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7132102 
Journal Article 
Two-Dimensional 111-Type In-Based Halide Perovskite Cs3In2X9 (X = Cl, Br, I) with Optimal Band Gap for Photovoltaics and Defect-Insensitive Blue Emission 
Guo, Wenhui; Shi, Junjie; Zhu, Yaohui; Wu, M; Du, J; Cen, YuL; Liu, ShiM; Han, ShuP; , 
2020 
AMER PHYSICAL SOC 
COLLEGE PK 
WOS:000513244400005 
Despite rapid progress in the power-conversion efficiency of Pb-based perovskite solar cells, both the long-term instability and Pb toxicity are still the main challenges for their commercial applications. Here, by first-principles GW calculations, we find three kinds of two-dimensional (2D) 111-type Pb-free In-based halide perovskites of the form Cs3In2X9 (X = Cl, Br, I) as promising alternatives to the star material CH3NH3PbI3 (MAPbI(3)) because of the following excellent electronic, optical, and transport properties: (i) The 2D In-based halide perovskites are environmentally friendly lead-free materials. (ii) Compared with MAPbX(3), they have greater structural stability. (iii) As energetic photovoltaic materials, 2D Cs3In2I9 perovskites are direct-band-gap semiconductors with optimal band gaps from 1.25 eV (trilayer) to 1.47 eV (monolayer). (iv) The 2D Cs3In2X9 perovskites have ideal band structures for solid-state lighting with a wide direct-optical-band-gap range (approximately 0.94-3.54 eV), covering the whole visible-light region, and light electron (heavy hole) effective mass, which will directly enhance the defect-insensitive emission efficiency due to the localization of holes. Particularly, Cs3In2BrxCl9-x has a suitable direct optical band gap for highly desired blue emission. (v) The absorption coefficient of Cs3In2X9 is up to 7 x 10(4) cm(-1), which is between that of GaAs (10(4) cm(-1)) and that of MAPbI(3) (10(5) cm(-1)). (vi) The estimated power-conversion efficiency in Cs3In2I9 reaches 28%, which is close to that of MAPbI(3) (30%). These findings pave a way for designing nontoxic, stable, and high-performance photovoltaic and light-emitting devices.