Diversification of photoelectric efficiency on DSSCs assembled according to the change of coating layers of Px-TiO2 films

The most optimal electrodes were fabricated using two types of semiconductor composite, Px-TiO2 (bottom)/anatase TiO2 (top) and anatase TiO2 (bottom)/P-TiO2 (top). The Px-TiO2, containing nanometer-sized P (1.0, 5.0, and 10.0 mol%)-incorporated in TiO2 prepared using a solvothermal method, was used as the working electrode material together TiO2. The photovoltaic efficiency of Px-TiO2 (bottom)/anatase TiO2 (top) dye-sensitized solar cells (DSSCs) was higher than that of double-layers of anatase TiO2-DSSC as determined from photocurrent–voltage (I–V) curves. However, device efficiency was reduced on increasing P content for both types of cell: Px-TiO2 (bottom)/anataseTiO2 (top) and anatase TiO2 (bottom)/Px-TiO2 (top) combined electrode arrays. We attributed this result to the energy levels of reduction (conduction band)/oxidation (valence band), as determined by cyclic voltammetry (CV). As the conduction level of Px-TiO2 was at a lower energy level than that of pure anatase TiO2, electron transfer was only possible on the Px-TiO2 (bottom)/anatase TiO2 (top) electrode, and particularly in the P 1.0 mol% TiO2 (bottom)/TiO2 (top)-DSSC. Recombination was also much slower in P 1.0 mol%-TiO2 (bottom)/TiO2 (top)-based DSSCs than in the pure TiO2-double-layered DSSCs.