Tandem GaSb/InGaAsSb thermophotovoltaic cells

Computer modelling of a tandem thermophotovoltaic (TPV) system has been carried out. The monolithic GaSb/InGaAsSb tandem TPV devices have been designed and fabricated by LPE. The cell consists of: nGaSb (substrate); (n-p)In/sub x/Ga/sub 1-x/As/sub y/Sb/sub 1-y/ (E/sub g//spl ap/0.56 eV, bottom cell); p/sup ++/-n/sup ++/GaSb (tunnel junction); (n-p)-GaSb (top cell). External quantum yields of 80% at 800-1600 nm wavelength (top cell) and of about 75% at 1800-2100 nm (bottom cell) have been measured. V/sub OC/=0.61 V and FF=0.75 were achieved in a tandem cell at current density of 0.7 A/cm/sup 2/.