Lead-based Halide Perovskites Research Articles

Enhanced Responsivity and Photostability of Cs3Bi2I9-Based Self-Powered Photodetector via Chemical Vapor Deposition Engineering.

Lead-based halide perovskites have gained significant prominence in recent years in optoelectronics and photovoltaics, owing to their exceptional optoelectronic properties. Nonetheless, the toxicity of lead (Pb) and the stability concern pose obstacles to their potential for future large-scale market development. Herein, stable lead-free Cs3Bi2I9 (CBI) films are presented with smooth and compact morphologies synthesized via chemical vapor deposition (CVD), demonstrating their application as an UV photodetector in a self-powered way. The self-powered photodetectors (SPDs) exhibit remarkable characteristics, including a responsivity of 1.57 AW-1 and an impressive specific detectivity of 3.38 × 1013 Jones under the illumination of 365nm at zero bias. Furthermore, the SPDs exhibit a nominal decline (≈2.2%) in the photocurrent under constant illumination over 500h, highlighting its impressive long-term operational stability. Finally, the real-time UV-detection capability of the device is demonstrated by measuring the photocurrent under various conditions, including room light and sunlight at different times. These findings offer a new platform for synthesizing stable and high-quality perovskite films, and SPDs for advancing the development of wearable and portable electronics.

Effect of Mn2+ doping and DDAB-assisted postpassivation on the structural and optical properties of CsPb(Cl/Br)3 halide perovskite nanocrystals

Cesium lead halide perovskite (CsPbX3; X = Cl, Br, I) nanocrystals showing intense band-edge emission and high photoluminescence quantum yield are known to be a potential candidate for application in optoelectronic devices. However, controlling toxicity due to the presence of Pb2+ in lead-based halide perovskites is a major challenge for the environment that needs to be tackled cautiously. In this work, we have partially replaced Pb2+ with Mn2+ ions in the CsPb(Cl/Br)3 nanocrystals and investigated their impact on the structural and optical properties. The Rietveld refinement shows that CsPbCl2Br nanocrystals possess a cubic crystal structure with Pm 3̅ m space group, the Mn2+ doping results in the contraction of the unit cell. The CsPb(Cl/Br)3: Mn nanocrystals show a substantial change in the optical properties with an additional emission band at ∼588 nm through a d-d transition, changing the emission color from blue to pink. Here, a didodecyldimethylammonium bromide (DDAB) ligand that triggers both anion and ligand exchange in the CsPb(Cl/Br)3: Mn nanocrystals have been used to regulate the exchange reaction and tune the emission color of halide perovskites by changing the peak position and the PL intensities of band-edge and Mn2+ defect states. We have also shown that oleic acid helps in the desorption of oleylamine capping from the CsPb(Cl/Br)3: Mn nanocrystal surfaces and DDAB, resulting in the substitution of Cl− with Br− as well as provides capping with shorter branched length ligand which led to increase in the overall PL intensity by many folds.

Comprehensive investigation of material properties and operational parameters for enhancing performance and stability of FASnI3-based perovskite solar cells

Recent advancements in the efficiency of lead-based halide perovskite solar cells (PSCs), exceeding 25%, have raised concerns about their toxicity and suitability for mass commercialization. As a result, tin-based PSCs have emerged as attractive alternatives. Among diverse types of tin-based PSCs, organic–inorganic metal halide materials, particularly FASnI3 stands out for high efficiency, remarkable stability, low-cost, and straightforward solution-based fabrication process. In this work, we modelled the performance of FASnI3 PSCs with four different hole transporting materials (Spiro-OMeTAD, Cu2O, CuI, and CuSCN) using SCAPS-1D program. Compared to the initial structure of Ag/Spiro-OMeTAD/FASnI3/TiO2/FTO, analysis on current–voltage and quantum efficiency characteristics identified Cu2O as an ideal hole transport material. Optimizing device output involved exploring the thickness of the FASnI3 layer, defect density states, light reflection/transmission at the back and front metal contacts, effects of metal work function, and operational temperature. Maximum performance and high stability have been achieved, where an open-circuit voltage of 1.16 V, and a high short-circuit current density of 31.70 mA/cm2 were obtained. Further study on charge carriers capture cross-section demonstrated a PCE of 32.47% and FF of 88.53% at a selected capture cross-section of electrons and holes of 1022 cm2. This work aims to guide researchers for building and manufacturing perovskite solar cells that are more stable with moderate thickness, more effective, and economically feasible.

Organic-Inorganic Hybrid Cuprous-Based Metal Halides with Unique Two-Dimensional Crystal Structure for White Light-Emitting Diodes.

Ternary cuprous (Cu+)-based metal halides, represented by cesium copper iodide (e.g., CsCu2I3 and Cs3Cu2I5), are garnering increasing interest for light-emitting applications owing to their intrinsically high photoluminescence quantum yield and direct band gap. Toward electrically driven light-emitting diodes (LEDs), it is highly desirable for the light emitters to have a high structural dimensionality as it may favor efficient electrical injection. However, unlike lead-based halide perovskites whose light-emitting units can be facilely arranged in three-dimensional (3D) ways, to date, nearly all ternary Cu+-based metal halides crystallize into 0D or 1D networks of Cu-X (X=Cl, Br, I) polyhedra, whereas 3D and even 2D structures remain mostly uncharted. Here, by employing a fluorinated organic cation, we report a new kind of ternary Cu+-based metal halides, (DFPD)CuX2 (DFPD+=4,4-difluoropiperidinium), which exhibits unique 2D layered crystal structure. Theoretical calculations reveal a highly dispersive conduction band of (DFPD)CuBr2, which is beneficial for charge carrier injection. It is also of particular significance to find that the 2D (DFPD)CuBr2 crystals show appealing properties, including improved ambient stability and an efficient warm white-light emission, making it a promising candidate for single-component lighting and display applications.

A Double Perovskite Single Crystal CsCuAgI3.

Eco-friendly halide double perovskites are attracting significant attention as potential substitutes for traditional lead-based halide perovskites. However, their typically wide or indirect band gap limits further technological advancement. This study presents a new, eco-friendly, all-inorganic millimeter-scale CsCuAgI3 single crystal (SC). The crystal exhibits a direct band gap of 2.02 eV at the G-point, markedly superior to that of traditional double perovskites. The absorption and photoluminescence spectra further corroborate its band gap attributes. Owing to the B-site Cu-Ag disorder, the crystal possesses a higher Urbach energy (119 meV), indicative of structural disorder. CsCuAgI3 exhibits a wide Stokes shift of 230 nm, a wide full width at half-maximum (fwhm) of 152 nm, a long fluorescence lifetime of 7.29 μs, and excellent stability. In addition, a photoelectric detection prototype was prepared using a CsCuAgI3 single crystal. Using a 375 nm laser as the excitation source, the device showed a very sensitive photoelectric response, clocking in at (0.37/0.21) seconds. This work offers new insights into developing novel lead-free double perovskite single crystals and exploring their potential applications.

High performance CsBi3I10/PCBM bulk heterojunction perovskite photodetector.

Lead halide perovskites (LHPs) have been extensively studied due to their remarkable optoelectronic performance. However, the toxicity of a lead ion to humans and its instability under ambient conditions render lead-based halide perovskite an unsuitable material for commercialization. Meanwhile, lead-free halide perovskite (LFHP) devices generally exhibit poor performance. Therefore, enhancing photoelectric conversion capacity is the most important issue that needs to be addressed. Here, we propose a photodetector (PD) fabricated using C s B i 3 I 10/p h e n y l-C 61-butyric acid methyl ester (PCBM) bulk heterojunction as the active layer. The PD illuminated under 532nm can reach a high responsivity (1.54A/W) at -2V bias, while at 2V bias, the PD reaches a higher responsivity (224.40A/W). All of those results suggest that C s B i 3 I 10/P C B M bulk heterojunctions hold enormous potential in substituting for LHPs in optoelectronic devices.

Effect of Sb-Bi alloying on electron-hole recombination time of Cs2AgBiBr6 double perovskite.

The double perovskite material Cs2AgBiBr6, characterized by high stability, low toxicity, and excellent optoelectronic properties, has emerged as a promising alternative to lead-based halide perovskites in photovoltaic applications. However, its photovoltaic conversion efficiency after integration into solar cell devices is less than 3%, significantly lower than that of traditional perovskite solar cells. While alloying methods have been widely applied in the design of photovoltaic materials, their specific role in modulating the lifetime of photo-generated charge carriers in double-perovskite solar cells remains inadequately explored. In this study, through nonadiabatic molecular dynamics (NAMD) simulations, the excited-state dynamics properties of Cs2AgBiBr6 and alloyed Cs2AgSb0.375Bi0.625Br6 samples were compared. The results revealed that the introduction of Sb ions into the double perovskite structure induces lattice deformation upon heating to 300 K, leading to distortion of Bi-Br bonds and enhanced valence band delocalization. Using the decoherence-induced surface hopping method, the capture and recombination processes of charge carriers between different states were simulated. It was suggested that hole lifetime serves as the primary limiting factor for carrier lifetime in Cs2AgBiBr6, and replacing 0.375 proportion of Bi with Sb can decelerate the hole capture rate, extending carrier lifetime by 3-4 times. This study demonstrates that alloying offers a viable approach to optimizing the optoelectronic performance of the Cs2AgBiBr6 perovskite, thereby advancing the application of double perovskite materials in the field of photovoltaics.

Numerical simulation and performance optimization of a lead-free inorganic perovskite solar cell using SCAPS-1D

The perovskite solar cells, founded on lead halides, have garnered significant attention from the photovoltaic industry owing to their superior efficiency, ease of production, lightweight characteristics, and affordability. However, due to the hazardous nature of lead-based compounds, these solar cells are currently unsuitable for commercial production. In this context, a lead-free perovskite, cesium-bismuth iodide (Cs3Bi2I9) is considered as a potential alternative to the lead halide-based cell due to their non-toxicity and stability, but this perovskite cannot be matched with random hole transport layer (HTL) and electron transport layer (ETL) materials compared to lead halide-based perovskite because of their crystal structure and band gap. Therefore, in this study, performance comparison of different ideal HTL and ETL materials for Cs3Bi2I9 perovskite layer were studied using SCAPS-1D device simulation on the basis of open circuit voltage, short circuit current, power conversion efficiency (PCE) and fill factor (FF) as well as several novel PSC configuration models were designed that can direct for further experimental research for PSC device commercialization. Results from this investigation reveals that the maximum efficiency of 20.96 % is obtained for the configuration ITO/WS2/Cs3Bi2I9/NiO/Au with optimized parameters such as thickness 400 nm, band gap 2.1eV, absorber layer defect density 1012 cm−3, donor density of ETL 1018 cm−3 and the acceptor density of HTL 1020 cm−3.

Physically realistic, parametric model for excitonic critical point parabolic band oscillators

Critical point parabolic band (CPPB) oscillators are often useful to model the optical response of semiconductor materials, such as hybrid organic–inorganic lead halide-based perovskites, to incident photons in the form of the complex dielectric function (ε=ε1+iε2) spectra. Some models of ε using CPPB oscillators are not guaranteed Kramers–Kronig (KK) consistent (and therefore not physically realistic), may have excess or arbitrary parameter values, or may require prohibitively long computational time when used to fit ellipsometric spectra. For excitonic CPPBs, commonly used to describe the optical response of hybrid organic–inorganic lead halide-based perovskite materials, a physically realistic, parametric model of ε is developed from the KK relationship between ε1 and ε2 for a number of CPPB oscillators with an Urbach tail below the lowest direct transition. This parametric model is shown to produce the same line shape reported from previous works accurately and more quickly than other available KK-consistent CPPB models.

Observation on structural and optical features of new nanostructured lead-free methylammonium zinc or cobalt iodide perovskites for solar cells applications

The toxicity of lead-based halide perovskites has become a significant drawback to be employed in optoelectronic devices. Therefore, developing other environmentally friendly candidates with tunable optoelectronic properties for highly efficient solar cells is indispensable. Lead-free perovskite solar cells (PSCs) are promising to have a crucial role in large-scale commercial non-toxic photovoltaic devices. Here, the microstructure and optoelectronic properties of 2D halide perovskites without pb (CH3NH3)2BI4 (where B = Zn or Co) have been investigated for use in solar cells. The synthesized samples are characterized by X-ray diffraction (XRD), Raman spectroscopy, FT-IR, FESEM, and TEM. The variation in the optical and photoluminescence (PL) is recognized. The results indicate that (CH3NH3)2ZnI4 and (CH3NH3)2CoI4 crystals demonstrate a wide band gap of about 2.42 and 1.87 eV, respectively. A comparative study is presented for the optical properties of Zn- versus Co-based perovskites. It is noticed that Co is a better candidate than Zn to be a good replacement choice for Pb as Co-containing compounds have lower optical bandgap than Zn-containing compounds. PCBM is employed as a hole transport material, and PEDOT:PSS as an electron transport layer. The p-i-n PSCs are fabricated, and the electrical parameters are measured, obtaining power conversion efficiencies (PCE) of 0.73 and 2.45% for (CH3NH3)2ZnI4 and (CH3NH3)2CoI4, respectively. This work opens the door for further investigations to increase the PCE of both devices.

A novel, highly-efficient, eco-friendly, and relatively stable Cs2AgFeCl6 photocatalyst for degradation of organic dyes

Lead-based halide perovskite is considered to be a potential visible-light-activated photocatalyst owing to its excellent optoelectronic properties. However, the toxicity of lead and the instability of the material restrict its wide application in the field of photocatalysis. A double perovskite structure is thought to be a solution to this problem. The authors prepared a series of samples, including Cs2AgInCl6, Cs2AgIn1−xFexCl6, and Cs2AgFeCl6 through co-precipitation in acidic solutions. The effects of Fe3+ doping on the crystal structure and morphology of Cs2AgInCl6 were characterized by XRD and SEM. Based on density functional theory, VB-XPS and UV-Vis absorption characterizations, the band structure of Cs2AgInCl6 and Cs2AgFeCl6 were determined, showing that the bandgap of Cs2AgIn1−xFexCl6 was reduced linearly by Fe3+ doping. And Sudan Red III can be photocatalytically degraded by all samples under concentrated xenon lamp irradiation of 175 W, with Cs2AgFeCl6 degrading 96% of Sudan Red III in 45 min. In addition, the Cs2AgFeCl6 sample exhibits good cyclic stability and does not demonstrate any significant changes after two months in storage, showing that Cs2AgFeCl6 may serve as an effective and relatively stable Xenon lamp-activated photocatalyst in degradation of organic dyes.

Lead-Free Halide Perovskite Nanocrystals for Light-Emitting Diodes.

Lead-based halide perovskite nanocrystals (PeNCs) have demonstrated remarkable potential for use in light-emitting diodes (LEDs). This is because of their high photoluminescence quantum yield, defect tolerance, tunable emission wavelength, color purity, and high device efficiency. However, the environmental toxicity of Pb has impeded their commercial viability owing to the restriction of hazardous substances directive. Therefore, Pb-free PeNCs have emerged as a promising solution for the development of eco-friendly LEDs. This review article presents a detailed analysis of the various compositions of Pb-free PeNCs, including tin-, bismuth-, antimony-, and copper-based perovskites and double perovskites, focusing on their stability, optoelectronic properties, and device performance in LEDs. Furthermore, we address the challenges encountered in using Pb-free PeNC-LEDs and discuss the prospects and potential of these Pb-free PeNCs as sustainable alternatives to lead-based PeLEDs. In this review, we aim to shed light on the current state of Pb-free PeNC LEDs and highlight their significance in driving the development of eco-friendly LED technologies.

Direct band-gap iodide double perovskite solar cell materials by doping strategy: First-principles predictions

As alternatives to lead-based halide perovskite materials, the lead-free halide double-perovskite materials have many advantages but often show wide indirect band gaps and exceed the optimum band-gap range of 0.9–1.6 eV. Based on first-principles calculations, we scan a serial of halide double-perovskites Cs2B′B''X6 (B′ = Li, Na, K; B'' = In, Bi; X = Cl, Br, I) and find that most of Cs2B′B''X6 double-perovskite materials have direct band gaps but larger than 1.6 eV, while the direct band gaps of Cs2LiInI6 and Cs2NaInI6 are smaller than 0.9 eV. We modulate the electronic structure of Cs2B′InI6 (B′ = Li, Na, K) by an ionic doping strategy through substituting partial In ions with Bi ions and discover more halide double-perovskite solar cell materials with suitable band gap. By exploring the stability, electronic structures and optical properties of the doped double-perovskite Cs2B′In1-xBixI6 (B′ = Li, Na, K, x = 0.25 and 0.75), we discover the Cs2B′In0.75Bi0.25I6 (B′ = Li, Na and K) DP materials show direct band gaps within the optimal band-gap range of 0.90 − 1.60 eV for promising solar-cell materials. Meanwhile, the doped Cs2B′In1-xBixI6 DP materials show good carrier mobility as high as 103 cm2S−1V−1. Moreover, the predicted new materials exhibit excellent light absorption coefficients of 106 cm−1 in the visible light range. These new lead-free inorganic DP materials may offer great promise as candidates for highly efficient solar absorber materials for photovoltaic applications.

Performance and stability optimization of CsPbCl3-yIy (y = 0, 1, 2, and 3) lead-based perovskites solar cells using SCAPS-1D

Recently, lead-based halide perovskites have aroused a great deal of interest as a promising material for optoelectronic applications because of their low cost and excellent energy conversion efficiency. In this study, we optimized the performance and stability of solar cells based on lead halide perovskites CsPbCl3-yIy (y = 0, 1, 2, and 3) by examining various parameters, such as the defect density and thickness of the absorbing layers, the work function of the back contact, the series and shunt resistances and the operating temperature. We performed a comparative study using the SCAPS simulation software. Our optimization of the solar cell parameters resulted in a power conversion efficiency of 26.29% for FTO/TiO2/CsPbI3/MoO3/Au, 17.47% for FTO/TiO2/CsPbI2Cl/MoO3/Au, 14.75% for FTO/SnO2/CsPbCl2I/Cu2O/Au, and 14.20% for FTO/SnO2/CsPbCl3/Cu2O/Au. These results indicate that perovskite solar cells based on CsPbI3 show better performance, but they are still very sensitive to high temperatures. In contrast, perovskite solar cells based on CsPbCl3 and CsPbCl2I show a more modest performance but are more stable. Replacing iodine with chlorine is an optimal solution for enhancing stability. Our simulation results provide a key starting point for further studies on solar cells based on lead halide perovskites CsPbCl3-yIy (y = 0, 1, 2, and 3).

Heavy pnictogens-based perovskite-inspired materials: Sustainable light-harvesters for indoor photovoltaics

The need for self-powered electronics is progressively growing in parallel with the flourishing of the Internet of Things (IoT). Although batteries are dominating as powering devices, other small systems, such as piezoelectric, thermoelectric, and photovoltaic systems, are attracting attention. These last ones can be adapted from their classical outdoor configuration to work preferentially under indoor illumination, i.e., by harvesting the spectrum emitted by LEDs and/or fluorescent lamps. However, crystalline silicon, the classical photovoltaic material for solar panels, has a bandgap not suitable for ensuring good efficiency with such spectra. With wider bandgaps, other semiconductors can come into play for this task. Still, the materials of choice, having to be integrated within households, should also satisfy the criterion of non-toxicity and maintain low-cost production. While lead-based halide perovskites cannot represent a valuable solution for this scope, due to the strong environmental and health concerns associated with the presence of Pb, analogous compounds based on the heaviest pnictogens, i.e., bismuth and antimony, could work as sustainable light-harvesters for indoor photovoltaic devices. In this Review, we focus on reporting the most recent developments of three compounds of this class: The double perovskite Cs2AgBiBr6 is first chosen as a model system for the other two, which are emerging perovskite-inspired materials, namely, Cs3Sb2I9−xClx and bismuth oxyiodide. We show the potential of these semiconductors to play a crucial role in the future market of self-powering IoT devices, which will become a large class of devices in the electronics industry in the upcoming years.

Recent Advances in the Synthesis and Application of Vacancy-Ordered Halide Double Perovskite Materials for Solar Cells: A Promising Alternative to Lead-Based Perovskites.

Lead-based halide perovskite materials are being developed as efficient light-absorbing materials for use in perovskite solar cells (PSCs). PSCs have shown remarkable progress in power conversion efficiency, increasing from 3.80% to more than 25% within a decade, showcasing their potential as a promising renewable energy technology. Although PSCs have many benefits, including a high light absorption coefficient, the ability to tune band gap, and a long charge diffusion length, the poor stability and the toxicity of lead represent a significant disadvantage for commercialization. To address this issue, research has focused on developing stable and nontoxic halide perovskites for use in solar cells. A potential substitute is halide double perovskites (HDPs), particularly vacancy-ordered HDPs, as they offer greater promise because they can be processed using a solution-based method. This review provides a structural analysis of HDPs, the various synthesis methods for vacancy-ordered HDPs, and their impact on material properties. Recent advances in vacancy-ordered HDPs are also discussed, including their role in active and transport layers of solar cells. Furthermore, valuable insights for developing high-performance vacancy-ordered HDP solar cells are reported from the detailed information presented in recent simulation studies. Finally, the potential of vacancy-ordered HDPs as a substitute for lead-based perovskites is outlined. Overall, the ability to tune optical and electronic properties and the high stability and nontoxicity of HDPs have positioned them as a promising candidate for use in photovoltaic applications.

Effects of metals (X = Be, Mg, Ca) encapsulation on the structural, electronic, phonon, and hydrogen storage properties of KXCl3 halide perovskites: Perspective from density functional theory

To overcome the challenges surrounding toxic and unstable lead-based halide perovskites, it is important to develop promising non-toxic s-block halide perovskites that can serve as an alternative in optoelectronic applications. Therefore, based on density functional theory (DFT), the structural, electronics, optical, phonon, and thermodynamic properties of the potassium-based halide perovskites KBeCl3, KCaCl3, and KMgCl3 have been examined through utilization of the PBE + GGA method to determine the stability, thermodynamics as well as the optoelectronic applications of these perovskites. The calculated lattice constants for KBeCl3, KCaCl3, and KMgCl3 were 4.41 Å, 5.10 Å, and 4.74 Å respectively. The band structure and the density of state of the studied materials displayed narrow and indirect band gaps. Furthermore, optical property calculations such as the real part ε1 (ω), and imaginary part ε2 (ω) of the dielectric function ε (ω) along with the absorption coefficient α (ω), and the refractive index n (ω) of dielectric function were carried out. In terms of stability, the phonon frequency calculations show that dynamic stability increases as we move down the group on the periodic table for the s-block halide perovskites, indicating that KMgCl3 and KCaCl3 have the highest stability and are better candidates for optoelectronic applications. Thermodynamic parameters show an absolute dependence on temperature. The gravimetric hydrogen storage capacity was computed to be 5.866%, 4.516%, and 3.649% for KBeH3, KMgH3, and KCaH3 respectively. It is observed that gravimetric density increases with decreasing cationic size: Be, Mg, and Ca. Furthermore, KBeH3 perovskite is computed as the highest amongst the studied materials are suitable and effective long term hydrogen storage as a fuel due to its relatively higher gravimetric ratios.

Molecular Tailoring of Pyridine Core-Based Hole Selective Layer for Lead Free Double Perovskite Solar Cells Fabrication.

To solve the toxicity issues related to lead-based halide perovskite solar cells, the lead-free double halide perovskite Cs2AgBiBr6 is proposed. However, reduced rate of charge transfer in double perovskites affects optoelectronic performance. We designed a series of pyridine-based small molecules with four different arms attached to the pyridine core as hole-selective materials by using interface engineering. We quantified how arm modulation affects the structure-property-device performance relationship. Electrical, structural, and spectroscopic investigations show that the N3,N3,N6,N6-tetrakis(4-methoxyphenyl)-9H-carbazole-3,6-diamine arm's robust association with the pyridine core results in an efficient hole extraction for PyDAnCBZ due to higher spin density close to the pyridine core. The solar cells fabricated using Cs2AgBiBr6 as a light harvester and PyDAnCBZ as the hole selective layer measured an unprecedented 2.9% power conversion efficiency. Our computed road map suggests achieving ∼5% efficiency through fine-tuning of Cs2AgBiBr6. Our findings reveal the principles for designing small molecules for electro-optical applications as well as a synergistic route to develop inorganic lead-free perovskite materials for solar applications.

Expanding the Absorption of Double Perovskite Cs2AgBiBr6 to NIR Region.

The toxicity of lead-based halide perovskites hampers broad application in optoelectronics. The lead-free perovskite Cs2AgBiBr6 is considered a promising candidate, owing to its long carrier lifetime and outstanding stability. However, the relatively large bandgap hinders its absorption in the visible region and thus the application of its photoelectric properties in the visible and near-infrared (NIR) regions. Therefore, the expansion of absorption to the longer wavelengths, even the NIR region, makes sense for solar cells and photodetector applications. Facile elemental doping or substitution of Cs2AgBiBr6 makes it potentially desirable for applications in both visible and NIR regions. As a result, band-edge adjustment to expand the absorption onset or trace deep-energy-level doping with a new intermediate band was achieved. Here, we summarize the elemental doping results and review the potential application of Cs2AgBiBr6 from these two aspects and give constructive perspectives for further development of lead-free perovskite.

Recent Advances and Future Perspectives of Lead-Free Halide Perovskites for Photocatalytic CO2 Reduction.

It is still challenging to design and develop the state-of-the-art photocatalysts toward CO2 photoreduction. Enormous researchers have focused on the halide perovskites in the photocatalytic field for CO2 photoreduction, due to their excellent optical and physical properties. The toxicity of lead-based halide perovskites prevents their large-scale applications in photocatalytic fields. In consequence, lead-free halide perovskites (LFHPs) without the toxicity become the promising alternatives in the photocatalytic application for CO2 photoreduction. In recent years, the rapid advances of LFHPs have offer new chances for the photocatalytic CO2 reduction of LFHPs. In this review, we summarize not only the structures and properties of A2 BX6 , A2 B(I)B(III)X6 , and A3 B2 X9 -type LFHPs but also their recent progresses on the photocatalytic CO2 reduction. Furthermore, we also point out the opportunities and perspectives to research LFHPs photocatalysts for CO2 photoreduction in the future.