The group led by Prof. Peng Jiang and Prof. Xinhe Bao from Dalian Institute of Chemical Physics (DICP), Chinese Academy of Sciences, made an important progress on the novel photothermoelectric detector based on SrTiO₃. The paper entitled “Phonon-enhanced photothermoelectric effect in SrTiO₃ ultra-broadband photodetector” was published in Nature Communications (https://www.nature.com/articles/s41467-018-07860-0).

Photothermoelectric detector is based on two basic energy conversion processes: photothermal and thermoelectric conversions. When one end of thermoelectric materials is illuminated by the light, the temperature gradient across the thermoelectric materials will be built up. Due to the Seebeck effect, the temperature gradient will drive the charge carriers to diffuse from the high-temperature end to the low-temperature end, leading to the generation of electric potential difference. Photothermoelectric detector exhibits several outstanding characteristics, including self-powered, uncooled and broadband spectral response. Therefore, the photothermoelectric detectors are widely used in military and civil fields, such as optical power meter, infrared thermal imaging and temperature supervision.

The responsivity of photo-thermoelectric detector is in proportion to the product of Seebeck coefficient (S) and the temperature difference (ΔT) between the two ends of the thermoelectric material. In traditional photothermoelectric detectors, conventional thermoelectric materials (i.e., Bi₂Te₃ and Sb₂Te₃) with Seebeck coefficient less than 200 μV/K are commonly employed. To improve the responsivity of this kind of photothermoelectric detector, the complicated micro-fabrication technology is utilized to produce array module, resulting in high production cost. Herein, instead of using traditional thermoelectric materials, strontium titanium oxide (SrTiO₃) with room-temperature Seebeck coefficient of up to 1000 μV/K is employed. Furthermore, for SrTiO₃, there exists strong phonon absorption in the long-wavelength infrared atmospheric window (8-14 μm), indicating the high photothermal conversion efficiency. Based on these two properties, the responsivity of the single-element SrTiO₃ photothermoelectric detector can reach 1.2 V/W at around 10 μm wavelength. The spectral response of the SrTiO₃ photothermoelectric detector covers deep ultraviolet to far infrared and the endurable power density can reach 10³ W/cm².

This work opens up a new avenue for the development of the novel high-performance photothermoelectric detector. Moreover, considering the environmental friendliness, low material cost and high-temperature stability of SrTiO₃ as well as excellent performance and simple manufacturing process, SrTiO₃ photothermoelectric detector will have a bright future for practical applications.

 This work is financially supported by National Key Research and Development Program of China and Dalian Institute of Chemical Physics. (By Xiaowei Lu)