Photovoltaic performances of Cu2−xTe sensitizer based on undoped and indium3+-doped TiO2 photoelectrodes and assembled counter electrodes

•Indium doping acts as a trap state mediator to facilitate electron transfer in TiO2.•Cu2S CE induced higher electrocatalytic activity and obtained more faster hole recovery rate.•The main increased Jsc and Voc for carbon and Cu2S CEs, respectively, yielding the best η of 0.73%.•The lower Rct indicated to the suppression in carrier recombination due to In3+ doping and Cu2S CE.

Novel binary Cu2−xTe nanoparticles based on undoped and indium-doped TiO2 photoelectrodes were synthesized using a successive ionic layer adsorption and reaction (SILAR) technique as a sensitizer for liquid-junction solar cells. A larger diameter of TiO2 promoted a narrower energy band gap after indium doping, attributing to yield a broader absorption range of nanoparticle sensitizer due to the increasing amount of Cu2−xTe NPs on TiO2 surface. The atomic percentages showed the stoichiometric formation of Cu2Te incorporated in a Cu2−xTe structure. The best photovoltaic performance with the lower SILAR cycle, i.e., n = 13 was performed after indium doping in both of carbon and Cu2S CEs and revealed that the efficiency of 0.73% under the radiant 100 mW/cm2 (AM 1.5G). The electrochemical impedance spectroscopy (EIS) was used to investigate the electrical properties via effect of material doping and counter electrodes with a lower charge-transfer resistance (Rct) and it was also found that the electron lifetime was improved after the sample doped with indium and assembled with carbon CE.

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