Multi Band Gap Cu(In,Ga)(S,Se)<sub>2</sub> Thin Films Deposited by Spray Pyrolysis for High Performance Solar Cell Devices

Abstract

The performance of copper indium gallium disulfoselenide (CIGSSe) solar cells strongly depends on the band bap of absorbing layer of CIGSSe. The device performance can be improved by fabricating multi band gap layer of CIGSSe. However, the fabrication of multi band gap CIGSSe using non-vacuum techniques is challenging. In this study, we fabricated solar cell devices which consisted of multi band gap Cu (In,Ga)(S,Se)2 thin films. The CIGS thin films were prepared by the spray-pyrolysis of aqueous precursor solutions of gallium (gallium chloride; GaCl3), copper (indium chloride; CuCl2), indium (indium chloride; InCl3), and Sulphur (thiourea; (SC(NH2)2) sources on Mo-coated glass substrate. The as-sprayed thin films were then selenized at 500 °C for 10 minutes.After selenization, CIGS films were transformed to Cu (In,Ga)(S,Se)2 (CIGSSe). The CIGS films with different composition were deposited again on top of selenized CIGSSe films and selenization process was repeated, hence multi band gap CIGSSe films were fabricated. The Chemical bath deposition (CBD) process was used to deposit cadmium sulphide (CdS) buffer layer. The solar cell fabricated with the device configuration of glass/Mo/CIGSSe/CdS/i-ZnO/AZO showed a power conversion efficiency of 6.51%.