A practical tandem structure with a semitransparent mesh-structured Cu2S counter electrode sandwiched between two TiO2 photoelectrodes has been designed for quantum dot-sensitized solar cells (QDSCs). The mesh-structured Cu2S counter electrode exhibits high catalytic activity for polysulfide electrolyte. CdS/CdSe quantum dot-sensitized TiO2 films have been applied as both top and bottom photoelectrodes to testify the effectiveness of the tandem structure. The influence of the TiO2 film thickness on the performance of the tandem cell has been systematically studied. The optimized tandem QDSC shows an improved photocurrent and 12-percent increase of efficiency over the top cell with a 4.7 mu m thick top cell and an 11.0 mu m thick bottom cell, presenting a new effective approach towards highly efficient QDSCs. (C) 2012 Elsevier Ltd. All rights reserved.