Thermophotovoltaic efficiency of 40%

Thermophotovoltaics (TPVs) convert predominantly infrared wavelength light to electricity via the photovoltaic effect, and can enable approaches to energy storage(1,2) and conversion(3-9) that use higher temperature heat sources than the turbines that are ubiquitous in electricity production today. Since the first demonstration of 29% efficient TPVs (Fig. 1a) using an integrated back surface reflector and a tungsten emitter at 2,000 degrees C (ref.(10)), TPV fabrication and performance have improved(11,12). However, despite predictions that TPV efficiencies can exceed 50% (refs.(11,13,14)), the demonstrated efficiencies are still only as high as 32%, albeit at much lower temperatures below 1,300 degrees C (refs.(13-15)). Here we report the fabrication and measurement of TPV cells with efficiencies of more than 40% and experimentally demonstrate the efficiency of high-bandgap tandem TPV cells. The TPV cells are two-junction devices comprising III-V materials with bandgaps between 1.0 and 1.4 eV that are optimized for emitter temperatures of 1,900-2,400 degrees C. The cells exploit the concept of band-edge spectral filtering to obtain high efficiency, using highly reflective back surface reflectors to reject unusable sub-bandgap radiation back to the emitter. A 1.4/1.2 eV device reached a maximum efficiency of (41.1 +/- 1)% operating at a power density of 2.39 W cm(-2) and an emitter temperature of 2,400 degrees C. A 1.2/1.0 eV device reached a maximum efficiency of (39.3 +/- 1)% operating at a power density of 1.8 W cm(-2) and an emitter temperature of 2,127 degrees C. These cells can be integrated into a TPV system for thermal energy grid storage to enable dispatchable renewable energy. This creates a pathway for thermal energy grid storage to reach sufficiently high efficiency and sufficiently low cost to enable decarbonization of the electricity grid.

Automated summary

Thermophotovoltaics (TPVs) convert infrared light into electricity, enabling energy storage and conversion using high temperature heat sources. This study reports the fabrication and measurement of high-efficiency TPV cells, demonstrating the efficiency of high-bandgap tandem TPV cells.