Near-field thermophotovoltaics for efficient heat to electricity conversion at high power density

Thermophotovoltaic approaches exploiting near-field evanescent modes offer the potential for high power density and efficiency, but progress has been limited by the lack of thermally robust planar emitters and PV cells optimized for near-field radiation. Here, we demonstrate record power densities of ~5 kW/m^2 at an efficiency of 6.8%, where efficiency is defined as the ratio of electrical power output to the radiative heat transfer from emitter to PV cell. This is achieved using novel doped-silicon emitter microdevices operating up to 1270 K positioned within <100 nm of custom InGaAs thin-film PV cells. We characterize performance across emitter temperatures ~800–1270 K and gap sizes 70 nm–7 µm, and provide modeling and experimental insights into efficient near-field heat-to-electricity conversion.