Effect of Precursor Stoichiometry on the Performance and Stability of MAPbBr3 Photovoltaic Devices

TL;DR

This study investigates how slight variations in precursor solution stoichiometry affect the performance, stability, and defect healing in MAPbBr3 perovskite solar cells, revealing that bromide deficiency can enhance efficiency over time.

Contribution

It provides detailed insights into the impact of precursor stoichiometry on the stability and performance of MAPbBr3 devices, highlighting defect healing mechanisms and stability improvements.

Findings

Bromide-deficient films show more than doubled photoconversion efficiency.

Device shelf-storage performance strongly depends on precursor solution stoichiometry.

Environmental exposure contributes to trap healing in perovskite films.

Abstract

The wide band gap methylammonium lead bromide perovskite is promising for applications in tandem solar cells and light-emitting diodes. Despite its utility, there is only a limited understanding of its reproducibility and stability. Herein, the dependence of the properties, performance, and shelf storage of thin films and devices on minute changes to the precursor solution stoichiometry is examined in detail. Although photovoltaic cells based on these solution changes exhibit similar initial performance, the shelf-storage depends strongly on the precursor solution stoichiometry. While all devices exhibit some degree of healing, the bromide-deficient films show a remarkable improvement, more than doubling in their photoconversion efficiency. Photoluminescence spectroscopy experiments performed under different atmospheres suggest that this increase is due in part to a trap healing mechanism that occurs upon exposure to the environment. Our results highlight the importance of understanding and manipulating defects in lead halide perovskites to produce long-lasting, stable devices.