Extending Absorption of Cs<sub>2</sub>AgBiBr<sub>6</sub> to Near‐Infrared Region (≈1350 nm) with Intermediate Band
Ganghong Liu, Zehao Zhang, Cuncun Wu, Yuqing Zhang, Xiangdong Li, Wenjin Yu, Guangjie Yao, Shiming Liu, Junjie Shi, Kaihui Liu, Zhijian Chen, Lixin Xiao, Bo Qu
Abstract
Abstract The toxicity of lead‐based halide perovskites hampers broad application in optoelectronics. Lead‐free perovskite Cs 2 AgBiBr 6 is considered a promising candidate, owing to the long carrier lifetime and great stability. However, the relatively large bandgap of 1.98 eV limits its absorption in the visible region. Herein, Fe 2+ is chosen as the dopant to alloy into Cs 2 AgBiBr 6 single crystals, and results in an absorption range broadening to ≈1350 nm, which is the longest near‐infrared (NIR) response recorded among lead‐free perovskites. About 1% of Fe ions are alloyed into the Cs 2 AgBiBr 6 lattice to cause lattice shrink age. Instead of narrowing the bandgap, Fe doping would introduce a new intermediate band inside the pristine bandgap of Cs 2 AgBiBr 6 to strongly absorb NIR light, as confirmed by third harmonic generation results. Moreover, considerable photogenerated carriers are produced in Fe doped Cs 2 AgBiBr 6 crystals with NIR irradiation. This work has provided a new way to extend the optical response of lead‐free perovskites for NIR photodetectors and intermediate band photovoltaics.