The study of device fabrication and system integration of InGaAs thermophotovoltaic cells

InGaAs cells have the advantages of low absorption bandgap, high efficiency and great stability, which are widely used in thermophotovoltaic(TPV) devices. In this paper, the material growth, device fabrication and system integration of 0.73 eV In0.53Ga0.47As (lattice matched to InP substrate) and 0.6 eV In0.68Ga0.32As (lattice mismatched to InP substrate) thermophotovoltaic cells are studied, respectively. Based on the calculation of buffer layer thickness, the strain relaxation mechanism of the compositionally undulating step-graded InAsP buffer is analyzed. The buffer layer can release 84% of the mismatch strain at a single-layer thickness of 150 nm. The room temperature photoluminescence wavelengths of In0.53Ga0.47As and In0.68Ga0.32As are 1.69 μm and 2.05 μm, respectively. The conversion efficiencies of the 0.73 eV and 0.6 eV InGaAs TPV cells are 12.38% and 8.41%, respectively, at the AM1.5G standard spectrum. However, at 1323 K radiation temperature, the conversion efficiencies of the 0.6 eV InGaAs TPV cells outperform that of the 0.73 eV InGaAs TPV cells, which are 26.9% and 25.4% respectively after being calibrated with the blackbody radiation formula. A prototype system of thermophotovoltaic is set up by series-parallel connection of InGaAs TPV cells. It achieves output power about 5 W at a radiation temperature of 1470 K and completes a stable conversion of thermal radiation energy to electrical energy.