The effect of a MoOx hole-extracting layer on the performance of organic photovoltaic cells based on small molecule planar heterojunctions

We report a significant increase in the open circuit voltage (Voc) and power conversion efficiency in both chloroaluminium phthalocyanine (ClAlPc)/fullerene (C60) and boron subphthalocyanine chloride (SubPc)/C60 organic photovoltaic (OPV) cells with the insertion of a thin molybdenum oxide (MoOx) hole-extracting layer. This improvement was not seen with copper phthalocyanine (CuPc)/C60, and the addition of the MoOx layer leads to reduced device performance for pentacene/C60 cells. Cells containing the MoOx layer demonstrated significantly improved stability compared to the cells deposited on bare indium-tin oxide (ITO). External quantum efficiency (EQE) measurements taken before and after constant AM1.5G illumination for 60 min showed reduced current losses for all cells containing the MoOx layer, especially in spectral regions where the donor layer contributes. We attribute this improvement to the increased stability at the MoOx/donor interface.