Bright prospect of using alcohol-soluble Nb₂O₅ as anode buffer layer for efficient polymer solar cells based on fullerene and non-fullerene acceptors

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 Nb₂O₅ interfacial layer with ultra-high transmittance. The ultraviolet photoemission spectroscopy results confirm that Nb₂O₅ 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 Nb₂O₅ 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 Nb₂O₅ 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.