Observation of anomalous excitonic emission in V-doped WS2 QDs synthesized by hydrothermal method and subsequent mechanical exfoliation

Abstract

This study focuses on synthesizing vanadium (V) doped 2H phase WS₂ via a facile hydrothermal method and subsequent liquid phase mechanical exfoliation of the material into QD-like nanostructures. An increment in dopant percentage from 1 % to 7 % red shifted the band gap of WS₂ from 4.15 eV to 3.78 eV. The nanostructures show electronic transition due to B, A, and defect-bound excitons and demonstrate modulation of excitonic behavior with V doping. Low V doping provides the WS₂ material with a reduced B/A excitonic peak intensity ratio because of the nonradiative pathways favoring the relaxation of high energy B excitons to A excitons. High V doping results in anomalous emission behavior marked by an increased B/A ratio, attributed to positive trion formation as a result of excess free hole concentration due to the p-type vanadium. The study suggests that V-doped WS₂ nanostructures hold potential for technological applications, particularly in spintronics and photonics, emphasizing the importance of engineering exciton dynamics in two-dimensional materials using p-type substitutional dopants.