Enhanced long-term stability of perovskite solar cells by passivating grain boundary with polydimethylsiloxane (PDMS)

Organic-inorganic hybrid perovskite solar cells (PSCs) have attracted considerable attention due to their superior power conversion efficiency (PCE), which has recently exceeded 22%. However, some issues remain regarding their use in real-life environments, with the most pressing matter being their long-term stability under humid conditions. Hybrid perovskites are naturally vulnerable to water molecules, which can induce the decomposition of perovskite photoactive chemicals such as MAPbI₃ and FAPbI₃. Therefore, to achieve commercial-level long-term PSC stability, the adsorption and infiltration of water into the perovskite films must be minimized. Herein, it is demonstrated that polydimethylsiloxane (PDMS) introduced simultaneously during perovskite spin-coating is highly beneficial to passivate the perovskite grains and adjacent grain boundaries (GBs). This not only promotes the formation of lead oxide (PbO) bonds that prevent a water-perovskite reaction, but also contributes to reducing the Pb defect density related to trap-assisted recombination. The photovoltaic performance of the prepared PDMS-passivated PSC is notably enhanced compared to a reference PSC (without PDMS), and surprisingly, more than 90% of the initial PCE (∼15%) is sustained after laboratory storage for 5000 h under 70% relative humidity. These results will pave the way for developing commercial perovskite optoelectronic devices.