Interface engineering for achieving efficient and stable perovskite solar cells by Bphen-fullerene dimer

• We synthesized a novel fullerene dimer. • This dimer has well-matched energy levels with perovskite. • This dimer has high electron mobility. • PSC has high photoelectric conversion efficiency and high stability. The design and synthesis of interface engineering materials with high superficial passivation and electron extraction performance is an effective strategy to improve the efficiency and long-time stability of perovskite solar cells (PSCs). Herein, a novel fullerene dimer, namely, 2C 60 -Bphen, is prepared by Prato reaction with a high yield and is first used to be an interface-modified material for PSCs. To passivate the surface defects of perovskite films and improve the interface contact the interface modification layer was introduced. 2C 60 -Bphen with two carbon cages can reduce the self-polymerization of phenanthroline molecules. The well-matched energy levels between 2C 60 -Bphen and perovskite and the high electron mobility of 2C 60 -Bphen are beneficial to the electron extraction and transportation of efficient PSCs. PSC achieves the highest photoelectric conversion efficiency of 20.24 % when using 2C 60 -Bphen as the interface layer, and it can still maintain 85% efficiency after 500h storage under environmental conditions. These results indicate that 2C 60 -Bphen has the potential to be used as interface material for high-performance PSCs.