Four Junction Inverted Metamorphic Multijunction Solar Cell with a Single Metamorphic Layer

Abstract

A multijunction solar cell including an upper first solar subcell having a first band gap; a second solar subcell adjacent to the first solar subcell and having a second band gap smaller than the first band gap; a graded interlayer adjacent to the second solar subcell; the first graded interlayer having a third band gap greater than the second band gap; and a third solar subcell adjacent to the graded interlayer, the third subcell having 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 lower fourth solar subcell is provided adjacent to the third subcell and lattice matched thereto, the lower fourth subcell having a fifth band gap smaller than the fourth band gap.

1 . A multifunction solar cell comprising:
 an upper first solar subcell having a first band gap;   a second solar subcell adjacent to said first solar subcell and having a second band gap smaller than said first band gap;   a first graded interlayer adjacent to said second solar subcell; said first graded interlayer having a third band gap greater than said second band gap; and   a third solar subcell adjacent to said first graded interlayer, said third subcell having a fourth band gap smaller than said second band gap such that said third subcell is lattice mismatched with respect to said second subcell.   a second graded interlayer adjacent to said third solar subcell; said second graded interlayer having a fifth band gap greater than said fourth band gap; and   a lower fourth solar subcell adjacent to said second graded interlayer, said lower subcell having a sixth band gap smaller than said fourth band gap such that said fourth subcell is lattice mismatched with respect to said third subcell.   
     
     
         2 . The multijunction solar cell of  claim 1 , wherein the first graded interlayer is compositionally graded to lattice match the second subcell on one side and the third subcell on the other side. 
     
     
         3 . The multijunction solar cell of  claim 1 , wherein the second graded interlayer is compositionally graded to lattice match the third subcell on one side and the bottom fourth subcell on the other side. 
     
     
         4 . The multijunction solar cell as defined in  claim 1 , wherein said first graded interlayer is composed of any of the As, P. N, Sb based III-V compound semiconductors 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, and having a band gap energy greater than that of the second subcell and of the third subcell. 
     
     
         5 . The multijunction solar cell as defined in  claim 1 , wherein said second graded interlayer is composed of any of the As, P. N, Sb based III-V compound semiconductors 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, and having a band gap energy greater than that of the third subcell and of the fourth subcell. 
     
     
         6 . The multijunction solar cell as defined in  claim 1 , wherein the first and second graded interlayers are composed of (In x Ga 1-x ) y Al 1-y As with x and y selected such that the band gap of each interlayer remains constant throughout its thickness. 
     
     
         7 . The multijunction solar cell as defined in  claim 6 , wherein the band gap of the first graded interlayer remains constant at 1.5 eV. 
     
     
         8 . The multijunction solar cell as defined in  claim 6 , wherein the band gap of the second graded interlayer remains constant at 1.1 eV. 
     
     
         9 . The multijunction solar cell as defined in  claim 1 , wherein the upper subcell is composed of an InGaP emitter layer and an InGaP base layer, the second subcell is composed of InGaP emitter layer and a GaAs base layer, the third subcell is composed of an InGaP emitter layer and an InGaAs base layer, and the bottom fourth subcell is composed of an InGaAs base layer and an InGaAs emitter layer lattice matched to the base. 
     
     
         10 . The multijunction solar cell as defined in  claim 1 , wherein the lower fourth subcell has a band gap in the range of approximately 0.6 to 0.8 eV, the third subcell has a band gap in the range of approximately 0.9 to 1.1 eV, the second subcell has a band gap in the range of approximately 1.35 to 1.45 eV and the upper subcell has a band gap in the range of 1.8 to 2.1 eV. 
     
     
         11 . A method of manufacturing a solar cell comprising:
 providing a first substrate;   forming an upper first solar subcell having a first band gap on said first substrate;   forming a second solar subcell adjacent to said first solar subcell and having a second band gap smaller than said first band gap;   forming a first graded interlayer adjacent to said second solar subcell; said first graded interlayer having a third band gap greater than said second band gap;   forming a third solar subcell adjacent to said first graded interlayer, said third subcell having a fourth band gap smaller than said second band gap such that said third subcell is lattice mismatched with respect to said second subcell;   forming a second graded interlayer adjacent to said third solar subcell; said second graded interlayer having a fifth band gap greater than said fourth band gap;   forming a lower fourth solar subcell adjacent to said second graded interlayer, said lower subcell having a sixth band gap smaller than said fourth band gap such that said fourth subcell is lattice mismatched with respect to said third subcell;   mounting a surrogate substrate on top of fourth solar subcell; and   removing the first substrate.   
     
     
         12 . A method as defined in  claim 11 , wherein the lower fourth subcell has a band gap in the range of 0.6 to 0.8 eV; the third subcell has a band gap in the range of 0.9 to 1.1 eV, the second subcell has a band gap in the range of 1.35 to 1.45 eV, and the first subcell has a band gap in the range of 1.8 to 2.1 eV. 
     
     
         13 . A method as defined in  claim 11 , wherein the first substrate is composed of gallium arsenide or germanium, and the surrogate substrate is composed of sapphire, GaAs, Ge or Si. 
     
     
         14 . A method as defined in  claim 11 , wherein the first graded interlayer is compositionally graded to lattice match the second subcell on one side and the third subcell on the other side, and the second graded interlayer is compositionally graded to lattice match the third subcell on one side and the bottom fourth subcell on the other side. 
     
     
         15 . A method as defined in  claim 11 , wherein said first graded interlayer is composed of any of the As, P. N, Sb based III-V compound semiconductors 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, and having a band gap energy greater than that of the second subcell and of the third subcell. 
     
     
         16 . A method as defined in  claim 11 , wherein said second graded interlayer is composed of any of the As, P. N, Sb based III-V compound semiconductors 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, and having a band gap energy greater than that of the third subcell and of the fourth subcell. 
     
     
         17 . A method as defined in  claim 11 , wherein the first and second graded interlayers are composed of (In x Ga 1-x ) y Al 1-y As with x and y selected such that the band gap of each interlayer remains constant throughout its thickness. 
     
     
         18 . A method as defined in  claim 11 , wherein the band gap of the first graded interlayer remains constant at 1.5 eV, and the band gap of the second graded interlayer remains constant at 1.1 eV. 
     
     
         19 . A method as defined in  claim 11 , wherein the first subcell is composed of and InGaP emitter layer and an InGaP base layer, the second subcell is composed of InGaP emitter layer and a GaAs base layer, the third subcell is composed of an InGaP emitter layer and an InGaAs base layer, and the bottom fourth subcell is composed of an InGaAs base layer and an InGaAs emitter layer lattice matched to the base layer. 
     
     
         20 . A method of manufacturing a solar cell comprising:
 providing a first substrate;   depositing on a first substrate a first sequence of layers of semiconductor material forming a first and second solar cells;   depositing on said first and second solar cells a first grading interlayer;   depositing on said first grading interlayer a second sequence of layers of semiconductor material including a second grading interlayer and third and fourth solar cells;   mounting and bonding a surrogate substrate on top of the sequence of layers; and   removing the first substrate.