Photovoltaic Cells Based on GaSb and Ge for Solar and Thermophotovoltaic Applications

Abstract

In the present work, high efficient photovoltaic (PV) cells based on gallium antimonide have been developed and fabricated with the use of the liquid phase epitaxy (LPE) and diffusion from the gas phase techniques. They are intended for conversion of the infrared (IR) part of the solar spectrum into electricity by tandems of mechanically stacked cells and for conversion of the thermal radiation of emitters heated by the sunlight. On the ground of investigation of the LPE temperature regimes and the tellurium doping effect, GaSb PV cells have been fabricated with the efficiency of 6% at the concentration of 300 suns behind the single-junction GaAs top cell and of 5.6% at the same sunlight concentration of the cells behind the dual-junction GaInP∕GaAs structure, the substrate thickness being 100μm (the efficiency of PV cells was calculated for AM1.5D Low AOD spectrum, 1000W∕m2). The rated efficiency of conversion of solar powered tungsten emitter radiation by PV cells based on gallium antimonide in a thermophotovoltaic (TPV) module appeared to be about 19%. Photovoltaic cells based on germanium with a wide-gap GaAs window grown by LPE or metalorganic chemical vapor deposition and with a p-n junction formed by means of the zinc diffusion from the gas phase have been fabricated. Ge based PV cells without a wide-gap GaAs window had the efficiency of up to 8.6% at a concentration of 150 suns. The efficiency of Ge based cells with a wide-gap GaAs window was 10.9% at the concentration of 150 suns. 4.3% efficiency Ge cells behind a single-junction GaAs top cell at the concentration of 400 suns have been also obtained. The maximum rated conversion efficiency of Ge PV cells appeared to be about 12% in the case of conversion of the tungsten emitter thermal radiation. These efficiency values for Ge based cells are among the highest.