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) that lately exceeds 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. The hybrid perovskites are naturally vulnerable to water molecules, which can induce decomposition of perovskite photoactive chemicals such as MAPbI3, FAPbI3. Therefore, to achieve the commercial-level long-term PSC stability, the adsorption and infiltration of water into perovskite films must be minimized. Herein, it is demonstrated that polydimethylsiloxane (PDMS) introduced simultaneously during perovskite spin-coating is highly beneficial to passivate perovskite grains and adjacent grain boundaries (GBs). It not only promotes the formation of lead oxide (PbO) bondings that prevent a water-perovskite reaction but contributes to reducing a Pb defect density related to trap-assisted recombinations. 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 of 5000 h under 70 % relative humidity. These results will pave the way for developing commercial perovskite optoelectronic devices.