Enhanced solar energy harvesting using top n-contact GaAs solar cell

•Comparison of top and bottom contact single junction GaAs solar cell performance reported.•Top contact solar cell has higher harvesting power than bottom contact solar cell.•EQE of top contact solar is higher than bottom contact devices.•Short circuit current of 26 mA/cm2 for single junction GaAs solar cell is achieved.

We fabricated single-junction solar cell on molecular beam epitaxially grown p–n junction on n-type gallium arsenide (GaAs) substrate. We used a germanium (Ge)/gold (Au)/nickel (Ni)/Au metal contact from the top side on a highly doped n+ epitaxial layer as well as the bottom side on an n-type GaAs substrate. We observed 10–15% increase in solar cell power when the top contact is used for the n+ GaAs epi layer compared to the bottom side n-type GaAs substrate. Solar cell fill factor, sheet, and shunt resistances are same for both the top and bottom contact type devices. We also observed higher external quantum efficiency (EQE) for top contact devices compared to bottom contact devices. We conclude that to achieve higher power, it is advantageous to use an n-type contact from a highly doped top n+ epitaxial layer rather than a bottom n-type GaAs substrate.