Boosting the performance and stability of quasi-two-dimensional tin-based perovskite solar cells using the formamidinium thiocyanate additive

The poor oxidative stability of tin-based perovskites has been an obstacle to their widespread implementation in high-performance solar cells. Herein, quasi-two-dimensional (quasi-2D) tin-based perovskite solar cells are fabricated with significantly improved performance and stability, by introducing an additional formamidinium thiocyanate (FASCN) additive into quasi-2D tin-based perovskites. The incorporation of the FASCN additive greatly prevents quasi-2D tin-based perovskites from oxidation during film formation, through strong chemical interactions with the tin component (Sn2+). Moreover, it results in a coarser perovskite grain and a higher degree of crystallinity in the out-of-plane direction, leading to enhanced optoelectronic performance of quasi-2D tin-based perovskites. The best-performing tin-based perovskite solar cell shows an efficiency of 8.17% under reverse scan with a steady-state efficiency of 7.84% at a maximum power point (MPP), while retaining over 90% of its initial efficiency after 1000 hours in a glovebox filled with nitrogen. These results demonstrate a versatile, yet simple methodology that can be applied to other lead-free perovskites suffering from poor oxidative stability.