Multijunction metamorphic solar cell

A multijunction solar cell including a terminal of first polarity and a terminal of second polarity, comprising:

• (a) a semiconductor body including:
• a tandem vertical stack of at least an epitaxial upper solar subcell, first middle solar subcell, second middle solar subcell and bottom solar subcell, the upper subcell having a top contact connected to the terminal of the first polarity, and the bottom solar subcell having a top contact and a bottom contact connected to the terminal of second polarity;
• (b) an epitaxially deposited first lateral conduction interlayer disposed adjacent to and beneath the second solar subcell to provide an electrical contact to the bottom of the second solar sub cell;
• (c) an epitaxially deposited blocking p-n diode or insulating layer disposed adjacent to and beneath the first lateral conduction interlayer;
• and
• (d) an epitaxially deposited second lateral conduction layer disposed adjacent to and beneath the blocking p-n diode or insulating layer, wherein the bottom solar subcell is disposed adjacent to and beneath the second lateral conduction layer which forms an electrical contact to the top contact of the bottom solar subcell.

A method of forming a multijunction solar cell assembly comprising:

• (a) providing an integral semiconductor body including a tandem vertical stack of epitaxially grown subcells including at least an upper solar subcell, a first middle solar subcell, a second middle solar subcell and a bottom solar subcell, the upper subcell having a top contact connected to a terminal of the first polarity, and the bottom solar subcell having a bottom contact;
• an epitaxially deposited first lateral conduction layer disposed adjacent to and beneath the second solar subcell thereby forming a bottom contact to the first middle solar subcell;
• an epitaxially deposited blocking p-n diode or insulating layer disposed adjacent to and beneath the first lateral conduction interlayer of the respective semiconductor region;
• an epitaxially deposited second lateral conduction layer disposed adjacent to and beneath the blocking p-n diode or insulating layer, wherein the bottom solar subcell is disposed adjacent to and beneath the second lateral conduction layer;
• (b) etching from the top surface of the semiconductor body to the first lateral conduction layer to make an electrical contact to the first lateral conduction layer and thereby to the bottom contact to the first middle solar subcell;
• and
• (c) etching from the top surface of the semiconductor body to the second lateral conduction layer to make an electrical contact to the second lateral conduction layer and thereby to the top contact of the bottom solar subcell.