Study on optoelectronic properties of CuInSe2/CuInSSe films and PN junctions

Abstract

CuInSe2 (CIS) is a semiconductor with a direct bandgap of about 1.04 eV. Its potential applications in the field of flexible thin-film solar cells are vast and promising. Improving cell performance through the sulfidation of the CIS absorber layer is a vital method. Furthermore, the bandgap can be adjusted through ideal element doping and interfacial state recombination can be decreased. In this study, the mixed source vacuum evaporation is used to prepare CIS, CuInS1.5Se0.5 and CuInS0.5Se1.5 films, followed by annealing under N2, S, and Se atmospheres. Subsequently, Mo/CIS/CdS PN junction and Mo/CuInSxSe2-x (x = 0.5 or 1.5)/CdS PN junctions are fabricated. The results demonstrate that Se-annealing of CIS films reduces hetero-phase formation, improves crystallization quality and yields high intensities of transmittance and reflectance. S-annealing of CISSe films results in enhanced intensities of transmittance and reflectance. The intensities of the primary XRD peaks of CuInS0.5Se1.5 film are greater than those of the CuInS1.5Se0.5 film. The morphologies of the CISSe films become flatter and smoother as annealing in S-atmosphere. The CuInS1.5Se0.5 film shows a higher photocurrent compared to the CuInS0.5Se1.5 film, suggesting that a greater proportion of S can enhance photo carrier concentration of CISSe films. Additionally, the carrier transport in S-annealed CuInS0.5Se1.5/CdS PN junction is predominantly governed by tunneling current mechanism, while carrier transports of other PN junctions are regulated by leakage current mechanism.