GaSb on GaAs interfacial misfit solar cells

The GaAs/GaSb interface misfit design can achieve comparable efficiency to conventional inverted metamorphic multijunction cells at up to 30% cost reduction. In this preliminary work, GaSb single junctions were grown via molecular beam epitaxy on both GaSb and GaAs substrates to compare and fine tune the interfacial misfit growth process. Current vs voltage results show that the best homo-epitaxial cell achieved 5.2% under 35-sun concentration. TEM did not reveal any threading dislocations in the hetero-epitaxial cells, however, device results indicated higher non-radiative recombination than expected, likely due to unpassivated surface states. Improvements to cell processing will be explored and more characterization is planned to determine the cause of degraded hetero-epitaxial cell performance.