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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