Surface reconstruction of tetragonal methylammonium lead triiodide

TL;DR

This study uses first-principles density-functional theory to analyze the atomic and electronic structures of the (001) surface of tetragonal methylammonium lead triiodide, exploring different terminations and reconstructions.

Contribution

It provides a detailed computational analysis of surface stability and electronic states of MAPbI3 surfaces, including reconstructions, which was previously not thoroughly characterized.

Findings

The MAI-terminated surface is more stable than PbI2-terminated.

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

Surface states originate from the conduction band but do not create new gap states.

Abstract

We present a detailed first-principles analysis of the (001) surface of methylammonium lead triiodide (MAPbI3). With density-functional theory we investigate the atomic and electronic structure of the tetragonal (I4cm) phase of MAPbI3. We analysed surfaces models with MAI- (MAI-T) and PbI2-terminations(PbI2-T). For both terminations, we studied the clean-surface and a series of surface reconstructions. We find that the clean MAI-T model is more stable than its PbI2-T counterpart. For the MAI termination,reconstructions with added or removed units of nonpolar MAI and PbI2 are most stable. The corresponding band structures reveal surface states originating from the conduction band. Despite the presence of such additional surface states, our stable reconstructed surface models do not introduce new states within the band gap.