A hydrophobic organic spacer cation for improving moisture resistance and efficiency in mixed-dimensional perovskite solar cells

Abstract

Mixed-dimensional perovskite structures containing two-dimensional (2D) bulky organic cations offer enhanced stability but suffer from lower efficiency compared to their three-dimensional (3D) counterparts. To overcome the stability limitations while maintaining high efficiency, we introduce a hydrophobic sulfoxonium cation for mixed-dimensional perovskite solar cells (MxD-PSCs). Herein, we employ a novel triple organic cation comprising methylammonium iodide (MAI), formamidinium iodide (FAI), and trimethylsulfoxonium chloride (TMSCl) to formulate MAFA(TMS)_xPbI_3−xCl_x perovskites. The incorporation of TMSCl enhances moisture resistance due to its superior hydrophobicity, while also improving charge transfer and reducing non-radiative recombination as confirmed by optical, morphological, and electrical characterizations. The optimized MxD-PSCs achieve a remarkable power conversion efficiency (PCE) of 21.43%, V_OC of 1.10 V, and J_SC of 24.82 mA cm⁻², with FF being enhanced to 78.5% under one-sun illumination (AM 1.5G). Moreover, optimized MxD-PSCs also perform exceptionally with a PCE of 34.18% under indoor lighting (1000 lux). Furthermore, the devices exhibit outstanding stability, retaining 85% of their initial efficiency after 90 days in an inert environment and 84% after 1000 hours under ambient conditions. These findings highlight the potential of the TMSCl cation for enhancing both the stability and PCE of MxD-PSCs, offering a promising pathway for the development of long-lasting and high-performance PSCs.