The origin of higher open-circuit voltage in Zn-doped TiO2 nanoparticle-based dye-sensitized solar cells

Zn-doped anatase TiO(2) nanoparticles are synthesized by a one-step hydrothermal method. Detailed electrochemical measurements are undertaken to investigate the origin of the effect of Zn doping on the performance of dye-sensitized solar cells (DSSCs). It is found that incorporation of Zn(2+) into an anatase lattice elevates the edge of the conduction band (CB) of the photoanodes and the Fermi level is shifted toward the CB edge, which contributes to the improvement in open-circuit voltage (V(OC)). Charge-density plots across the cell voltage further confirm the increase in the CB edge in DSSCs directly. Photocurrent and transient photovoltage measurements are employed to study transport and recombination dynamics. The electron recombination is accelerated at higher voltages close to the CB edge, thus leading to a negative effect on the V(OC).