High‐Pressure Band‐Gap Engineering in Lead‐Free Cs₂AgBiBr₆ Double Perovskite

Abstract

Novel inorganic lead‐free double perovskites with improved stability are regarded as alternatives to state‐of‐art hybrid lead halide perovskites in photovoltaic devices. The recently discovered Cs2AgBiBr6 double perovskite exhibits attractive optical and electronic features, making it promising for various optoelectronic applications. However, its practical performance is hampered by the large band gap. In this work, remarkable band gap narrowing of Cs2AgBiBr6 is, for the first time, achieved on inorganic photovoltaic double perovskites through high pressure treatments. Moreover, the narrowed band gap is partially retainable after releasing pressure, promoting its optoelectronic applications. This work not only provides novel insights into the structure–property relationship in lead‐free double perovskites, but also offers new strategies for further development of advanced perovskite devices.

Isothermal pressure-derived metastable states in 2D hybrid perovskites showing enduring bandgap narrowing

“…S15). Such a bandgap evolution trend during decompression relates a different thermodynamic path, suggesting that the structure and properties exhibited by the pressure-treated samples are not memory effects from the high-pressure state (23,24), but are associated with structural reconstruction during decompression. This claim can be further verified by scrutinizing the XRD patterns obtained during the compression and decompression processes.…”

A Review on Energy Band‐Gap Engineering for Perovskite Photovoltaics

“…a) Summary of the applied pressure dependence of bandgaps of perovskite materials . b) The amorphization and 2D XRD images of MAPbBr 3 with various pressures,[27d] Reproduced with permission [27d].…”

“…The complex phases and behavior during compression strongly rely on the specific perovskite material. For example, the bandgap of MAPbI 3 first slightly red‐shifted to 1.507 eV under ≈0.3 GPa and then jumped to 1.63 eV, while Li et al gave a considerable 22.3% reduction for double perovskite Cs 2 AgBiBr 6 …”

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

“…For instance, the cubic Cs 2 AgBiBr 6 double PVK microcrystal and single crystal were first reported by Slavney et al, which owns an indirect bandgap (1.95 eV), a long carrier recombination lifetime (≈660 ns), and a satisfied stability against thermal, light, and moisture, indicating a promising material in optoelectronic applications. Thereafter, the bulk Cs 2 AgBiX 6 (X = Cl, Br) was thoroughly studied to uncover their intrinsic characteristics in both theoretical and experimental aspects . However, to the best of our knowledge, both the synthetic method and optoelectronic characterizations of Cs 2 AgBiBr 6 NCs were still unexplored.…”