Using radiative transfer equation to model absorption by thin Cu(In,Ga)Se₂ solar cells with Lambertian back reflector

We investigate the optical absorption in a thin Cu(In,Ga)Se2 solar cell with a Lambertian white paint beneath a transparent back contact. Although this configuration has been proposed more than 30 years ago, it turns out that rigorous simulation of Maxwell's equations demand powerful numerical calculations. This type of approach is time consuming and does not provide a physical insight in the absorption mechanisms. Here, we use the radiative transfer equation to deal with multiple scattering of the diffuse part of the light. The collimated part is treated accounting for wave effects. Our model is in good agreement with optical measurements.