Nanocrystalline ZnO and Ga-doped ZnO thin films have been prepared by sol gel spin coating technique. X-ray diffraction results indicated that the grain size of Ga-doped ZnO is smaller than that of ZnO. The EDAX analysis confirmed that Zn, O and Ga elements are present in the samples. HRTEM image shows the formation of ZnO and Ga-doped ZnO nanocrystalline thin films with an average grain size of 22.5 and 12.5 nm. Inverted polymer solar cell containing Ga-doped ZnO as an electron transport layer with device structure ITO/Ga-doped ZnO/poly(3-hexylthiophene) (P3HT):[6,6]-phenyl C-71-butyric acid methyl ester (PC71BM)/MoO3/Al has been fabricated. The power conversion efficiency of inverted polymer solar cell with Ga-doped ZnO is 3.25%, which is higher than that of ZnO (1.96%). (C) 2013 Elsevier Ltd. All rights reserved.