INVERTED MULTIJUNCTION SOLAR CELLS WITH GROUP IV ALLOYS
A method of manufacturing a solar cell comprising providing a growth substrate; depositing on said growth substrate a sequence of layers of semiconductor material forming a solar cell, including at least one subcell composed of a group IV alloy such as GeSiSn; and removing the semiconductor substrate.
1 . A method of manufacturing a solar cell comprising:
providing a semiconductor growth substrate;
depositing on said semiconductor growth substrate a sequence of layers of group III-V compound semiconductor material to form at least one group III-V subcell;
depositing one or more layers of a group IV alloy on the at least one group III-V subcell to form one or more group IV subcells that have an emitter and/or base layer composed of a group IV alloy; and
removing the semiconductor growth substrate.
2 . A method as defined in claim 1 , wherein the group IV alloy is GeSiSn.
3 . A method as defined in claim 2 , wherein the GeSiSn subcell has a band gap in the range of 0.73 eV to 1.1 eV.
4 . A method as defined in claim 3 , wherein said solar cell is a hybrid solar cell further comprising a subcell composed of germanium deposited over said GeSiSn subcell.
5 . A method as defined in claim 4 , wherein said Ge subcell is lattice matched to said GeSiSn subcell over which said Ge subcell is deposited.
6 . A method as defined in claim 1 , wherein the one or more group IV subcells include a first GeSiSn subcell having a band gap in the range of 0.73 eV to 0.90 eV, and a second GeSiSn subcell having a band gap in the range of 0.90 eV to 1.10 eV.
7 . A method as defined in claim 1 , wherein depositing the sequence of layers of the group III-V compound semiconductor material comprises deposition temperatures of at least 600 ° C.
8 . A method as defined in claim 1 , wherein depositing the one or more layers of the group IV alloy comprises deposition temperatures of at most 400° C.
9 . A method as defined in claim 1 , further comprising applying a bonding layer over the one or more group IV subcells and attaching a surrogate substrate to the bonding layer.
10 . A method as defined in claim 9 , wherein after the surrogate substrate has been attached, the semiconductor growth substrate is removed by grinding, etching, or epitaxial lift-off.
11 . A method as defined in claim 1 , wherein said semiconductor growth substrate is selected from the group consisting of GaAs and Ge.
12 . A method as defined in claim 1 , wherein a junction is formed in the group IV alloy to form a photovoltaic subcell by the diffusion of As and/or P into the group IV alloy layer.
13 . A method as defined in claim 1 , further comprising forming window and BSF layers composed of a group IV alloy adjacent to the one or more group IV subcells.
14 . A method of manufacturing a hybrid solar cell comprising:
providing a semiconductor growth substrate;
depositing on said semiconductor growth substrate a sequence of layers of group III-V compound semiconductor material at a deposition temperature of 600° C. to 700° C. to form one or more group III-V subcells;
depositing one or more layers of GeSiSn at a deposition temperature of 300° C. to 400° C. on the at least one subcell to form one or more GeSiSn subcells that have an emitter and/or base layer composed of GeSiSn;
depositing a layer composed of Ge over the GeSiSn layers;
applying a metal contact layer over said Ge layer;
applying a supporting member directly over said metal contact layer; and
removing the semiconductor growth substrate.
15 . A method as defined in claim 14 , wherein depositing said one or more group III-V subcells comprises forming a first group III-V subcell composed of an InGa(Al)P emitter region and an InGa(Al)P base region and having a first band gap; and forming a second group III-V subcell composed of GaAs, InGaAsP, AlGaAs, or InGaP and having a second band gap.
16 . A method as defined in claim 15 , wherein depositing said one or more GeSiSn subcells comprises forming a GeSiSn subcell having a third band gap.
17 . A method as defined in claim 16 , wherein depositing said Ge layer comprises forming a Ge subcell that is lattice matched to said GeSiSn subcell and has a fourth band gap.
18 . A method as defined in claim 17 , wherein said second band gap is smaller than said first band gap; said third band gap is smaller than said second band gap; and said fourth band gap is smaller than said third band gap.
19 . A hybrid multijunction solar cell comprising:
a first solar subcell composed of InGaP or InGaAlP and having a first band gap;
a second solar subcell composed of GaAs, InGaAsP, AlGaAs, or InGaP and disposed over the first solar subcell having a second band gap smaller than the first band gap and lattice matched to said first solar subcell; and
a third solar subcell having an emitter and/or base layer composed of GeSiSn and disposed over the second solar subcell having a third band gap smaller than the second band gap and lattice matched with respect to the second subcell.
20 . A hybrid multijunction solar cell as defined in claim 19 , further comprising a fourth solar subcell composed of Ge and disposed over and lattice matched to the third solar subcell.