Indium Tin Oxide Induced Internal Positive Feedback and Indium Ion Transport in Perovskite Solar Cells.

Stability is the most pressing challenge hindering the commercialization of perovskite solar cells (PSCs), and previous efforts focused more on enhancing the resistance of PSCs to external stimulus. Here, we found that the indium tin oxide (ITO) will deteriorate the photovoltaic performance of PSCs through positive feedback cycles. Specifically, the perovskite degradation products will cross the electron transport layer to chemically etch the electrode ITO to generate In, which will migrate upwards into the perovskite film. Then, the reaction that corrodes ITO consumes the decomposition products of perovskite and shifts the balance of the perovskite decomposition reaction, further promoting the degradation and thus falling into a positive feedback cycle. Moreover, the In in the perovskite film was found to accumulate at the upper surface, which would lead to n-type doping of perovskite film to form the energy barrier for interface carrier extraction. Subsequently, the chelating molecule ethylenediaminetetraacetic acid disodium salt (EDTA-2Na) was introduced onto ITO to firmly chelate the In and prevent it from migrating upward, thus breaking this internal positive feedback cycle and significantly enhancing the efficiency and stability of PSCs. This work provides new perspectives for understanding the mechanism of photovoltaic performance loss and ionic transport in PSCs.