GaSb-related materials for TPV cells

A survey of materials options and technologies for GaSb-related thermophotovoltaic (TPV) cells is presented, followed by an overview of device design principles and issues. This device technology has been developed for thermal-to-electric generator systems with thermal emitter infrared sources operated in the 1000–1200 °C range. Significant results for the growth, material characterization and device performance of TPV cells based on InGaAsSb, InGaSb, AlGaAsSb and InAsSbP fabricated by LPE, MOCVD, MBE and diffusion methods are reviewed. For single-junction TPV cells, epitaxial heterostructures with a ~0.53 eV bandgap InGaAsSb base layer and wide-bandgap AlGaAsSb or GaSb window/cladding layers (all closely lattice matched to a GaSb substrate) represent the state of the art. As an alternative, a low-cost Zn-diffusion technology for fabrication of InGaAsSb p–n homojunction structures has been developed for producing the high efficiency TPV cells. External quantum yields as high as 90% at wavelengths (around 2000 nm wavelength), and response edges to about 2400 nm wavelength have been obtained with these TPV cells. Multijunction tandem TPV devices based on GaSb top cells and InGaAsSb bottom cells provide even higher performance. TPV cells based on InAsSbP, also reviewed here, have spectral responses in wavelengths in the 2.5–3.5 μm range, and thus provide a means for utilizing radiation from thermal emitters with lower temperatures.