Degradation Kinetics of Inverted Perovskite Solar Cells

TL;DR

This study investigates the degradation mechanisms of different perovskite solar cells under light and oxygen, revealing that mixed-cation perovskites are more stable than methylammonium-based ones, with degradation linked to trap formation.

Contribution

It provides a comparative analysis of degradation kinetics in various perovskite compositions under real-world conditions, highlighting the role of trap formation in efficiency loss.

Findings

Mixed-cation perovskites degrade slower under oxygen exposure.

Degradation linked to trap formation within the perovskite layer.

Mixed-cation devices show higher stability than methylammonium-based cells.

Abstract

We explore the degradation behaviour under continuous illumination and direct oxygen exposure of inverted unencapsulated formamidinium(FA)0.83Cs0.17Pb(I0.8Br0.2)3, CH3NH3PbI3, and CH3NH3PbI3-xClx perovskite solar cells. We continuously test the devices in-situ and in-operando with current-voltage sweeps, transient photocurrent, and transient photovoltage measurements, and find that degradation in the CH3NH3PbI3-xClx solar cells due to oxygen exposure occurs over shorter timescales than FA0.83Cs0.17Pb(I0.8Br0.2)3 mixed-cation devices. We attribute these oxygen-induced losses in the power conversion efficiencies to the formation of electron traps within the perovskite photoactive layer. Our results highlight that the formamidinium-caesium mixed-cation perovskites are much less sensitive to oxygen-induced degradation than the methylammonium-based perovskite cells, and that further improvements in perovskite solar cell stability should focus on the mitigation of trap generation during ageing.