Patent ID: 7659474

Claim:
A solar cell array having at least one solar cell comprising a photovoltaic structure having a sun-facing front face and a back face, a first photovoltaic cell layer disposed between the front face and the back face, and having an active region; and an isotype heterojunction diode having a second photovoltaic cell layer; wherein the isotype heterojunction diode is connected in electrical parallel with the active region of the first photovoltaic structure and the photovoltaic cell layer of the photovoltaic structure is physically separated from the second photovoltaic cell layer of the isotype heterojunction diode; the isotype heterojunction diode includes a semiconductor layer disposed between a first heterojunction and a second heterojunction; and wherein the semiconductor layer has a continuously graded bandgap that increases moving from the first heterojunction to the second heterojunction so that current flow in the heterojunction diode is asymmetric.