Improving conversion efficiency of co-electrodeposited CuInSe₂ thin film solar cells with substrate and solution heating

As-prepared electrodeposited CuInSe₂ film is amorphous and rough. After CuInSe₂ films growth, cadmium sulfide layers are deposited by chemical bath. The interface between the CuInSe₂ layer and the CdS layer is a p–n junction for high-efficiency solar cells. The CuInSe₂ layer must be defect-free and smooth to make a junction. In this work, CuInSe₂ films with a smooth surface are obtained by heating the substrate and solution, and the solar cell of open circuit voltage is improved from 69 to 371 mV, the fill factor from 26.3 to 52 % and the conversion efficiency from 0.49 to 6.46 %. The structural properties of these selenized films are investigated using X-ray diffraction (XRD). Field-emission scanning electron microscopy images indicate that the ordered copper indium diselenide thin films are entirely filled. XRD results show that the copper indium diselenide thin films are crystalline with highly preferential orientation. Energy-dispersive spectroscopy analysis was used to determine the composition of the films.