Bright prospect of using alcohol-soluble Nb 2 O 5 as anode buffer layer for efficient polymer solar cells based on fullerene and non-fullerene acceptors

Abstract New breakthroughs are expecting to be achieved based on the discovery of novel interfacial materials for polymer solar cells (PSCs). Herein, the simple and facial approach of spin-coating technology with post heat and ultraviolet-ozone treatment is performed on niobium oxalate to prepare Nb 2 O 5 interfacial layer with ultra-high transmittance. The ultraviolet photoemission spectroscopy results confirm that Nb 2 O 5 with a work function of 4.85 eV is suitable for employing as anode buffer layer (ABL). The average power conversion efficiencies (PCEs) of the P3HT:PCBM-based fullerene devices with Nb 2 O 5 ABL reaches to 4.01%, surpassing that (3.69%) of the control devices with ITO/PEDOT:PSS ABL. Further investigations on the PBDB-T:ITIC-based non-fullerene PSCs with Nb 2 O 5 ABL demonstrate that a PCE as high as 8.67% can be reached, which is superior to that of device modified by PEDOT:PSS ABL (8.03%). Namely, 8% efficiency improvement in PSCs based on fullerene and non-fullerene acceptors realized as compared to the control devices with PEDOT:PSS ABL.