Tailoring the Open-Circuit Voltage Deficit of Wide-Band-Gap Perovskite Solar Cells Using Alkyl Chain-Substituted Fullerene Derivatives.

Wide-band-gap (WB) perovskite devices are promising as the top cell of silicon-perovskite tandem devices to boost the efficiency beyond the Shockley-Queisser limit. Here, we tailor the performance parameters of WB mixed-halide perovskite solar cell with long alkyl chain-substituted fullerene derivatives as an electron transport layer (ETL). The device with C ₆₀ -fused N-methylpyrrolidine- meta-dodecyl phenyl (C ₆₀ MC ₁₂ ) demonstrates an enhanced power conversion efficiency of 16.74% with the record open circuit voltage ( V _OC ) of 1.24 V, an increase by 70 mV with concomitant V _OC deficit reduction to 0.47 V. This is achieved by mitigating the recombination loss through the use of highly crystalline C ₆₀ MC ₁₂ film compared to amorphous [6,6]-phenyl-C ₆₁ -butyric acid methyl ester layer. The device analysis reveals the soothing of the defect activities with shallower defect states and passivation of the interface recombination centers for the device with C ₆₀ MC ₁₂ . We ascribe this property to the crystallinity of fullerene derivatives as ETL, which is also important for the optimization of device parameters, besides the band alignment matching of WB perovskite devices.