New strategy to overcome the instability that could speed up the commercialization of perovskite solar cells

Current efficiency of perovskite solar cells has reached 23.7%, which is comparable with silicon solar cells. However commercial development is seriously hindered by the instability of the perovskite, especially under moisture conditions. Therefore it is crucial to gain clear understanding of the mechanism of degradation of organic-inorganic perovskite in order to achieve stable perovskite devices. In this paper, the formation and the degradation of perovskite film on different charge transport layers such as a compact TiO2 layer, compact ZnO layer, and ZnO foil, Si nanowires, and porous Si are studied. In addition, density functional theory studies are carried out to better understand the interaction between the perovskite film and substrates. Experimental and theoretical results are combined to draw more reliable conclusion regarding the degradation mechanism. Most notably, the investigations show that the interaction between the iodine (I) atom in the perovskite layer and substrate determine the stability of perovskite cells. As a result, Si has minimum interaction with I atoms and shows maximum stability, while perovskite film degrades on TiO2 film almost immediately