Viable power supply methods capable of replacing the need for batteries are a key design factor for realization of emerging technologies and platforms based on self-sustainable standalone electronics. Hence, alternate possibilities should arise by developing semiconductor devices with an inherent energy source, i.e., a device that simultaneously exhibits energy-converting as well as amplifying-modulating properties. In the present Letter, we report a proof-of-concept photo-thermoelectric modulator. Thereby, an optical signal is reproduced by the thermoelectric voltage generated by modulating, with a light beam, the free carrier concentration of a photoconductive PbS film that is under a temperature gradient. Experimental results unveil that photo-generated electrons affect more electrical conductivity than thermal conductivity, giving rise to a drastic change in thermoelectric power. Consequently, it induces significant changes in the thermoelectric figure of merit of the device, and thus, signal modulation is mainly awarded to photo-generated electrons rather than thermal effects. Therefore, the device developed here establishes the basis for the development of an elementary batteryless photo-thermoelectric transistor and opens alternative avenues for self-powered devices that are driven by temperature gradients via a photo-thermoelectric effect.

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