The performance analysis of near-field thermophotovoltaics considering temperature dependence of indium tin oxide emitter

Near-field thermophotovoltaics (NFTPV) is of great interest because it can achieve both high power density and high efficiency at medium to high temperature. One key to efficient photovoltaic conversion is an emitter that can selectively emit spectrum. Indium tin oxide (ITO) is considered as the emitter for NFTPV because its plasma frequency is tunable by simple technical means. However, as a typical degenerate semiconductor, the temperature dependence of its dielectric constant is often neglected in studying the performance of NFTPV. Therefore, we propose a NFTPV model considering the temperature-dependent property of ITO. By changing the applied voltage V, the vacuum gap d, and the emitter temperature T1, the performance of NFTPV with and without temperature dependence is compared and shows a significant difference. We find that the heat flux is always underestimated as well as the optimal efficiency is overestimated when the temperature dependence is not considered. At d = 10 nm and T1 = 1000 K, the optimal efficiency is even overestimated by about 270%. Without considering the temperature dependence, the output power is overestimated at d