The stability of the hole transport layer (HTL) in inverted organic photovoltaic cells is of great interest because the conventional HTL material, PEDOT:PSS, shows limited stability. In this work, solution processed vanadium pentoxide (V2O5) was adopted as the HTL, and the effect of annealing on the properties of the HTL was investigated. The inverted organic photovoltaic cell fabricated with V2O5 and annealed for 5min at 165 °C showed the highest power conversion efficiency (PCE) of 3.92%, which is an enhancement of 16% relative to the cell with PEDOT: PSS (PCE=3.36%). The cell with V2O5 was also found to be more stable than the PEDOT: PSS cell, in which a 51% decrease in PCE was observed after 96 h. In contrast, over the same interval, the V2O5 device maintained a PCE 85% of the original value.