French lab passivated microcell shows photovoltaic effect at 273 K

Inside a laboratory setup in France, a small thermophotovoltaic cell faced an 800 C thermal emitter. The device produced electricity from the emitter’s infrared radiation—and a passivated version still showed a photovoltaic effect at 273 K, around 0 C. That is the new result: a very-low-bandgap cell working at temperatures warmer than those usually used for infrared photodetectors.

Thermophotovoltaics, or TPV, convert heat radiation directly into electricity rather than first turning the heat into motion. Very-low-bandgap cells can respond to lower-energy infrared radiation, which is useful for lower-temperature heat sources. Their weakness is dark current: unwanted electrical flow that remains even without incoming radiation, reducing voltage and power output.

The researchers addressed that leakage with a 200 nm aluminum arsenide antimonide barrier layer in an indium arsenide/indium arsenide antimonide absorber. The barrier creates an energy offset that restricts carrier flow through the device. Combined with a surface-passivation treatment, it helped the barrier structure perform more than tenfold better than a conventional PIN structure at temperatures above 150 K.

The measurements show both the promise and the distance still to travel. At 123 K, the barrier cells recorded open-circuit voltages of around 23 mV and fill factors of about 0.2; one measurement produced 0.15 V. The work was performed on micro and 1 × 1 cm² macro cells, and the researchers say the characterization setup and absorber bandgap still need improvement.

So what changes in practice? If the design survives further testing, it could reduce the cooling burden for TPV systems aimed at thermal energy storage or industrial process heat, where infrared energy is otherwise lost. For now, it is a laboratory result rather than a deployed generator, and the reported figures come from the research team’s tests under a controlled infrared source.