Several types of conversion are investigated, most often involving a p-n diode exchanging thermal radiation with its surroundings:
– mainly thermophotovoltaic conversion, where a photovoltaic cell (cold body) converts thermal radiation from a hot body,
– an extension, called thermophotonic conversion, where the hot body is also a radiation-emitting p-n diode (Light Emitting Diode, LED),
– thermoradiative conversion, where the p-n diode generating electrical power is the hot body exchanging radiation with a colder environment,
– rectenna conversion, which converts light into direct current without using the photoelectric effect.