High performance polarization-sensitive self-powered imaging photodetectors based on a p-Te/n-MoSe2van der Waals heterojunction with strong interlayer transition

In-plane anisotropic two-dimensional (2D) materials offer great opportunities for developing novel polarization sensitive photodetectors without being in conjunction with filters and polarizers. However, owing to low linear dichroism ratio and insufficient optical absorption of the few layer 2D materials, the comprehensive performance of the present polarization sensitive photodetectors based on 2D materials is still lower than the practical application requirements. In this work, after systematic investigation of the structural, vibrational, and optical anisotropies of layer-structured Te nanosheets, a novel polarization-sensitive self-powered imaging photodetector with high comprehensive performance based on a p-Te/n-MoSe₂ van der Waals heterojunction (vdWH) with strong interlayer transition is proposed. Owing to the high rectification ratio (10⁴) of the diode, the device shows excellent photovoltaic characteristics. As examples, the photodetectors exhibited an ultrahigh on/off ratio of 10⁵ at a relatively weak light intensity (4.73 mw cm^-2), and the highest responsivity of the device could reach 2106 mA W^-1 without any power supply. In particular, benefitting from the excellent dichroism properties of Te nanosheets synthesized in this work, the anisotropic ratio of the photocurrent (I_max/I_min) could reach as high as 16.39 (405 nm, 24.2 mw cm^-2). This value obtained under zero bias voltage is much greater than that of present 2D material photodetectors even at a bias voltage. In addition, the highest detectivity is 2.91 × 10¹³ Jones at a low bias voltage of -0.08 V. This work provides a novel building block for high resolution polarization-sensitive photodetection of weak signals in complex environments.