Specific Al mole ratio doping aided flake-like ZnO surface morphology nanostructures film for efficient window layer in CuInS2 photovoltaic cells

Abstract ZnO thin film with flake-like surface morphology has been optimized by Al doping via the home-built chemical spray pyrolysis technique at substrate temperature 250 °C. Then, its performance as an anti-reflecting as well as highly transparent and conducting window layer in CuInS 2 based solid-state solar cell is explored here. The solid-state properties of the pristine and Al-doped ZnO (AZO) thin films have been studied to determine its potential for use in photovoltaic applications. First, it substantiates that the Zn, O and Al atoms are mainly involved for the growth of hexagonal wurtzite crystal structure by EDAX, XPS and XRD studies. All the films exhibit good optical transmittance nearly ∼90–95% in the visible energy region. Further, the 2 wt% AZO film shows low reflection loss in the same region. The decreased electron forbidden gap size is noticed in Al doped ZnO as compared to pure ZnO film. The good electrical parameters i.e., high conductivity (0.26 mho cm −1 ) and low resistivity (3.8 Ω cm) are found in the 2 wt% AZO film. Wettability test confirms the 2 wt% AZO flake-like surface morphology exhibited hydrophobic nature. Eventually, the 2 wt% Al-doped ZnO flake-like morphology thin film utilized as a window layer in CuInS 2 based solid-state solar cell which exhibits a pronounced photocurrent density result in 2.20% power conversion efficiency (PCE) is achieved. This efficiency is superior to all others and 53% higher than that of pristine ZnO window layer based photovoltaic cell.