A computational study of self-trapped excitons in metal halide perovskites*

Recently, a series of lead-free halide perovskites with efficient broad band emission have been discovered, which show promise for photovoltaic applications [1]. These discoveries have motivated many studies of the electronic structure of these systems; however, several controversies are present in the literature regarding the level of first-principles electronic structure theory required to accurately describe emission processes from self-trapped excitons in halide perovskites. We present a systematic study of the electronic properties of Cs₄SnX₆(X=Br;I) and Cs₂AgInCl₆ using hybrid density functional theory (DFT), and we compare results obtained with constrained DFT and time-dependent DFT for photoluminescence spectra. We discuss the sensitivity of the results to the choice of hybrid functionals (including HSE [2] and dielectric-dependent hybrid [3]), and we show that TDDFT and CDFT yield results that differ by up to 0.5 eV for energy gaps, for the systems considered here. We also discuss comparisons with experiments conducted at different temperatures.

 

[1]. Jia-Ming Meng, et. al. JPC Letters 2021 12 (36), 8763-8769

[2]. Jochen Heyd and Gustavo E. Scuseria, J. Chem. Phys 118, 8207, (2003)

[3]. J. H. Skone, M. Govoni and G. Galli, Physical Review B, 89, 195112 (2014)