A method of manufacturing an inverted metamorphic multijunction solar cell is disclosed herein. The method includes forming a lattice constant transition material positioned between a first subcell and a second subcell using a metal organic chemical vapor deposition (MOCVD) reactor. The solar cell further includes at least one distributed Bragg reflector (DBR) layer directly adjacent a back surface field (BSF) layer.

The present invention utilizes epitaxial lift-off in which a sacrificial layer is included in the epitaxial growth between the substrate and a thin film III-V compound solar cell. To provide support for the thin film III-V compound solar cell in absence of the substrate, a backing layer is applied to a surface of the thin film III-V compound solar cell before it is separated from the substrate. To separate the thin film III-V compound solar cell from the substrate, the sacrificial layer is removed as part of the epitaxial lift-off. Once the substrate is separated from the thin film III-V compound solar cell, the substrate may then be reused in the formation of another thin film III-V compound solar cell.

Multijunction solar cells are provided having at least four p-n junctions with a rear-side germanium subcell, orientated away from the light, and at least three subcells made of III-V compound semiconductors, disposed above the germanium subcell, the multijunction solar cells having at least one metamorphic buffer layer and at least one wafer-bonded compound and all the layers, which are disposed above the germanium subcell, comprising respectively a light-absorbing emitter- and/or base layer which comprise at least 20% indium, relative to the sum of all the atoms of group III. Furthermore, methods of using of these multijunction solar cells in space are also provided.

A method of manufacturing a solar cell that includes providing a semiconductor growth substrate; depositing on said growth substrate a sequence of layers of semiconductor material forming a solar cell; applying a metal contact layer over said sequence of layers; affixing the adhesive polyimide surface of a permanent supporting substrate directly over said metal contact layer and permanently bonding it thereto by a thermocompressive technique; and removing the semiconductor growth substrate.

Photovoltaics configured to be manufactured without epitaxial processes and methods for such manufacture are provided. Methods utilize bulk semiconducting crystal substrates, such as, for example, GaAs and InP such that epitaxy processes are not required. Nanowire etch and exfoliation processes are used allowing the manufacture of large numbers of photovoltaic cells per substrate wafer (e.g., greater than 100). Photovoltaic cells incorporate electron and hole selective contacts such that epitaxial heterojunctions are avoided during manufacture.

Distributed Bragg reflectors are incorporated into the compositionally graded buffers of metamorphic solar cells, adding functionality to the buffer without adding cost. The reflection aids in collection in subcells that are optically thin due to low diffusion length, high bulk recombination, radiation hardness, partially-absorbing quantum structures, or simply for cost savings. Performance enhancements are demonstrated in GaAs subcells with QWs, which is beneficial when GaAs is not the ideal bandgap.

A multijunction solar cell includes an upper first solar subcell having a first band gap, a second solar subcell having a second band gap smaller than the first band gap, and a first graded interlayer composed of (InxGa1-x)yAl1-yAs adjacent to the second solar subcell. The first graded interlayer has a third band gap greater than the second band gap subject to the constraints of having the in-plane lattice parameter greater or equal to that of the second subcell and less than or equal to that of the third subcell, wherein 0<x<1 and 0<y<1, and x and y are selected such that the band gap of the first graded interlayer remains constant throughout its thickness at 1.5 eV. A third solar subcell is adjacent to the first graded interlayer and has a fourth band gap smaller than the second band gap such that the third subcell is lattice mismatched with respect to the second subcell. A second graded interlayer composed of (InxGa1-x)yAl1-yAs is adjacent to the third solar subcell and has a fifth band gap greater than the fourth band gap subject to the constraints of having the in-plane lattice parameter greater or equal to that of the third subcell and less than or equal to that of the bottom fourth subcell, wherein 0<x<1 and 0<y<1, and x and y are selected such that the band gap of the second graded interlayer remains constant throughout its thickness at 1.1 eV. A lower fourth solar subcell is adjacent to the second graded interlayer and has a sixth band gap smaller than the fourth band gap.

The disclosure describes multi-junction solar cell structures that include two or more graded interlayers.

A method of making a virtual substrate includes providing a donor substrate comprising a single crystal donor layer of a first material over a support substrate, wherein the first material comprises a ternary, quaternary or penternary semiconductor material or a material which is not available in bulk form, bonding the donor substrate to a handle substrate, and separating the donor substrate from the handle substrate such that a single crystal film of the first material remains bonded to the handle substrate.

A multijunction solar cell includes an upper first solar subcell, a second solar subcell adjacent to the first solar subcell, a third solar subcell adjacent to the second solar subcell, and a graded interlayer adjacent to the third solar subcell. The graded interlayer has a band gap that is greater than the band gap of the third solar subcell and is composed of a compositionally step-graded series of (In.sub.xGa.sub.1-x).sub.yAl.sub.1-yAs layers with monotonically changing lattice constant, with x and y having respective values such that the band gap of the graded interlayer remains constant throughout its thickness, and wherein 0<x<1 and 0<y<1. A fourth solar subcell is adjacent to the graded interlayer and is lattice mismatched with respect to the third solar subcell. The graded interlayer provides a transition in lattice constant from the third solar subcell to the fourth solar subcell. A lower fifth solar subcell is adjacent to the fourth solar subcell.