Structural Design and Pyroelectric Property of SnS/CdS Heterojunctions Contrived for Low‐Temperature Visible Photodetectors

The traditional photodetectors based on photoelectric effect exhibit inferior response or even out of operation with the decrease of temperature. However, cryogenic visible light detection is increasingly demanded in deep space and polar exploration. Herein, a self‐powered visible photodetector coupling pyroelectricity and photoelectricity to optimize the cryogenic detecting performance is designed in which hydrothermally grown CdS nanorod array is covered by SnS nanoflakes. The choice of SnS allows the detector with strong visible light absorption and great photoelectric conversion efficiency, while the CdS nanorod structure with pyroelectricity can effectively modulate the behavior of photogenerated carriers at low temperatures. It is found that the response characteristics of the photodetector are dominated by the combination of pyroelectric and photoelectric effects, which becomes more significant with the reduced temperature. Specifically, at 130 K temperature, the photoresponse current under 650 nm light is improved by 7.5 times as that at room temperature, while the ratio of pyroelectric current to photocurrent can be increased to 400%. Meanwhile, the responsivity and detectivity are as high as 10.4 mA W−1 and 3.56 × 1011 Jones, respectively. This work provides a promising approach to develop high‐performance self‐powered visible photodetectors with low‐temperature operating capability. Low‐temperature visible photodetectors are necessary for military applications and space and polar explorations. This paper proposes a method to improve the low‐temperature visible detecting performance by using a pyroelectric effect. An SnS/CdS heterojunction is successfully fabricated, with an enhanced detecting current and fast response speed at 130 K in the self‐powered mode.