Theoretical modeling of amorphous silicon-based alloy p-i-n solar cells

Abstract

We have developed a computer model of amorphous silicon based alloy p‐i‐n solar cells based on the solution of the electron and hole continuity equations, together with Poisson’s equation. This model takes into account the spatial and energy variations of the localized state spectrum, nonuniform doping profiles, and nonuniform optical excitation. Heavily doped p⁺ and n⁺ regions are used as contacts, and these enable us to realistically set up the boundary conditions. Appropriate boron profiles have been added to the intrinsic layer, with the density of states being dependent on the doping concentration. The computed dark and light current–voltage characteristics are in good agreement with experimental data. In particular, our results indicate the importance of residual boron doping in the intrinsic layer for cells illuminated through the n⁺ layer, and show that for optimized p‐i‐n devices carrier back diffusion is not a significant effect and that the open circuit voltage is determined by the recombination current.