Unraveling UV Stability in Metal Halide Perovskites: From Degradation Mechanisms to Molecular Passivation

TL;DR

This paper investigates the mechanisms of UV-induced degradation in MAPbI3 perovskite solar cells using simulations and experiments, revealing how molecular passivation with BDO improves UV stability and device longevity.

Contribution

It combines real-time TDDFT simulations with experimental validation to elucidate degradation mechanisms and demonstrates the effectiveness of BDO passivation in enhancing UV stability.

Findings

UV accelerates MA+ molecule rotation.

BDO passivation suppresses PbI2 formation.

Passivation improves device stability under UV exposure.

Abstract

Understanding the mechanisms of UV-induced degradation is crucial for enhancing the UV stability of perovskite solar cells. The UV-driven structural dynamics of CH3NH3PbI3 (MAPbI3) are investigated using real-time TDDFT simulations, revealing that under the electron and hole excitation, the distortion of the inorganic framework (PbI) is primarily driven by the electron occupation of Pb-p and I-p antibonding states, whereas in the hole case, it is mainly governed by the direct cooling induced distortion. We also find that UV accelerates the rotation of MA+ molecules. Further, a BDO molecule is introduced as a passivant, which suppresses structural distortions and provides multi-phonon channels to dissipate carrier cooling energy. Experimental results confirm the UV-protective role of BDO, with suppressed PbI2 formation and improved device stability. These results clarify the mechanism of the UV-induced degradation in the MAPbI3 perovskite and further elucidate how passivation molecules enhance UV stability.