The photoelectrochemistry of transition metal-ion-doped TiO2 nanocrystalline electrodes and higher solar cell conversion efficiency based on Zn2+-doped TiO2 electrode

Metal-ion-doped TiO2 nanoparticles were prepared with hydrothermal method. The change of photocurrents at different electrode potentials and wavelengths of incident light showed two different characteristics for various transition metal-ion-doped TiO2 electrodes. In Zn2+ and Cd2+-doped TiO2 electrodes, a characteristic of n-type semiconductor was observed and the incident photon to conversion efficiency (IPCE) were larger than that of pure TiO2 electrode at the thickness of electrode film of 0.5 μm when the content of doped metal ion was less than 0.5%. The effect of the thickness of films on IPCE was also investigated. The IPCE of pure TiO2 electrode was strongly dependent on the thickness of films. The change tendency of the IPCE for Zn2+-doped TiO2 (0.5% Zn2+) electrodes with its thickness was different from that of pure TiO2. In Fe3+, Co2+, Ni2+, Cr3+ and V5+-doped TiO2 electrodes, a phenomenon of p-n conversion was observed. The difference of photoresponse and the value of photocurrents are dependent on the doping method and concentration of the doped metal ions. The maximum conversion efficiency of RuL2(SCN)2-sensitized Zn2+-doped TiO2 solar cell (1.01%) was larger than that of RuL2(SCN)2-sensitized pure TiO2 solar cell (0.82%) at the same conditions when 0.5 mol · l−1 (CH3)4N · I + 0.05 mol · l−1 I2 in propylene carbonate solution was used as electrolyte.