Disappeared deep charge-states transition levels in the p-type intrinsic CsSnCl3 perovskite

Abstract

Lead-free inorganic perovskites are promising for optoelectronic applications. Understanding their phase diagram and defect properties is beneficial to predict the stable phase and applications. Here, taking CsSnCl3 as an example, the stability and defect properties are investigated systemically. The results show that the stoichiometric CsSnCl3 can only be grown in a narrow area determined by Sn and Cs chemical potentials. No matter what the Sn condition is, both acceptor defects (Cs- and Sn-vacancies with low charge states) are formed spontaneously with negative formation energies, and the donor defects are difficult to be formed with high formation energies. Interestingly, these charge-state transition levels induced by such stable defects are in the valence band. Meanwhile, no deep acceptor and donor states are formed in the bandgap. In addition, although the Fermi levels can vary in a wide range, the Fermi levels are pinned in the valence band, irrespective of the atmospheric conditions, leading to p-type CsSnCl3 with high hole density and low electron density. Such electronic characters are elucidated in detail by the atomic orbitals and structural deformations. Our studies provide an insight view of the defect properties of CsSnCl3 and provide a valuable guideline for CsSnCl3 fabrication and further modulation.