Concentrated Sunlight for Accelerated Stability Studies of Perovskite Solar Cells

Perovskite solar cells exhibited certified power conversion efficiency (PCE) which already approached 22%, but to be considered for large-scale commercial applications these cells have to be stable under operating conditions including exposure to sunlight, heat and electric bias. Here we present stability studies using concentrated sunlight, which allows rapid screening of the degradation parameters in the cells. Specifically, accelerated degradation studies to determine factors affecting degradation at different bias conditions were performed.

Our experimental methodology allows independent control of sunlight intensity, the sample temperature, and environment during the exposure. Experiments revealed that IR filtering can reduce the degradation by reducing the temperature. Stress testing of perovskite solar cells showed that faster degradation was found for cells held at SC under concentrated sunlight and on the initial stage of outdoor exposure. However, cells kept at short circuit (SC) showed better long-term stability compared to cells kept at open circuit (OC) upon real operational conditions. We also found that intensity was more important than the dose for cells degradation at SC conditions, while dose was the determining factor at OC. This indicates that different degradation mechanisms are dominant at different degradation stages and under different bias conditions and that nano-scale understanding of degradation mechanisms is required to suggest ways to increase the device lifetime.