Increased Performance of Thin-film GaAs Solar Cells with Improved Rear Interface Reflectivity

The highest efficiencies in 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 for deep junction cells, both the short circuit current and the open circuit voltage increase with the reflectance. The radiative saturation current density also decreases, indicating increased photon recycling. Detailed model simulations are performed to further evaluate the mechanisms leading to the improved performance of the deep junction design. Based on the same model, the possibilities for further improvements utilizing the deep junction are also identified.