Surface modification of TiO2 photoanodes with In3+ using a simple soaking technique for enhancing the efficiency of dye-sensitized solar cells

[Display omitted] •Modification of TiO2 semiconductor is done using surface doping of In3+.•Decay analysis revealed prolonged charge carrier lifetimes of In-doped cells.•Stability test revealed only a decrease of 90 % PCE after 200 h.•An improvement of 17.9 % PCE in surface-doped cells. Indium-doped TiO2 photoanode for dye-sensitized solar cells are prepared using a simple surface-doping technique by soaking the TiO2 film in acidic In3+ solution at 70 °C for 30, 45 and 60 min followed by sintering at 450 °C. Structural characterization of In-doped TiO2 films by SEM, TEM, EDX, XRD and Raman spectroscopy revealed the successful attachment of Indium to the surface of TiO2 and that the amount of In dopant is proportional to the soaking time. The PCE of the devices fabricated from In-doped TiO2 with a soaking time of 30 min produced an increase of 18.0 % compared to the undoped cells. Charge extraction analysis at open-circuit revealed that surface-doping with indium shifts TiO2 band edge downward. However, the increase in VOC was found as the net effect of negative movement of CB and retarded recombination caused by TiO2 surface passivation via the In dopant.