Formation of 1-D/3-D Fused Perovskite for Efficient and Moisture Stable Solar Cells

Various organic cations (e.g., methylammonium (MA+), butylammonium (BA+), formamidinium (FA+), etc.) have been studied and used in organometallic halide perovskite solar cells (PSCs). Most of the currently used organic cations are protic in nature, which can induce acid–base reactions and, thus, lead to degradation of the perovskites. So far, the role of aprotic cations in PSCs has not been studied much. In the present study, two aprotic cations, namely, trimethylsulfonium (TMS+) and trimethylsulfoxonium (TMSO+), are introduced into lead-based PSCs to form one-dimensional/three-dimensional (TMSPbI3)x(MAPbI3)100-x and (TMSOPbI3)x(MAPbI3)100-x perovskite structures, respectively. This is shown to provide enhanced performance and moisture resistance, thus, increasing the stability and lifespan of the PSCs. The power conversion efficiencies of the (TMSPbI3)x(MAPbI3)100-x and (TMSOPbI3)x(MAPbI3)100-x devices are found to be 19.34 and 19.94%, respectively, compared to 17.11% for the pristine MAPbI3 PSC, along with enhanced open-circuit voltages (VOC) of 1.14 and 1.12 V, respectively, compared to 1.07 V for the pristine MAPbI3 PSC. Furthermore, the effects of TMS+ and TMSO+ upon the perovskite structure, absorption, recombination, and film morphology are discussed in detail. The results of this study will be helpful in the exploration of sulfur-based cations for the development of more stable PSCs.