Enhancing efficiency and stability of inverted structure perovskite solar cells with fullerene C₆₀ doped PC₆₁BM electron transport layer

[6, 6]-phenyl C₆₁butyric acid methyl ester (PC₆₁BM) is a common fullerene derivative widely employed as an electron transport layer in inverted perovskite solar cells. However, major challenges such as interfacial recombination, current leakage and low mobility results in poor photovoltaic performance and stability for PC₆₁BM-based devices. To overcome these issues, we demonstrated, for the first time, doping of the PC₆₁BM with fullerene C₆₀ to tailor the properties of the PC₆₁BM. This doping approach helped to realize superior power conversion efficiency of perovskite solar cell with 17.46% versus pristine device with 14.20%. The C₆₀ doped PC₆₁BM reinforced the surface morphology of the PC₆₁BM layer with reduced roughness and better coverage, up-shift of Fermi Level, higher electrical conductivity, higher maximum charge carrier generation rate, and higher charge collection probability. All these improvements contributed to reduced charge leakage at the interface, reduced charge recombination and promoted efficient charge transfer, transport, and collection. Furthermore, the enhanced hydrophobicity of the C₆₀ doped PC₆₁BM enabled superior ambient device stability compared to the pristine device. This work facilitates a simple and effective route to tailor perovskite solar cell performance towards higher efficiency and better stability.