PETE: A Hybrid Photonic and Electronic Thermoelectric Device for Direct Heat-to-Electricity Conversion
Photonic heat engines can achieve high conversion efficiencies, but their far-field power density is constrained by the blackbody limit. Near-field devices overcome this limitation through photon tunneling across a nanoscale vacuum gap; however, the mechanical spacers required to maintain this gap introduce parasitic heat conduction. We propose PETE (Photonic and Electronic Thermoelectric), a hybrid solid-state architecture in which thermoelectric generator (TEG) legs replace passive spacers. The legs simultaneously maintain the near-field gap and convert conducted heat into electricity. We evaluate PETE using an indium tin oxide emitter, an indium arsenide photovoltaic cell, and TaFeSb- and ZrNiSn-based Half-Heusler thermoelectric materials. At a hot-side temperature of 977K, the device achieves a power density of 18.6 W$\cdot$cm$^{-2}$ at 19.76% efficiency. This power density is approximately twice that of either the standalone near-field thermophotovoltaic device or the standalone TEG, while the efficiency is 44% higher than that of the standalone TEG. The performance can be tuned through thermoelectric geometry and material selection, and its adaptability is demonstrated for a broad range of thermoelectric materials and operating temperatures. PETE provides a general strategy for recovering spacer-mediated heat leakage in near-field photonic heat engines.