Atomic and electronic structure of cesium lead triiodide surfaces

TL;DR

This study uses first-principles calculations to analyze the atomic and electronic surface structures of cubic and orthorhombic CsPbI3, revealing stability preferences and surface state characteristics relevant for photovoltaic applications.

Contribution

It provides detailed insights into the surface stability and electronic states of CsPbI3 phases, which were previously not well characterized.

Findings

CsI-terminated surfaces are more stable than PbI2-terminated ones.

Surface reconstructions with added or removed CsI or PbI2 are most stable.

The alpha phase exhibits surface states at the conduction band edge.

Abstract

The (001) surface of the emerging photovoltaic material cesium lead triiodide (CsPbI3 ) is studied. Using first-principles methods, we investigate the atomic and electronic structure of cubic ({\alpha}) and orthorhombic ({\gamma}) CsPbI3 . For both phases, we find that CsI-termination is more stable than PbI2-termination. For the CsI-terminated surface, we then compute and analyse the surface phase diagram. We observe that surfaces with added or removed units of nonpolar CsI and PbI2 are most stable. The corresponding band structures reveal that the {\alpha} phase exhibits surface states that derive from the conduction band. The surface reconstructions do not introduce new states in the band gap of CsPbI3, but for the {\alpha} phase we find additional surface states at the conduction band edge.