FTIR and FT-PL Spectroscopic Analysis of TPV Materials and Devices

Fourier transform (FT) spectroscopic techniques are useful in determining properties of thermophotovoltaic (TPV) materials and devices. The III-V TPV absorber materials have energy bandgaps that can be optimized for conversion of the near-infrared radiation emitted by thermal sources in the 1000-2000 deg. C temperature range. The bandgaps of these materials can be measured at room temperatureusing FT-photoluminescence spectroscopy, which can be done with a modified FT-Raman spectrophotometer operating in the near-infrared spectral region. The intensities and bandwidths of the FT-PL spectra also provide information on the extent of non-radiative recombination and the compositional uniformity of the materials. To achieve adequate operating efficiencies, TPV converters must returnsub-bandgap radiation to the thermal source. The percent reflectance of the device in the mid-infrared spectral region is therefore an important operating parameter that can be accurately measured using FT-infrared (FTIR) spectroscopy with total reflectance optical accessories. In this paper, we discuss applications of these techniques to TPV materials and devices, and variations on theseapproaches.