Influence of Grain Size and Interfaces on Photo-Stability of Perovskite Solar Cells

Abstract

We report on the photo-stability of perovskite solar cells prepared using solution growth and vapor phase growth. The cells prepared using solution growth had varying grain sizes achieved by using solvent annealing techniques. The cells deposited using co-evaporation were prepared at varying substrate temperatures. All the cells were exposed for 100 hours to varying degrees of intensity of light inside an environmental chamber filled with high purity nitrogen and thus was devoid of moisture and oxygen. It was found that the cells with larger grains had a significantly lower photo-degradation than cells with smaller grains. It was also found that vapor deposited cells, in general, had less photo-degradation than solution-grown cells with similar grain sizes. The photo-degradation is ascribed to the generation of ions by light during the degradation process. A measurement of ion density reveals that the short circuit current during degradation, and even before degradation, is inversely correlated to the measured ion density. The measurement of degradation at varying light intensities shows a light-induced annealing behavior similar to what is found in a-Si, leading to saturation in photo-degradation. It was also found that the interfaces have a profound influence on photo-degradation, with cells deposited on organic interfaces suffering significantly more degradation than cells deposited on inorganic interfaces.