Morphology-controlled growth of special nanostructure CuInS2 thin films on an FTO substrate and their application in thin film solar cells

Abstract

Nanostructure CuInS2 (CIS) thin films were grown on FTO conductive glass substrates using a solvothermal method at different thiourea concentrations and different precursor concentrations using precursors of copper (II) chloride dehydrate (CuCl2⋅2H2O), indium (III) nitrate (InNO3⋅2H2O), thiourea (CS(NH2)2), hexadecyl trimethyl ammonium bromide (CTAB), oxalic acid (C2H2O4·2H2O), and ethanol (C2H5OH). The effects of thiourea concentrations and precursor concentrations on the crystallographic structure, composition, morphology, optical properties and growth mechanism of CIS thin films were investigated. Solar cells with a glass/FTO/CIS/CdS/i-ZnO/Al–ZnO/Ag structure were prepared, and the photovoltaic performance of the solar cells was studied. It is found that CIS thin films with different nanostructures can be deposited directly onto FTO glass substrates by varying the concentrations of thiourea or precursors. The formation process and growth mechanism of different nanostructure CIS thin films were discussed. All the CIS films exhibit a well-crystallized single crystal with a chalcopyrite phase structure. The optical band gap is in the range of 1.49–1.55 eV, and the conversion efficiency of the CIS thin film solar cell is 0.21%. Additional work is deserved to fabricate the CIS thin films for high performance photovoltaic device applications.