Researchers at the University of Melbourne and UNSW have built a black-phosphorus and molybdenum-disulfide diode that generates electrical power through mid-infrared heat exchange with its surroundings. The authors report about 80 nanowatts per square metre in their thermoradiative test, which they describe as the first demonstration of thermoradiative power generation with van der Waals materials. The output is far below a practical power source, but the experiment shows that an atomically layered semiconductor stack can work in this less-developed counterpart to photovoltaics.
A photovoltaic diode produces current after absorbing photons from a hotter light source. A thermoradiative diode runs the energy flow in the other direction: a warm device emits infrared photons toward cooler surroundings, and the resulting electronic imbalance can drive current. The new device uses black phosphorus and molybdenum disulfide, two materials whose thin layers are bound by weak van der Waals forces, to form the junction that separates charge.
The team stacked flakes of the two semiconductors above a reflective backing and measured the voltage and current while changing the temperature difference between the device and its surroundings. When both were near room temperature, about 27 degrees Celsius, there was no temperature difference to drive the exchange.
In thermoradiative operation, with a 50-degree temperature difference and the device radiating toward cooler surroundings, the reported power density was about 80 nanowatts per square metre. A nanowatt is one billionth of a watt. In the reverse operating mode, thermophotovoltaics, the device absorbs radiation from hotter surroundings; with a 100-degree difference, it produced more than 100 microwatts per square metre. These are different thermal conditions, not competing efficiency measurements.
The authors identify two main constraints: getting emitted light out of the device and efficiently converting the underlying electronic transitions into useful current. Their model projects much larger output if those losses can be reduced, but those projections have not been demonstrated by the prototype.
The measured output remains far below that of a practical generator. What the experiment establishes is that this layered semiconductor junction can produce electrical power from infrared exchange in either direction, depending on which side is warmer.
Sources
- AIP Congress 2026 conference contribution
- Advanced Energy Materials paper
- Lead image: black phosphorus crystals in a sealed ampoule. Photo by Alshaer666 via Wikimedia Commons, licensed under CC BY-SA 3.0.
