The mechanism that activates a bi-junction power generator under the effects of heat is the Seebeck effect, that is, the production of voltage difference DV(t) is directly proportional to the temperature difference DT(t) between the ''hot'' and ''cold'' junctions of the device. This phenomenon is well established and is known as thermoelectric power generation. Here, it is shown that, instead, the causal and linear relationship between DV(t) and DT(t) is lost when continuous broadband infrared (CB-IR) radiation illuminates a bi-junction power generator in an insulated compartment. The observed phenomenon is IR power generation. Heat transfer calculations fail in explaining the experimental trends. The interaction between CB-IR radiation and the charge carriers in the bi-junction power generator might play a role in the DV(t) production, depending upon the geometry of the experimental setup. The longitudinal propagation of collective oscillations, for example, polaritons, in the plates protecting the ''hot'' and ''cold'' junctions of the bi-junction power generator could explain the DV(t) production and the characteristic time constants. The findings should be considered in the design, fabrication, and improvement of thermopiles, power meters, and IR energy-harvesting devices.

The Seebeck coefficient S is a temperature-and material-dependent property, which linearly and causally relates the temperature difference T ∆ between the "hot" and "cold"

The interaction between infrared radiation and a power generator device in time is studied as a route to harvest infrared, and possibly other electromagnetic radiations. Broadening the spectrum of the usable electromagnetic spectrum would greatly contribute to the renewable and sustainable energy sources available to humankind. In particular, low frequency and low power radiation is important for applications on ships, satellites, cars, personal backpacks, and, more generally, where non-dangerous energy is needed at all hours of the day, independent of weather conditions. In this work, we identify an electric and an entropic contribution to the energy transfer from low power infrared radiation to the power generator device, representing electrical and thermal contributions to the power generation. The electric contribution prevails, and is important because it offers multiple ways to increase the voltage produced. For example, placing black-colored gaffer tape on the illuminated face doubles the voltage produced, while the temperature difference, thus the entropic contribution, is not sensitive to the presence of the tape. We recognize the electric contribution through the fast changes it imparts to the voltage output of the power generator device, which mirror the instabilities in time of the infrared radiation. The device thus acts as sensor of the infrared radiation's behavior in time. On the other hand, we distinguish the entropic contribution through the slow changes it causes to the voltage output of the power generator device, which reflect the relative delay with which the two faces of the device respond to thermal perturbations.

Infrared radiation is used to radiatively transfer heat to a nanometric power generator (NPG) device with a thermoelectric Nb-doped TiO2 film deposited by atomic layer deposition (ALD) as the active element, onto a borosilicate glass substrate. The linear rise of the produced voltage with respect to the temperature difference between the “hot” and “cold” junctions, typical of the Seebeck effect, is missing. The discovery of the violation of the Seebeck effect in NPG devices combined with the ability of ALD to tune thermoelectric thin film properties could be exploited to increase the efficiency of these devices for energy harvesting purposes.