Structural optimization of a Cu(In,Ga)Se2 thin film solar cell using numerical simulation and design of experiment techniques

The structural optimization for a thin film solar cell module based on Cu(In,Ga)Se₂ is investigated through numerical simulation and sequential statistical analyses. First, an equivalent numerical model for solar cells is constructed with an electrical circuit consisting of large area diodes and analysis using finite element analysis (FEA). A good agreement in performance characteristic curves between the developed numerical model and practical solar cells is obtained after performing parameter adjustments. To maximize the light conversion efficiency, an optimization technique using the design of experiment (DOE) of orthogonal arrays is employed. The programmed block diagram is used to calculate electric potentials inside solar cell layers and the associated solar performances. Statistical analysis of variance (ANOVA) and F-test are used to discover the dominant design variables (DVs) which are more important on solar cell performances. The second order regression model which relates dominant DVs with solar cell efficiency is mathematically obtained by the employment of response surface model (RSM) and graphically described by the equipotential contour plots.