Enhanced photovoltaic performance and stability of planar perovskite solar cells by introducing dithizone

In the two-step spin-coating method, the crystallization and morphology of PbI2 film are essential for producing highly efficient and stable planar heterojunction (PHJ) perovskite solar cells. In this work, the dithizone (DTZ) molecules were introduced into PbI2 precursor to improve the performance of perovskite films. We found that adding DTZ was an effective method to retard the crystallization of PbI2 film and consequently, produced a high-quality perovskite film with pinhole-free, smoother, and fewer defects surface. Most importantly, the presence of residual DTZ in wet PbI2 film also assisted DMSO to slow down the growth of perovskite grains. By tuning the concentration of DTZ, the power conversion efficiency of the best performed cell has increased to 20.66% with negligible photocurrent hysteresis. Meanwhile, the best DTZ device offer an excellent stability, which retained 97% of the initial PCE after storage in the dark for approximately 24 days. We expect this controlled crystallization method could be further explored and provides a useful strategy to improve the performance of perovskite solar cells.