- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Screening Effect of Ultrathin Gold Films on Excitons in Monolayer WS2
摘要： Screening plays an important role in determining the energy levels and binding energies of excitons in two-dimensional (2D) semiconductors. However, the photoelectric properties of 2D materials deposited upon metal films are often assumed to remain unaffected by the screening effect. Herein, we derive the reflectance contrast spectra of monolayer WS2 on different thicknesses of ultrathin gold films by using the transfer matrix method, and investigate the screening effect of ultrathin gold films on excitons in monolayer WS2. We show that the exciton binding energy of the ground state gradually decreases as the gold film thickness increases due to the enhanced screening effect. Nevertheless, it may be due to the impact of free-electron scattering on the permittivities of gold films: exciton resonance energies of the ground state and the first excited state gradually increase as the gold film thickness increases, which are different from previously reported variation trend of exciton energy levels with the thickness of screening media of 2D materials. As a consequence, the electronic bandgap of the exciton only presents a small variation range of less than 4 meV with thickening of the gold film from 0.0 to 40 nm. These findings shed light on understanding to what extent the screening effect of gold films affects the excitons in 2D materials.
关键词： Ultrathin gold film,Transfer matrix method,Excitonic properties,Monolayer WS2,Dielectric screening effect
更新于2025-09-23 15:22:29
-
Hole Transfer Promoted by a Viscosity Additive in an All-Polymer Photovoltaic Blend
摘要： Viscosity modi?ers are widely applied to improve the mechanical compliance of organic optoelectronic devices. However, the e?ect of the viscosity additives on the charge dynamics remains poorly understood. Here, we report the observation of markedly di?erent e?ects of a high-viscosity polymeric additive on the electron- and hole-transfer dynamics in all-polymer organic photovoltaic blends. By using ultrafast transient absorption spectroscopy, we determine that hole transfer from charge-transfer excitations in the acceptor is markedly promoted while the electron transfer from local excitations in the donor remains nearly unchanged upon introduction of viscosity additives into the blends. We argue that the modi?cation of dielectric screening is the mechanism underlying the e?ect of the additive on the charge dynamics. This ?nding suggests a new strategy for designing high-performance ?exible organic photovoltaic devices by manipulating the dielectric environment.
关键词： electron transfer,hole transfer,viscosity additives,dielectric screening,all-polymer photovoltaic blends
更新于2025-09-19 17:13:59