Charge recombination at the electrode/electrolyte interface can be prevented by efficient blocking layers. Here, TiO2 blocking layers have been deposited using atomic layer deposition (ALD) and TiCl4 treatment. The number of TiO2 ALD cycles was optimized for I-/I3- and Fc/Fc(+) electrolytes. The optimized TiO2 ALD films' performance was compared with the TiCl4 treated films. TiCl4 treated films performed better than the ALD deposited films, attributed to reduction of the defects, which act as active sites of recombination. (C) 2015 Elsevier B.V. All rights reserved.