Synthesis and Photocatalytic Application of Stable Lead‐Free Cs₂AgBiBr₆ Perovskite Nanocrystals

Abstract

Lead halide perovskite nanocrystals (NCs) have demonstrated great potential as appealing candidates for advanced optoelectronic applications. However, the toxicity of lead and the intrinsic instability toward moisture hinder their mass production and commercialization. Herein, to solve such thorny problems, novel lead-free Cs AgBiBr double perovskite NCs fabricated via a simple hot-injection method are reported, which exhibit impressive stability in moisture, light, and temperature. Such materials are then applied into photocatalytic CO reduction, achieving a total electron consumption of 105 µmol g under AM 1.5G illumination for 6 h. This study offers a reliable avenue for Cs AgBiBr perovskite nanocrystals preparation, which holds a great potential in the further photochemical applications.

Progress of Lead‐Free Halide Double Perovskites

“…[25] Interestingly, the energy required for a direct transition in Cs 2 AgBiBr 6 is lower than that of MAPbBr 3 (2.3 eV). [111] This bandgap value is 0.57 eV higher than that of bulk Cs 2 AgBiBr 6 (1.95 eV). [62,138] Zhou et al obtained an indirect bandgap of 2.52 eV for Cs 2 Ag-BiBr 6 NCs.…”

“…Furthermore, a hydrothermal method, using HCl as the solvent, was reported for the preparation of Cs 2 AgInCl 6 . [111] Copyright 2018, Wiley-VCH. The longer the reaction time, the larger was the crystal size of Cs 2 AgInCl 6 .…”

“…[139] This peak is blue shifted (more than 1 eV) from the band edge. [111] The existence of compounds in such different forms may influence their electronic band structure via quantum confinement effect. Moreover, structural modulation studies have demonstrated the possibility of a pressure dependent bandgap engineering in lead-free double perovskites.…”

“…For example, due to their p-type semiconductor behavior, Cs 2 SnI 6 nanocrystals, with the stable +4 state, have been explored as active layer in solution-processed field effect transistors. [111] However, due to the need to eliminate toxicity and poor stability in perovskite based PV devices, major attention has been paid to the PV application of halide double perovskites. [191] Single crystals of Cs 2 AgBiBr 6 were applied in detectors [181] with high responsivity and outstanding detectivity, comparable to the MAPbX 3 based ones.…”

From Lead Halide Perovskites to Lead‐Free Metal Halide Perovskites and Perovskite Derivatives

“…[55] Second, for B(III) cations, the transition metal cations with multiple oxidation states and/or partially occupied d or f orbitals are not desirable for designing photovoltaic absorbers, because they may introduce deep defect states and too localized band edges. Largesize single crystals, [155,[172][173][174] nanocrystals, [175][176][177][178] and highquality films [179][180][181][182] The element Au is half-colored because it exists only in the compounds A 2 Au 2 X 6 with A = Rb, Cs and X = Cl, Br, I. Most of the reported double perovskites are fluorides and chlorides, [158,159] which generally have too large bandgaps for photovoltaic applications.…”