Highly stable organic solar cells with robust interface using fullerenol as molecular linker

Abstract

This study enhances the long-term stability of organic solar cells (OSCs) by introducing a novel interfacial molecular linker, fullerenol (C₆₀(OH)_x), at the inorganic/organic interface. Using X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR), we confirm that C₆₀(OH)_x can form hydrogen bonds with ZnO (O–H⋯O) and Y6 (O–H⋯F). This interaction significantly enhances the compatibility and charge transport at the inorganic/organic interface, thereby establishing a robust interface. By incorporating C₆₀(OH)_x, the power conversion efficiency (PCE) of PM6:Y6 (binary) and PM6:Y6:PC₇₁BM (ternary) devices increased from 14.41% to 16.09% and from 16.10% to 17.81%, respectively. The binary and ternary ZnO/C₆₀(OH)_x devices retained 80% of their initial PCE (T₈₀ lifetime) after annealing at 65 °C in N₂ for 6187 hours and 6973 hours, respectively. Based on the Arrhenius relationship, the T₈₀ lifetime is estimated to reach approximately 34 600 hours at 25 °C in N₂. Additionally, after 1200 hours of continuous light exposure under AM 1.5G simulated solar light at one-sun intensity in N₂, the binary and ternary ZnO/C₆₀(OH)_x devices retained 88% and 91% of their initial efficiency, respectively. This innovative interfacial molecular linker is set to propel the next generation of photovoltaic technologies forward.