgBiBr 6 and adjusted energy level arrangements, facilitating carrier transport, enhancing electron-hole extraction, and improving conductivity. We investigated the optimal Co2+ addition ratio and elucidated the enhancement mechanisms. The introduction of Co2+ increased power conversion efficiency from 2.11 % to 3.50 % and short-circuit current density from 3.88 to 4.88 mA/cm2. This study offers a straightforward method to enhance Cs 2 AgBiBr 6 -based solar cells. • Introducing Co2+ modified inorganic lead-free Cs 2 AgBiBr 6 perovskite films. • The modified method improved the crystallinity of Cs 2 AgBiBr 6 perovskite film. • The band gap of perovskite was adjusted by introducing Co2+ to better match energy levels. • The Cs 2 AgBiBr 6 perovskite solar cell device with Co2+ has a PCE of 3.5 %. [ABSTRACT FROM AUTHOR]