Monolithically series-interconnected GaInAsSb/AlGaAsSb/GaSb thermophotovoltaic devices with an internal backsurface reflector formed by wafer bonding

GaInAsSb/AlGaAsSb/GaSb thermophotovoltaic (TPV) cells were monolithically interconnected in series to build open-circuit voltage Voc. GaInAsSb epitaxial layers were transferred to GaAs by wafer bonding with SiOx/Ti/Au, which provides electrical isolation of individual cells and forms an internal backsurface reflector. This configuration is compatible with monolithic series interconnection of TPV cells; can mitigate the requirements of filters used for front-surface spectral control; and has the potential to improve TPV device performance. Wafer-bonded GaInAsSb TPV cells exhibit nearly linear voltage building. At a short-circuit current density of 0.4 A/cm2, Voc of a single TPV cell is 0.2 V, compared to 0.37 and 1.8 V for 2- and 10-junction series-interconnected TPV cells, respectively.