Thermophotovoltaic Energy Conversion Systems

Thermophotovoltaic energy conversion systems directly transform thermal radiation into electrical power by harnessing the photovoltaic effect. At their core, these systems consist of a hot emitter that radiates photons and a photovoltaic cell optimised for a specific bandgap. Thermal sources can include industrial waste heat, concentrated solar energy or combustion by-products. Engineered emitters selectively enhance emission in the near-infrared range, matching the semiconductor’s absorption band and reflecting sub-bandgap photons back to the heat source for recycling. Architectures span far-field devices with millimetre-scale gaps to near-field configurations exploiting evanescent modes across nanometre-scale separations for boosted radiative transfer. Advances in materials, nanostructuring and thermal stability have addressed challenges in spectral control, power density and durability, bringing thermophotovoltaics closer to practical applications in waste-heat recovery, solar-driven power and grid-scale thermal storage.

Research from Nature Portfolio

Recent studies have reported tandem III–V thermophotovoltaic cells achieving efficiencies exceeding 40 per cent under emitter temperatures above 2 000 °C. These high-bandgap devices employ band-edge spectral filtering and highly reflective back surface reflectors to reject unusable sub-bandgap radiation, thereby boosting electrical output and minimising thermalisation losses. Foundational work introduced refractory metamaterials engineered around an epsilon-near-zero transition to control thermal emission at temperatures up to 1 000 °C. By relying on a topological transition rather than lithographically defined resonances, these materials deliver near-omnidirectional, spectrally selective emission without angle dependence. Complementary research on ultra-thin thermal wells has shown that reducing emitter and cell thickness can confine photons in trapped waveguide modes, simultaneously enhancing emission selectivity and reducing carrier recombination in the photovoltaic absorber, leading to predicted efficiencies above 30 per cent.

Thermophotovoltaic Energy Conversion Systems publication trend

The graph below shows the total number of articles in thermophotovoltaic energy conversion systems across all publications each year (not limited to Nature Index journals).

Technical terms

Thermophotovoltaic (TPV): A device that converts thermal radiation into electricity through the photovoltaic effect by matching emitter spectra to a photovoltaic cell’s bandgap.

Selective emitter: A material or structure engineered to emit thermal radiation predominantly within a target wavelength range tuned to a photovoltaic cell’s optimal absorption band.

Bandgap: The minimum energy difference between the valence and conduction bands in a semiconductor; photons below this energy cannot generate electrical current.

Near-field regime: A configuration in which the emitter and photovoltaic cell are separated by nanometre-scale distances, enabling evanescent wave coupling and enhanced radiative transfer beyond far-field limits.

Epsilon-near-zero (ENZ) metamaterial: An engineered medium whose permittivity approaches zero at a designed frequency, allowing independent control of spectral and directional thermal emission without reliance on surface resonances.

References

1. Enhanced power density in zero-vacuum-gap thermophotovoltaic devices. Energy & Environmental Science (2025).
2. A review on current development of thermophotovoltaic technology in heat recovery. International Journal of Extreme Manufacturing (2024).
3. Controlling thermal emission with refractory epsilon-near-zero metamaterials via topological transitions. Nature Communications (2016).
4. Thermophotovoltaic efficiency of 40%. Nature (2022).
5. Thin-film ‘Thermal Well’ Emitters and Absorbers for High-Efficiency Thermophotovoltaics. Scientific Reports (2015).