Fabrication of Aluminum-Doped Zinc Oxide (AZO) as A Buffer Layer for CZTS Thin Film Solar Cells

This research is prioritized at the creation and analysis of aluminum-doped zinc oxide (AZO) thin films as a buffer layer in Cu₂ZnSnS₄ (CZTS) thin-film solar cells. The driving motivation for this work is to find alternatives to the conventional cadmium-based buffer layers, i.e., CdS, that are non-toxic, earth-abundant, and eco-friendly. AZO is considered to be a suitable candidate because of its desirable optical and electrical characteristics. The CZTS absorber layer, AZO buffer layer and zinc oxide (ZnO) window layer waere fabricated through a spin-coating method. The structural, morphological, optical, and electrical properties of the deposited layers were interpreted using characterization techniques. The crystalline phase was determined and secondary phases were detected using X-ray diffraction (XRD). Field Emission Scanning Electron Microscopy (FESEM) displayed the surface morphology and uniformity of the films to be observed. Ultraviolet-visible (UV-Vis) spectroscopy showed optical transparency to be determined and the band gap to be estimated. Electrochemical Impedance Spectroscopy (EIS) exhibit charge transfer resistance and interfacial properties to be gained. Finally, the electrical performance of the solar cell, such as open-circuit voltage ( V _oc ), short-circuit current density ( J _sc ), fill factor (FF), and power conversion efficiency (PCE), were revealed using current-voltage ( J-V ) analysis. The findings justifies that AZO films exhibited good surface coverage and transparency, and they are found to be adequate for use as buffer layers. Solar cell performance was, however, moderate and requires additional optimization of the fabrication parameters and interface engineering.