PHOTON RECYCLING IN THIN-FILM GAAS SOLAR CELLS

Resumo

The highest efficiencies in a single-junction solar cells are obtained with devices based on GaAs. As this material is reaching the limit in material quality, the optimization of the design of the cell becomes more important. In this study we implement a patterning technique to the bottom contact layer of thin-film GaAs solar cells that increases the reflectance of photons to the active layers. Both shallow junction and deep junction devices were evaluated, and the area of the rear side of the cells covered by the contact layer was varied from 100% to 10%. With the patterning, a clear increase in reflectance can be observed for both geometries, but an improved performance was only seen in deep junction devices. For these cells, both the short circuit current and the open circuit voltage increase with the reflectance. Dark curve analysis demonstrated a reduction in the radiative saturation current density, indicating that the observed increase in the open circuit voltage is a result of increased photon recycling.