Low bandgap InGaAs thermophotovoltaic cells

Thermophotovoltaic (TPV) systems convert low energy photons from low temperature heat sources into electrical power by means of photovoltaic cells. This paper describes low-bandgap indium gallium arsenide (In_xGa_1-xAs) cells used in such systems whose composition can be “tuned” to particular wavelengths of interest. The intent of this paper is to give an overview of these cells and enough useful data so that TPV system designers can predict the performance of these cells in particular applications. Data are presented for 1.65 μm (0.74 eV bandgap, In_0.53Ga_0.47 As) as well as 2.25 μm (0.55 eV, In_0.72Ga_0.28 As) cutoff wavelength cells. Cell short-circuit photocurrent densities up to 5 A/cm² and open-circuit voltages over 480 mV (0.74 eV cells) and 310 mV (0.55 eV) are obtainable. Measured responsivity, dark current, and series resistance are presented and are used to numerically determine maximum output power for 0.55 eV and 0.74 eV InGaAs cells at blackbody temperatures of 1000 to 1500°C