Optimization of a High Work Function Solution Processed Vanadium Oxide Hole-Extracting Layer for Small Molecule and Polymer Organic Photovoltaic Cells

High Resolution Image Download MS PowerPoint Slide We report a method of fabricating a high work function, solution processable vanadium oxide (V 2 O x (sol) ) hole-extracting layer. The atmospheric processing conditions of film preparation have a critical influence on the electronic structure and stoichiometry of the V 2 O x (sol), with a direct impact on organic photovoltaic (OPV) cell performance. Combined Kelvin probe (KP) and ultraviolet photoemission spectroscopy (UPS) measurements reveal a high work function, n-type character for the thin films, analogous to previously reported thermally evaporated transition metal oxides. Additional states within the band gap of V 2 O x (sol) are observed in the UPS spectra and are demonstrated using X-ray photoelectron spectroscopy (XPS) to be due to the substoichiometric nature of V 2 O x (sol) . The optimized V 2 O x (sol) layer performance is compared directly to bare indium–tin oxide (ITO), poly(ethyleneoxythiophene):poly(styrenesulfonate) (PEDOT:PSS), and thermally evaporated molybdenum oxide (MoO x ) interfaces in both small molecule/fullerene and polymer/fullerene structures. OPV cells incorporating V 2 O x (sol) are reported to achieve favorable initial cell performance and cell stability attributes.