Enhancement of photosensitivity in bismuth doped Cu₂ZnSnS₄thin films

In this paper, the effect of bismuth doping on the structural, morphological, optical and electrical properties of Cu₂ZnSnS₄(CZTS) films has been investigated. The undoped and bismuth doped CZTS films (0, 0.5, 1, 1.5 and 2 mol%) were deposited on glass substrates by solution based method. The XRD result shows a significant improvement in the crystallinity of the films with increase in bismuth concentration. The Raman spectra of the films show the dominant peak at 334 cm^–1corresponding to A₁vibrational mode of CZTS kesterite phase. The FESEM micrographs of the films show an enhancement in the grain size and densification with the addition of bismuth ion concentration. The optical bandgap of the films was found to vary (1.59–1.40 eV) with the doping of bismuth ions. TheI–Vcharacteristics indicate twofold increment in the photoconductivity for the bismuth doped CZTS films under 100 mW/cm²illumination suggesting their potential application in photovoltaic devices. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)