Near‐Infrared Light‐Responsive Cu‐Doped Cs₂AgBiBr₆

Abstract

Lead‐free halide double perovskites (A2BIBIIIX6) with attractive optical and electronic features are considered to be a promising candidate to overcome the toxicity and stability issues of lead halide perovskites (APbX3). However, their poor absorption profiles limit device performance. Here the absorption band edge of Cs2AgBiBr6 double perovskite to the near‐infrared range is significantly broadened by developing doped double perovskites, Cs2(Ag:Cu)BiBr6. The partial replacement of Ag ions by Cu ions in the crystal lattice is confirmed by the X‐ray photoelectron spectroscopy (XPS) and solid‐state nuclear magnetic resonance (ssNMR) measurements. Cu doping barely affects the bandgap of Cs2AgBiBr6; instead it introduces subbandgap states with strong absorption to the near‐infrared range. More interestingly, the near‐infrared absorption can generate band carriers upon excitation, as indicated by the photoconductivity measurement. This work sheds new light on the absorption modulation of halide double perovskites for future efficient optoelectronic devices.

Reconstructing Reliable Powder Patterns from Spikelets (Q)CPMG NMR Spectra: Simplification of UWNMR Crystallography Analysis

“…Lead diformate—Pb(HCOO) 2 —was obtained according to the description provided in [ 35 ]. Cesium silver(I) bismuth(III) bromide—Cs 2 AgBiBr 6 —was synthetized by the procedure described in the literature data [ 41 ]. Bis( μ 2 - t -butanolato)-dichloro-dimethyl-di-gallium—[Cl(Me)Ga(O t Bu)] 2 (CAJXOC in CCDC database)—was prepared from the following chemicals: lithium bis(trimethylsilyl)amide solution in toluene (0.5 M), anhydrous toluene, and t -butanol, bought from Sigma-Aldrich, (St. Louis, MO, USA), gallium trichloride, ultra-dry, from Alfa Aesar (Haverhill, MA, USA).…”

All‐Inorganic Lead‐Free Perovskite(‐Like) Single Crystals: Synthesis, Properties, and Applications

“…Figure a displays the as‐prepared Cu:Cs 2 AgBiBr 6 single crystals with various amounts of Cu 2+ , demonstrating that the Cu 2+ dopants could not affect the cubic crystal structure of Cs 2 AgBiBr 6 . [ 109 ] However, it is clear that the increase of Cu 2+ dopants darkening the color of single crystals, which is due to the strong absorption in the near‐infrared range induced by the Cu 2+ ions incorporation. Figure 5b shows the Cs 2 AgBiBr 6 single crystals with alkali ions (K + , Na + , Rb + ) substitution and their bare effect on the crystal structures and indirect bandgaps are confirmed by the characteristics.…”

“…Reproduced with permission. [ 109 ] Copyright 2020, Wiley‐VCH GmbH. b) Photographs of (Cs 1− x Y x ) 2 AgBiBr 6 (Y = Cs, Rb, K, Na) single crystals.…”

“…Figure 10d displays the change of Cu:Cs 2 AgBiBr 6 absorption spectra with the increase of Cu 2+ dopants. [ 109 ] While the undoped Cs 2 AgBiBr 6 shows a sharp absorption edge at 610 nm, clear absorption tails are observed at 860 nm for Cu‐doped perovskite single crystals, mainly due to the incorporation of a defect energy level induced by Cu 2+ doping in the sub‐bandgap. Zou and co‐workers introduced high pressures on a hexagonal Cs 3 Bi 2 I 9 single crystal to investigate the effect of pressure on its optical performance.…”

“…Reproduced with permission. [ 109 ] Copyright 2020, Wiley‐VCH GmbH. e) Changes of absorption spectra for Cs 3 Bi 2 I 9 single crystals under high pressures.…”