We have investigated the inverted poly (3-hexylthiophene):methano-fullerene [6,6]-phenyl C71-butyric acid methyl ester (P3HT:PC71BM) bulk heterojunction (IBHJ) solar cell with various n-type metal oxide nano particle layers on ITO and MoO3 anode buffer layer underneath Al. The IBHJ solar cell with a tin oxide nano particle layer shows the power conversion efficiency (PCE) of 3.1% and better stability compared to conventional BHJ solar cell. The PCE of this cell decreases by 3% after 2 months in ambient air while the other cells show more degradation. (C) 2011 Elsevier B.V. All rights reserved.