Tuning the Properties of the CuAl_(1–X)Fe_XS₂ Thin Film as a Potential Absorber for Solar Cell Application

In this work, we achieve the preparation of nontoxic and earth-abundant chalcopyrite quaternary compound CuAl(1–X)FeXS2 thin films by substituting Al with Fe atoms for photovoltaic application. The present work reports tuning the properties of CuAl(1–X)FeXS2 (X = 0, 0.25, 0.50, 0.75, and 1) thin films using the chemical spray pyrolysis technique. The polycrystalline tetragonal crystal structure of the prepared film is confirmed by X-ray diffraction analysis. The Fe-substituted film shows high optical absorption in the visible region compared to pure CuAlS2. The optical energy band gap of the material decreases from 3.07 eV (X = 0) to 1.39 eV (X = 1) with a linear increase in Fe concentration. The SEM images show the spherical and microflake-like morphological structure. From I–V measurement, a good ohmic response is observed for all the samples. All the films display single semicircle impedance nature, and lower electrical resistivity is obtained for CuAl0.25Fe0.75S2 and CuFeS2 thin films. The photovoltaic performance of CuAl0.25Fe0.75S2 and CuFeS2 solar cells is evaluated, and efficiencies of 3.65 and 2.33%, respectively, are obtained. The above mentioned results confirm that the CuAl0.25Fe0.75S2 composition exhibits good optical, morphological, and electrical properties which have potential application prospect in photovoltaic technology.