Modeling of Electron Diffusion Length in GaInAsN Solar Cells

This paper seeks to quantify the electron diffusion length in p-type GaInAsN and to understand the performance of GaInAsN cells. The usual modeling is complicated because the electron diffusion length is quite short (often < 0.1 μm) and is usually less than the hole diffusion length. The properties (e.g. absorption and transport) of GaInAsN are both variable and poorly studied, and, because the band gap of GaInAsN is less than the band gap of the substrate, light that is transmitted through the GaInAsN layer may be reflected from the back metallization and make a second pass through the GaInAsN. Layers that are expected to be p-type can sometimes change to n-type, changing the location of the junction and complicating the modeling, but improving the performance of the cell. Internal quantum efficiencies as high as 80% near the GaAs band edge are reported.