Nature of Photoconductivity in Self-Powered Single-Atomic-Layered Nb-Doped WSe₂ Phototransistors

Abstract

Although single-atomic-layered alloys are regarded as promising components for improving the performance of broadband photodetectors, the origin of their enhanced photoresponsivity due to the introduction of dopants in the crystal lattice has not yet been investigated in depth. Herein, we comprehensively analyze the nature of the photoconductivity of a photodetector based on a niobium (Nb)-doped WSe2 monolayer. The Nb-doped WSe2 photodetector exhibited superior responsivity and specific detectivity compared with those of the undoped WSe2 photodetectors. Experimental and density functional theory analyses revealed that the introduction of Nb not only modified the Fermi level of WSe2 but also generated multiple electron-trapping sites, thereby increasing both the photovoltaic and photogating effects to improve the photocurrent of the device. We believe that this research presents a sophisticated approach to achieve photodetectors based on single-atomic-layered alloys, which are both highly sensitive and energy-efficient.

Two-dimensional materials for future information technology: status and prospects

“…Substitutional dopant atoms have been further expanded to transition metal elements with different electron occupancy. The substitution of metal atoms with Mn or Re results in n-type doping of TMDs [187,188], while p-type dopant Nb or V can also be incorporated into W-based TMDs [189][190][191]. It is noted that the foreign atoms prefer to be adsorbed on the surface rather than be substituted into the lattice if their radius or coordination numbers mismatch with the 2D substrate.…”

Polarization-Sensitive Self-Powered Schottky Photodetector with High Photovoltaic Performance Induced by Geometry-Asymmetric Contacts

“…Constructing self-powered Schottky photodiodes through a facile asymmetric contact is a simple but effective way, which is expected to achieve remarkable photovoltaic performance and polarization sensitivity. − In general, the Schottky photodiodes with a larger Schottky barrier height difference at the metal/semiconductor interface can be classified into two categories: asymmetric electrodes and geometry-asymmetric contacts. For the former, Park et al synthesized Nb-doped WSe 2 and fabricated a Schottky junction photodetector by using Pd and Ti asymmetric electrodes, in which maximum I light / I dark exceeding 10 3 and an ultralow leakage current of approximately 10 –12 A at V ds = 0 V were obtained, but the polarization sensitivity is not included owing to the isotropic WSe 2 . Recently, semimetal PdSe 2 with a highly asymmetric crystal structure was currently used to construct a Schottky heterojunction with other 2D or three-dimensional (3D) materials, which achieved excellent photoelectrical performance and polarization sensitivity in an ultrabroadband detection range from ultraviolet to mid-infrared, highlighting its great potential for polarized photodetection. ,, Besides, Mao et al fabricated wafer-scale Pd/semimetal 1T′-MoTe 2 /Au self-powered photodetectors, which has a promising prospect in scalable fabrication.…”

Effect of niobium doping on excitonic dynamics in MoSe2

“…The charge transport properties of niobium-doped TMDs in field-effect transistors have also been explored [43,44,48,[60][61][62][63]. Furthermore, niobium doping has enhanced the performance of TMD-based devices in photodetection [64], photovoltaic [40,65,66], thermoelectric [67], and electrocatalytic hydrogen evolution devices based on TMDs [45].…”