Three-junction solar cell

Claim 1

A monolithic photovoltaic cell comprising: an upper surface layer adapted for entrance of exciting light, three semiconductive layers positioned sequentially with respect to a position starting from said upper surface layer, namely an upper layer, a middle layer, and a lower layer, within each of said semiconductive layers, a photovoltaic junction, thus providing upper, middle, and lower junctions, said upper junction having a first polarity with respect to said upper surface, said middle and lower junctions having a second polarity opposite to that of said upper junction, a conductive substrate beneath said lower layer, a conductive electrode connected to said substrate, a light-permeable electrode attached to the upper surface of said upper surface layer, a high gap transparent layer between said middle layer and said lower layer, a first high conductivity layer between said middle layer and said high-gap transparent layer, an aperture through said upper, middle, first high conductivity, and transparent layers, said aperture having stepped sides exposing a portion of the upper surfaces of said middle layer, said first high conductivity layer, and said lower layer, a first metallic conductor in said aperture in ohmic contact with the top of said bottom layer and in overlapping contact with the top of said first high conductivity layer, a second metallic conductor in said aperture insulated from said first conductor and in contact with the upper surface of said middle layer, and means for external electrical connections to said substrate connected electrode, said light permeable electrode, and said second conductor.