Over 25% efficiency and stable bromine-free RbCsFAMA-based quadruple cation perovskite solar cells enabled by an aromatic zwitterion

Abstract

RbCsFAMA-based multi-cation perovskites with a narrow bandgap and high lattice stability show great promise for achieving high performance perovskite solar cells (PSCs). Herein, an aromatic zwitterion of 1-(3-sulfopropyl)pyridinium hydroxide inner salt (SPHI) is introduced into perovskite ink to regulate the crystal growth of bromine-free RbCsFAMA quadruple cation perovskite. The SPHI modulated perovskite film shows significantly improved film quality with increased photoluminescence lifetime from 1110 ns to 1700 ns. Moreover, the sulfonic group and pyridine N⁺ in SPHI synergistically passivate the charged defects in the perovskite film through coordination and electrostatic interaction, which greatly depresses the non-radiative recombination of charge carriers and reduces the open-circuit voltage (V_OC) deficit, resulting in a minimum V_OC loss of 0.36 V. Excitedly, the champion devices yield record efficiencies of 25.01% (certified 24.60%) and 23.40% (certified 22.97%) for RbCsFAMA-based PSCs with aperture areas of 0.09 cm² and 1 cm², respectively, showing great upscaling potential. Unencapsulated devices also demonstrate excellent long-term operational stability. This work provides an avenue for regulating multi-cation light-absorbers to further improve the efficiency and stability of PSCs.