Photo-Thermoelectric Thin-Film Generator and Sensor With Ultrahigh Output Voltage and Large Responsivity

The thin-film thermoelectric device has gained much attention as promising candidate for micro-energy conversion and sensing. However, its relatively low responsivity is one of the main obstacles in light detection field due to the limited response voltage, which is determined by the properties of thermoelectric films as well as the device configuration. In this letter, we develop a compatible micromachining technology including photolithographic and lift-off processes to fabricate thin-film thermoelectric device with high integration of thermocouple on flexible substrates. Meanwhile, the properties of thermoelectric films have been optimized during the fabrication process. In addition, by integrating the photothermal layer and Fresnel lens with increased temperature difference, the assembled device can exhibit an ultrahigh output voltage, which achieves 1.25 V under 1.5 AM 1-sun condition. The light sensing performance of the device is also investigated, and the responsivity reaches up to 24.9 V/W. This work presents a significant progress toward a photo-thermoelectric thin-film sensor in light detecting field.