Effect of homojunction morphology on Fe-doped CNTS solar cells for improving the photoconversion efficiency

Here, we have synthesized Fe-doped Cu₂NiSnS₄ (CNTS) thin film solar cells by thermal evaporation method. Our aim is to create a homojunction solar cell by manipulating the conductivity type of CNTS thin film by dopant Fe. The synthesized CNTS and Fe-doped CNTS were subjected to structural, optical, morphological, and electrical studies. From the XRD analysis, it is seen that the synthesized thin film possesses a cubic structure, and Raman analysis revealed the presence of the CNTS phase. From UV analysis, we found that the incorporation of the dopant Fe into CNTS thin film induced sp-d interaction that resulted in a decrease in bandgap from 1.80 to 1.39 eV and also leading to a change in conductivity type from N-type to P-type due to a shift in the fermi level which is revealed by Mott Schottky plot. Moreover, the doped CNTS thin film shows comparatively lesser Urbach energy, which indicates that the doped CNTS thin film is less prone to band tailing. From the TEM-SEAD pattern, the hkl parameters were found, which are identical to the XRD analysis. The elemental states of the quaternary compound were found using XPS. The fabricated Fe-doped CNTS solar cells resulted in increased charge carrier concentration from 1.53 × 10¹⁶ to 9.02 × 10¹⁶ m⁻³. The short circuit current increased from 8.5 mAcm⁻² to 14.0 mAcm⁻², and the photoconversion efficiency increased from 2.6 to 4.8%.