Interfacial engineering via inserting functionalized water-soluble fullerene derivative interlayers for enhancing the performance of perovskite solar cells

For n-i-p type perovskite solar cells (Pero-SCs), one of the limitations which hinder the improvement of device performance is the extremely low electrical conductivity of the TiO2 electron transport layer (ETL). Herein, two novel functionalized water-soluble fullerene derivatives C60O similar to 18(OH)(similar to 10)(NH2)(similar to 8) (f-C-60) and C70O similar to 18(OH)(similar to 10)(NH2)(similar to 10) (f-C-70) were prepared and utilized as buffer layers between ITO and a vacuum-deposited fullerene C60 ETL in Pero-SCs. After inserting f-C-60 and f-C-70 layers, the Pero-SCs showed an enhanced crystallinity of the perovskite film, more efficient charge transport, reduced recombination and a decreased charge-transport resistance. Therefore, a summit power conversion efficiency (PCE) of 16.97% was achieved for the device with the f-C-60/C-60 ETL, which was similar to 24% higher than that of the control device (13.71%). The PCE of the Pero-SC based on the f-C-70/C-60 ETL also exhibited a 16% enhancement. This work demonstrated the great potential of f-C-60 and f-C-70 for application as ETLs in Pero-SCs.