Pressure‐Dependent Strong Photoluminescence of Excitons Bound to Defects in WS₂ Quantum Dots

Abstract

There are various efforts to tailor the excitonic properties in monolayer transition metal dichalcogenides (TMDs) for exploring their potential applications in optoelectronic devices. However, the low quantum yields (QYs), despite their direct bandgap nature, have limited the application in much fields. Encouragingly, excitons combined with defects endow WS2 quantum dots (QDs) with certain desirable properties through strain engineering. A strong exciton photoluminescence (PL) of WS2 QDs even up to ≈20 GPa by PL measurements is reported. Their PL reveals that a distinct defect‐induced peak D is located below the neutral exciton peak A. This peak D originates from defect‐bound excitons and intensifies with increasing pressure as more electrons transfer from WS2 QDs to O2. In addition, a transition from direct to indirect bandgap above 4.5 GPa is revealed by both experimental measurements and theoretical calculations. The evolution of electronic structure is related to lattice structural distortion. The results provide a new direction for modulating the optical properties of TMDs QDs through utilizing defects–excitons interactions. The pressure‐tuned emission of excitons combined with strong PL from defects sites of WS2 QDs may have promising applications in optoelectronic devices.

Fine-Tuning of the Excitonic Response in Monolayer WS2 Domes via Coupled Pressure and Strain Variation

“…41 The final remark is on the pressure trend of the relative intensity of A 1L−dome with respect to that of T 1L−dome , shown in Figure 3f. Differently from high-pressure PL measurements on exfoliated TMD monolayers, 42 in the present case, we observe a continuous spectral weight transfer from T 1L−dome to A 1L−dome on increasing pressure. This anomalous behavior can be traced back to the morphological evolution of the 1L-dome.…”

Research on the oxygen and humidity related-electrical behavior of monolayer MoS2 under vacuum to normal pressures

“…For molybdenum disulfide (MoS 2 ), a key member of the TMDCs family, both theoretical and experimental studies have been conducted to examine its unique bandgap transition phenomenon and Raman spectrum variation as the applied pressure varies from 0 GPa to several tens of GPa [9,10]. In addition, some similar methods have been proposed to report the pressure-dependent optical, electrical and magnetic properties of other TMDCs such as WS 2 , MoSe 2 , and WS 2 [11][12][13][14][15][16], most of these studies are focused on the pressure-dependent behavior of TMDCs under high pressures, rather than a complete range of pressures, especially from vacuum to normal pressures.…”