Growth, structure, optical and optoelectrical characterizations of the Cu_2NiSnS_4 thin films synthesized by spray pyrolysis technique

摘要

Earth-abundant Kesterite materials are very important to fabricate low-cost solar cells. Here, good quality Cu2NiSnS4 (CNSS) thin films were successively manufactured on a glass substrate at 350 degrees C using a simple spray pyrolysis system. The structural characterization of the sprayed Cu2NiSnS4 thin films was examined by the FE-SEM and XRD techniques. X-ray diffraction patterns indicate that the sprayed Cu2NiSnS4 films are single phase and having polycrystalline structure. The elemental composition analysis of the sprayed Cu2NiSnS4 thin films confirmed that the Cu2NiSnS4 film is near stoichiometric in compound. Our optical observations indicate that the refractive index (n) of the sprayed Cu2NiSnS4 films was increased by increasing the film thickness. Moreover, the sprayed Cu2NiSnS4 films exhibit a direct optical transition and the magnitudes of the energy gap have been decreased from 1.28 to 1.14eV with the increase of thickness. The optoelectrical parameters of the Cu2NiSnS4 films, like optical conductivity, optical mobility, optical resistivity, optical carrier concentration and relaxation time were estimated with different thickness. Additionally, the nonlinear optical parameters of the Cu2NiSnS4 films were estimated. The fabricated CNSS-Si heterojunction achieved a conversion efficiency of 11.34%.