Influence of substrate temperature on physical properties of MnSbInS4 thin films prepared by a simplified spray pyrolysis technique for photovoltaic applications

Abstract

MnSbInS₄ multi-component semiconductor thin films are prepared by chemical spray pyrolysis on glass substrates at various substrate temperatures ranging from 250-400 °C with a constant spray time (5mins). The structural, morphological, optical and electrical properties of the thin films are investigated through different techniques such as X-ray diffraction (XRD), electron diffraction spectroscopy (EDS), UV-Vis absorption spectroscopy and four probe method. The X-ray spectra reveal that the MnSbInS₄ films are polycrystalline in nature with a cubic spinel structure having (220) plane as the preferred orientation. The energy dispersive analysis by X-ray (EDS) studies confirm the presence of Mn, In, Sb and S in the film grown at a substrate temperature of 250 °C. Optical measurements allow us to determine the absorption coefficient which is as high as (1.22 x 10⁵ cm^-1) at 250 ºC indicating that MnSbInS₄ compound has an absorbing property favorable for applications in solar cell devices. It is interesting to note that the structural homogeneity and crystallinity of the films is improved due to the decrease in absorption coefficient (α) and extinction coefficient (k) with an increase of substrate temperature. The observations from photoluminescence measurements reveal that the photoemission is mainly due to the donar-acceptor pair transitions. Moreover, from the electrical studies, it is observed that the electrical resistivity (ρ ) is strongly affected by substrate temperature and the lowest resistivity (ρ = 4.77 x 10³ Ω m ) is obtained for the film grown at 400 ºC. Stylus profilometer was used to measure the film thickness and the values range between 768 nm (250 °C) to 617 nm (400 °C). This indicates that, as the substrate temperature increases, the thickness of the film decreases. Other important parameters like micro-strain (ε) and dislocation density (δ) which are commonly used to describe the structural analysis are also presented.