Compound semiconductor solar cell

A compound semiconductor solar cell, comprising:

• a light absorbing layer comprising a first compound semiconductor epitaxial layer that has a first conductive type and a second compound semiconductor epitaxial layer that has a second conductive type and is positioned on an inside surface of the first compound semiconductor epitaxial layer;
• a window layer disposed at a front surface of the second compound semiconductor epitaxial layer;
• a front epitaxial contact layer that that has the second conductive type and is disposed at a front side of the window layer;
• an anti-reflection film that is disposed at the front side of the window layer;
• a first electrode that is positioned on the front epitaxial contact layer;
• a back epitaxial contact layer at least partially positioned on an outside surface of the first compound semiconductor epitaxial layer facing opposite to the inside surface, the back epitaxial contact layer having the first conductive type and an impurity concentration that is greater than an impurity concentration of impurities contained in the first compound semiconductor epitaxial layer;
• and
• a second electrode that is positioned on the back epitaxial contact layer, the second electrode including (i) a plurality of first portions that directly contact the back epitaxial contact layer and form ohmic contact with the back epitaxial contact layer and (ii) a plurality of second portions that directly contact the outside surface of the first compound semiconductor epitaxial layer,
• wherein the plurality of first portions and the plurality of second portions are made of a same material.