Enhancing Performance and Uniformity of Perovskite Solar Cells via a Solution-Processed C₇₀ Interlayer for Interface Engineering

Abstract

Although some kinds of semiconductor metal oxides (SMOs) have been applied as electron selective layers (ESLs) for planar perovskite solar cells (PSCs), electron transfer is still limited by low electron mobility and defect film formation of SMO ESLs fabricated via low-temperature solution process. Herein, the C₇₀ interlayer between TiO₂ and (HC(NH₂)₂PbI₃)_x(CH₃NH₃PbCl₃)_1-x is prepared by spin-coating and low-temperature annealing for planar n-i-p PSCs. The resultant TiO₂/C₇₀ ESL shows good surface morphology, efficient electron extraction, and facilitation of high-quality perovskite film formation, which can be attributed to the suitable nanosize and the superior electronic property of C₇₀ molecules. In comparison with pristine TiO₂-based PSCs, the efficiency and hysteresis index are, respectively, enhanced 28% and reduced 76% by adding the C₇₀ interlayer between TiO₂ and perovskite on the basis of statistical data of more than 50 cells. With the main advantages of low-temperature process and optimized interface, the champion efficiency of PSCs on flexible substrates could exceed 12% in contrast with the above 18% on rigid substrate.