Efficient inverted hybrid solar cells using poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) bulk heterojunction as active layers and TiO2/Sb2S3 bilayers as electron transport layers (ETL) have been prepared in ambient air. The microstructural, photoelectronic, and electrochemical characteristics on these cells have been investigated. Photoluminescence measurement indicates that the exciton dissociation in TiO2/Sb2S3 is more effective than that in ITO/Sb2S3 structure. The Nyquist plots obtained from electrochemical impedance spectroscopy implies that charge recombination has been suppressed in TiO2/Sb2S3 with respect to Sb2S3 structure. In addition, the TiO2/Sb2S3 bilayer structure exhibits significantly enhanced external quantum efficiency in the visible region. The cell structure consisting of ITO/TiO2/Sb2S3/P3HT:PCBM/PEDOT:PSS/Ag with the TiO2/Sb2S3 bilayer synthesized under the optimized conditions gains an average efficiency of 3.52%, which is enhanced for similar to 28.5% and similar to 209% referring to the cells only with the TiO2 layer and Sb2S3 layer as the ETL, respectively. 2016 Elsevier Ltd. All rights reserved.