A ZnO/TiO2 composite layer was fabricated on top of a nanoporous TiO2 layer to form a heterostructure bilayer photoanode (P-PZ). The in-situ scattering sites of ZnO were formed inside the assembled photoanode (P-PZ) through the dissolution of ZnO particles caused by soaking in titanium tetrachloride solution. In comparison, the conventional TiO2 photoanodes (2P) and photoanodes with incorporation of the commercial large TiO2 particles (P-PT) were also prepared, and the three photoanodes (2P, P-PT, P-PZ) were all with the thickness of about 14.2 mu m. A light-to-electricity conversion efficiency (eta) of 7.50% was received for the P-PZ-based DSSCs, much higher than that of the DSSCs with 2P (5.34%) and P-PT (5.96%) photoanodes. The superior performance of the DSSC with P-PZ photoanode is mainly attributed to the following factors. (i) The in-situ scattering sites exhibit great light scattering ability, resulting in the great improvement in the short-circuit current density (J(sc)). (ii) The ZnO-coated TiO2 structure shifts the conduction band of TiO2, leading to the great increase in the open circuit voltage (V-oc). (C) 2015 Elsevier Ltd. All rights reserved.