Chemical bath composition effect on the properties of electrodeposited CuInSe2 thin films

Highlights: • CIS thin films were grown by electrodeposition technique. • For [Se]/[Cu + In] molar ratio less than 1.3 CIS films have single phase chalcopyrite structure. • For [Se]/[Cu + In] = 1.3 CuSe secondary phase is present. • The optical absorption is due to an allowed direct transition with band gap range between 1.04 and 1.2 eV. -- Abstract: Polycrystalline chalcopyrite CuInSe2 (CIS) thin films were deposited by electrodeposition technique onto ITO coated glass substrates. The used bath solution is formed by dissolution of CuCl2, InCl3, and SeO2 salts in de-ionized water, where the [Se]/[Cu + In] molar ratio is ranged from 0.4 to 1.3. The deposited films have been annealed at 300 °C for 30 min in argon atmosphere. The films structure and surface morphology characterizations were carried out respectively by means of X-ray diffraction method (XRD) and scanning electron microscope (SEM). XRD results indicate that CIS films having single phase chalcopyrite are obtained when the [Se]/[Cu + In] molar ratio is less than 1.3. While, for [Se]/[Cu + In] = 1.3, CuSe secondary phase is present together with CIS chalcopyrite phase. The crystallites were found to have a preferred orientation along (1 1 2) direction. The UV–visible optical transmittance measurements show that films absorption is due to allowed direct transition with a band gap ranged from 1.04 to 1.2 eV