Revealing the stability and efficiency enhancement in mixed halide perovskites MAPb(I$_{1-x}$Cl$_x$)$_3$ with ab initio calculations

TL;DR

This study uses ab initio calculations to analyze how adding chloride to mixed halide perovskites improves stability and optoelectronic properties, revealing optimal Cl content for enhanced performance.

Contribution

It provides a detailed theoretical analysis of Cl addition effects on structural and electronic properties of MAPb(I$_{1-x}$Cl$_x$)$_3$, elucidating mechanisms behind stability and efficiency improvements.

Findings

Lattice constants and dielectric constants decrease linearly with Cl content.

Band gaps and exciton binding energies increase quadratically with Cl content.

Optimal Cl content (~7%) minimizes exciton binding energy and alters chemical stability.

Abstract

A little addition of Cl to \ce{MAPbI3} has been reported to improve the material stability as well as light harvesting and carrier conducting properties of organometal trihalide perovskites, the key component of perovskite solar cell (PSC). However, the mechanism of performance enhancement of PSC by Cl addition is still unclear. Here, we apply the efficient virtual crystal approximation method to revealing the effects of Cl addition on the structural, electronic, optical properties and material stability of \ce{MAPb(I_{1-x}Cl_x)3}. Our {\it ab initio} calculations present that as the increase of Cl content cubic lattice constants and static dielectric constants decrease linearly, while band gaps and exciton binding energies increase quadratically. Moreover, we find the minimum of exciton binding energy at the Cl content of 7\%, at which the chemical decomposition reaction changes coincidentally to be from exothermic to endothermic. Interactions among constituents of compound and electronic charge transferring during formation are carefully discussed. This reveals new prospects for understanding and designing of stable, high efficiency PSCs.