Ammonium Thiocyanate-Passivated Quasi-Two-Dimensional Dion Jacobson Perovskite Solar Cells for Improved Efficiency and Stability

Quasi-two-dimensional (quasi-2D) Dion Jacobson (D-J) layered perovskites have recently emerged as attractive photovoltaic materials due to their out-of-plane charge conduction and superior environmental stability. However, their power conversion efficiency (PCE) still needs to be optimized before these perovskites become competitive with their three-dimensional counterpart. Here, we report D-J phase quasi-2D (XDA)(MA)3(Pb)4(I)13 perovskites processed with an ammonium thiocyanate (NH4SCN) additive, showing a stabilized PCE of 17.05% which is one of the highest reported PCEs for a D-J phase quasi-2D perovskite. The NH4SCN additive modification leads to the optimum phase distribution, enlarged grain size, and improved crystallinity. Moreover, increased charge transport and reduced defect density was confirmed in the passivated perovskite. The unencapsulated device retained 80% of its initial PCE after 1000 h of storage under 50% relative humidity and 75% of its initial PCE in 200 h of storage under 85 °C of thermal stress. The synergistic use of NH4SCN with a di-ammonium cation in a quasi-2D perovskite offers new opportunities for the development of highly efficient perovskite solar cells with long-term operational stability.