Ion-Migration Inhibitor for Spiro-OMeTAD/Perovskite Contact toward Stable Perovskite Solar Cells

Dopants are utilized to enhance the mobility and optimize energy levels of hole-transporting layers in perovskite solar cells (PSCs), which are crucial to achieving high power conversion efficiencies (PCEs) of normal PSCs. However, the traditional method of doping 2,2′,7,7′-tetrakis(N,N-di(4-methoxyphenyl)amino)-9,9-spirobifluorene (Spiro-OMeTAD) with lithium bis(trifluoromethylsulfonyl)imide (Li-TFSI) can cause inward migration of Li-ions to perovskite, which is one of the main factors affecting the long-term stability of PSCs. In this study, we utilized a multifunctional ion-migration inhibitor at the Spiro-OMeTAD/perovskite interface to control ion migration. As a result, both Spiro-OMeTAD and perovskite were safeguarded and the device's operational stability was enhanced. The optimized devices with 4-methanesulfonyl-benzamidine hydrochloride exhibited an improved PCE of up to 25.3%. Meanwhile, we documented 520-h T90 under continuous 1-sun illumination, 740-h T80 heating at 60 ± 5 °C, and 1000-h T92 at maximum power point tracking at 50 ± 5 °C under continuous 1-sun illumination.