Bending strain-modulated flexible photodetection of tellurene in the long wavelength infrared region

Single-element van der Waals material has triggered a booming exploration since its simple theoretical modeling and highly integration ability. Elemental tellurium (Te) has a narrow band gap, high environmental stability and superior photoelectronic properties, making it one of the strong candidate materials for advanced broadband photodetectors. Moreover, its asymmetrical chain structure and inherent anisotropic piezoelectricity lays the foundations for artificial modification by strain-engineering. In this study, the Te-based prototype photodetectors were demonstrated with a stable, strong photoresponse at lambda = 10.8 mu m at room temperature. The photo-responsivity and detectivity were 9.34 mA/W and 8.63 x 107 Jones and can be enhanced by mechanical bending strain. The convex strain of 0.33 % significantly suppresses the dark current of Te photodetector since the stretching of Te-Te bond increases the inherent electrical resistance, which in turn enhances its photoresponsivity to 1080 %. Besides, we observed the bending direction is closely related to the modulation mechanism. The concave bending greatly improved the effective light absorption by rolling up the flexible device in the direction of light radiation, which dominants the enhanced photocurrent and photoresponsivity reaches 60.03 mA/W. This work demonstrates a feasible approach for enhancing Te-based infrared photodetection through an appropriate mechanical stimulus, and should has immense potential for the flexible applications of piezoelectronics and optoelectronics.