An Application of Vanadium Oxide Thin Film as Window Layer in CIGSe Thin Film Solar Cells: A Computational Study

In this simulation study, the SCAPS software is used to analyze the Cu(In, Ga)Se2 (CIGSe) thin film solar cells. The parameters, such as thickness, bandgap, and carrier concentration of CIGSe absorber layer, V<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</inf> buffer window layer and ZnO window layer are investigated to obtain the best device performance. The efficiency of CIGSe thin film solar cells is slightly enhanced by absorbing more photons when the CIGSe thickness increases from 1 to 6µm. The variation of CIGSe bandgap affects all four solar cell parameters, which is directly related to the energy of incident photons. The open circuit voltage and fill factor are dependent on the CIGSe carrier concentration. The optimum values of 3µm, 1.4 eV, and 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">16</sup>cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup>were thickness, bandgap, and carrier concentrations for CIGSe. A very thick layer of window layers can raise the series resistance and a very thin layer can reduce the shunt resistance of the device. Both of these conditions strongly decreased the fill factor and consecutively the efficiency value. The best thicknesses of 100 and 25 nm were observed for V<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</inf> and ZnO materials, respectively. The carrier concentrations for the window layer must be higher compared to the absorber layer for improving the device's performance. The optimum efficiency of 14.58 % is found for CIGSe thin film solar cells after using the best parameters of CIGSe, V<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</inf>, and ZnO. Hence, the SCAPS software is promising for modeling and is imperative to assess the proposed physical structure's practicability and performance.