TiO2 nanocrystals (NCs) with sizes around 20 nm were synthesized by hydrothermal method in acidic autoclaving pH. The hydrothermally grown TiO2 NCs and P25 TiO2 nanoparticles (NPs) were used in the preparation of two different pastes using different procedures. These pastes with different characteristics were separately deposited on FTO glass plates to form multilayer photoanodes of the dye-sensitized solar cells. The aim of this study was to search how a thin sub-layer of the hydrothermally grown TiO2 NCs in the photoanodes could improve the efficiency of TiO2 P25-based solar cells. The highest efficiency of 6.5% was achieved for a cell with a photoanode composed of one transparent sub-layer of hydrothermally grown TiO2 NCs and two over-layers of P25 NPs. Higher energy conversion efficiencies were also attainable using two transparent sub-layers of hydrothermally grown TiO2 NCs. In this case, an efficiency of 7.2% was achieved for a cell with a photoelectrode made of one over-layer of P25 TiO2 NPs. This could show an increase of about 30% in the efficiency compared to the similar cell with a photoanode made of two layers of hydrothermally grown TiO2 NCs
