Regulating off-centering distortion maximizes photoluminescence in halide perovskites. Issue 9 (30th November 2020)

• Record Type: Journal Article
• Authors: Lü, Xujie; Stoumpos, Constantinos; Hu, Qingyang; Ma, Xuedan; Zhang, Dongzhou; Guo, Songhao; Hoffman, Justin; Bu, Kejun; Guo, Xiaofeng; Wang, Yingqi; Ji, Cheng; Chen, Haijie; Xu, Hongwu; Jia, Quanxi; Yang, Wenge; Kanatzidis, Mercouri G; Mao, Ho-Kwang
• Is Part Of: National science review. Volume 8:Issue 9(2021)
• Publication Date: 2020-11-30
• Subjects: halide perovskites -- high pressure -- off-centering distortion -- optical properties -- lone-pair electrons -- quantitative relationship; Science -- Periodicals; 505
• DOI: 10.1093/nsr/nwaa288
• Languages: English
• ISSNs: 2095-5138

Abstract

Abstract: Metal halide perovskites possess unique atomic and electronic configurations that endow them with high defect tolerance and enable high-performance photovoltaics and optoelectronics. Perovskite light-emitting diodes have achieved an external quantum efficiency of over 20%. Despite tremendous progress, fundamental questions remain, such as how structural distortion affects the optical properties. Addressing their relationships is considerably challenging due to the scarcity of effective diagnostic tools during structural and property tuning as well as the limited tunability achievable by conventional methods. Here, using pressure and chemical methods to regulate the metal off-centering distortion, we demonstrate the giant tunability of photoluminescence (PL) in both the intensity (>20 times) and wavelength (>180 nm/GPa) in the highly distorted halide perovskites [CH3 NH3 GeI3, HC(NH2 )2 GeI3, and CsGeI3 ]. Using advanced in situ high-pressure probes and first-principles calculations, we quantitatively reveal a universal relationship whereby regulating the level of off-centering distortion towards 0.2 leads to the best PL performance in the halide perovskites. By applying this principle, intense PL can still be induced by substituting CH3 NH3 + with Cs + to control the distortion in (CH3 NH3 )1-x Csx GeI3, where the chemical substitution plays a similar role as external pressure. The compression of a fully substituted sample of CsGeI3 further tunes the distortion to the optimal value at 0.7 GPa, which maximizes the emission with a 10-fold enhancement. This work not only demonstrates a quantitative relationship between structural distortion and PL property of the halide perovskites but also illustrates the use of knowledge gained from high-pressure research to achieve the desired properties by ambient methods. Abstract : By regulating the highly distorted halide perovskites using pressure, a quantitative relationship between structural distortion and emission property is demonstrated. The extracted principle is applied to materials design and the results give further support to the revealed relationship.