Electronic Structure and Stability of the CH3NH3PbBr3 (001) Surface

TL;DR

This study uses density functional theory to analyze the surface energetics and electronic properties of CH3NH3PbBr3 perovskite (001) surfaces, revealing stable surface terminations and potential for interface tuning in solar cells.

Contribution

It provides the first detailed comparison of different surface terminations of CH3NH3PbBr3 and their electronic effects relevant for photovoltaic applications.

Findings

CH3NH3Br-terminated surface is more stable than PbBr2-terminated surface.

Surface states near band edges could influence photovoltaic performance.

Differences in electron affinity suggest possibilities for interface engineering.

Abstract

The energetics and the electronic structure of methylammonium lead bromine (CH3NH3PbBr3) perovskite (001) surfaces are studied based on density functional theory. By examining the surface grand potential, we predict that the CH3NH3Br-terminated (001) surface is energetically more favorable than the PbBr2-terminated (001) surface, under thermodynamic equilibrium conditions of bulk CH3NH3PbBr3. The electronic structure of each of these two different surface terminations retains some of the characteristics of the bulk, while new surface states are found near band edges which may affect the photovoltaic performance in the solar cells based on CH3NH3PbBr3. The calculated electron affinity of CH3NH3PbBr3 reveals a sizable difference for the two surface terminations, indicating a possibility of tuning the band offset between the halide perovskite and adjacent electrode with proper interface engineering.