Simple O₂ Plasma-Processed V₂O₅ as an Anode Buffer Layer for High-Performance Polymer Solar Cells

A simple O₂ plasma processing method for preparation of a vanadium oxide (V₂O₅) anode buffer layer on indium tin oxide (ITO)-coated glass for polymer solar cells (PSCs) is reported. The V₂O₅ layer with high transmittance and good electrical and interfacial properties was prepared by spin coating a vanadium­(V) triisopropoxide oxide alcohol solution on ITO and then O₂ plasma treatment for 10 min [V₂O₅ (O₂ plasma)]. PSCs based on P3HT:PC₆₁BM and PBDTTT-C:PC₇₁BM using V₂O₅ (O₂ plasma) as an anode buffer layer show high power conversion efficiencies (PCEs) of 4.47 and 7.54%, respectively, under the illumination of AM 1.5G (100 mW/cm²). Compared to that of the control device with PBDTTT-C:PC₇₁BM as the active layer and PEDOT:PSS (PCE of 6.52%) and thermally annealed V₂O₅ (PCE of 6.27%) as the anode buffer layer, the PCE was improved by 15.6 and 20.2%, respectively, after the introduction of a V₂O₅ (O₂ plasma) anode buffer layer. The improved PCE is ascribed to the greatly improved fill factor and enhanced short-circuit current density of the devices, which benefited from the change in the work function of V₂O₅, a surface with many dangling bonds for better interfacial contact, and the excellent charge transport property of the V₂O₅ (O₂ plasma) layer. The results indicate that an O₂ plasma-processed V₂O₅ film is an efficient and economical anode buffer layer for high-performance PSCs. It also provides an attractive choice for low-cost fabrication of organic electronics.