High efficiency multijunction photovoltaic cells

Abstract

Multijunction photovoltaic cells having at least three subcells are disclosed, in which at least one of the subcells comprises a base layer formed of GaInNAsSb. The GaInNAsSb subcells exhibit high internal quantum efficiencies over a broad range of irradiance energies.

1 . A multijunction photovoltaic cell comprising:
 a (Si,Sn) Ge substrate;   at least three subcells overlying the (Si,Sn)Ge substrate, wherein:
 each of the at least three subcells is lattice matched to each of the other subcells and to the (Si,Sn)Ge substrate; 
 at least one of the subcells comprises a GaInNAsSb subcell comprising a Ga 1-x In x N y As 1-y-z Sb z  base layer, wherein the Ga 1-x In x N y As 1-y-z Sb z  base layer includes: 
 0.075≤x≤0.081, 0.040≤y≤0.051, and 0.010≤z≤0.018, 
 a band gap from 1.111 eV to 1.117 eV, 
 a thickness from 1 μm to 4 μm, 
 a short circuit current density Jsc greater than 9 mA/cm 2 , and 
 an open circuit voltage Voc greater than 0.4 V, 
 wherein the Jsc and the Voc are measured using a 1 sun AM1.5D spectrum at a junction temperature of 25° C. 
   
     
     
         2 . The multijunction photovoltaic cell of  claim 1 , wherein the Ga 1-x In x N y As 1-y-z Sb z  base layer has an internal quantum efficiency greater than 70% at irradiance energies from about 1.27 eV to about 1.38 eV. 
     
     
         3 . The multijunction photovoltaic cell of  claim 1 , wherein the GaInNAsSb subcell is characterized by a Eg/q-Voc equal to or greater than 0.55 V measured using a 1 sun AM1.5D spectrum at a junction temperature of 25° C. 
     
     
         4 . The multijunction photovoltaic cell of  claim 1 , wherein the GaInNAsSb subcell is characterized by a Eg/q-Voc from 0.4 V to 0.7 V measured using a 1 sun AM1.5D spectrum at a junction temperature of 25° C. 
     
     
         5 . The multijunction photovoltaic cell of  claim 1 , wherein the GaInNAsSb subcell is characterized by a compressive strain less than 0.6%. 
     
     
         6 . The multijunction photovoltaic cell of  claim 1 , wherein the GaInNAsSb subcell is characterized by a compressive strain from 0.1% to 0.6%. 
     
     
         7 . The multijunction photovoltaic cell of  claim 1 , wherein the GaInNAsSb subcell has a thickness from 2 μm to 3 μm. 
     
     
         8 . The multijunction photovoltaic cell of  claim 1 , wherein at least two of the subcells comprises a GaInNAsSb subcell. 
     
     
         9 . The multijunction photovoltaic cell of  claim 1 , wherein the GaInNAsSb subcell comprises a window, wherein the window includes (Al)InGaP or (In)GaAs having a thickness from 0 nm to 300 nm. 
     
     
         10 . The multijunction photovoltaic cell of  claim 1 , wherein the GaInNAsSb subcell comprises an emitter, wherein the emitter includes (In)GaAs or a GaInNAsSb alloy having a thickness from 100 nm to 200 nm. 
     
     
         11 . The multijunction photovoltaic cell of  claim 1 , wherein the GaInNAsSb subcell comprises an emitter, wherein the emitter includes InGaAs or a III-AsNV alloy having a thickness from 100 nm to 150 nm. 
     
     
         12 . The multijunction photovoltaic cell of  claim 1 , wherein GaInNAsSb subcell comprises a back surface field (BSF) layer, wherein the BSF layer includes (In)GaAs having a thickness from 50 nm to 300 nm. 
     
     
         13 . The multijunction photovoltaic cell of  claim 12 , wherein the (In)GaAs has a thickness from 50 nm to 200 nm. 
     
     
         14 . The multijunction photovoltaic cell of  claim 1 , further comprising:
 a plurality of tunnel junctions disposed between each of the at least three subcells.   
     
     
         15 . The multijunction photovoltaic cell of  claim 14 , wherein each of the plurality of tunnel junctions includes an n-type (Al,In)GaAs layer, an n-type (Al)InGaP(As) layer, or a p-type (Al,In)GaAs layer. 
     
     
         16 . The multijunction photovoltaic cell of  claim 14 , wherein each of the plurality of tunnel junctions has a thickness less than 100 nm. 
     
     
         17 . A method of fabricating a multijunction photovoltaic cell, the method comprising:
 depositing from at least three subcells overlying a (Si,Sn)Ge substrate, wherein:
 each of the at least three subcells is lattice matched to each of the other subcells and to the (Si,Sn) Ge substrate; 
 at least one of the subcells comprises a GaInNAsSb subcell comprising a Ga 1-x In x N y As 1-y-z Sb z  base layer, wherein the Ga 1-x In x N y As x-y-z Sb z  base layer includes: 
 0.075≤x≤0.081, 0.040≤y≤0.051, and 0.010≤z≤0.018, 
 a band gap from 1.111 eV to 1.117 eV, 
 a thickness from 1 μm to 4 μm, 
 a short circuit current density Jsc greater than 9 mA/cm 2 , and 
 an open circuit voltage Voc greater than 0.4 V, 
 wherein the Jsc and the Voc are measured using a 1 sun AM1.5D spectrum at a junction temperature of 25° C. 
   
     
     
         18 . The method of  claim 17 , wherein depositing the GaInNAsSb subcell comprises depositing using molecular beam epitaxy. 
     
     
         19 . The method of  claim 17 , wherein depositing a subcell other than the GaInNAsSb subcell comprises depositing using metal organic chemical vapor deposition. 
     
     
         20 . The method of  claim 17 , further comprising after depositing the at least three subcells, annealing the at least three subcells at a temperature from 400° C. to 1000° C. for between 10 seconds to 10 hours.