Abstract
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•Cd and La are co-doped into TiO2 by sol-gel method.•La dopant modulates particle size to enhance dye adsorption.•Cd dopant causes decrease in band gap of TiO2 and creates trap sites.•Only small amount of Cd dopant required for the favorable decrease in band gap.•24% of efficiency increment for 0.1mol% Cd-La TiO2 compared to pure TiO2.
This work report, for the first time, the co-doping of mesoporous TiO2 with Cd2+ and La3+ cations for improved performance of dye-sensitized solar cells (DSSCs). Cd2+ ions modify the TiO2 lattice interstitially and lower the band gap enabling better electron injection. La3+ ions, having a larger ionic radius compared to that of Ti4+ ions, occupy interstitial sites and modulate particle size which increase surface area, hence the dye adsorption. The result demonstrates that DSSC employed with 0.1mol% Cd-La co-doped TiO2 anode an increase in power conversion efficiency of 24% compared to DSSC with pure TiO2 anode. The doping concentration has to remain low as not to completely transform the morphology of TiO2 and to decrease the number of oxygen vacancies forming trap sites for recombination. The selection of ionic radius of dopants is significant as they can modify the TiO2 lattice either by substitution or interstitial of titanium ions.