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Photogenerated-Carrier Separation and Transfer in Two-Dimensional Janus Transition Metal Dichalcogenides and Graphene van der Waals Sandwich Heterojunction Photovoltaic Cells
摘要： Two-dimensional (2D) Janus transition metal dichalcogenides (JTMDs) show direct band gaps and strong visible-light absorption with promising applications in photovoltaic (PV) cells. Here, we investigate the electronic structures and dynamics of photogenerated carriers in 2D JTMDs and graphene van der Waals sandwich heterojunction (G/JTMDs/G) photovoltaic cells by using first-principles calculations. We find that the intrinsic built-in electric field in JTMDs results in an asymmetry potential, which can be used to effectively enhance the separation and transfer of photogenerated carriers from JTMDs to different graphene layers with a preferred direction within hundreds of femtoseconds in the G/JTMDs/G heterostructures. Furthermore, the photogenerated electrons (holes) can transfer from monolayer MoSSe (MoSeTe) to the graphene sheets by the Se side with lower (higher) potential, while the transfer of the photogenerated holes (electrons) is prohibited due to the large separation between donor and acceptor states.
关键词： First-principles calculations,van der Waals heterostructures,Janus transition metal dichalcogenides,Photogenerated carriers,Two-dimensional materials,Graphene,Charge transfer,Photovoltaic cells
更新于2025-09-23 15:21:01
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Effect of doping mechanism on photogenerated carriers behavior in Cu-doped ZnSe/ZnS/L-Cys core-shell quantum dots
摘要： Cu-doped ZnSe/ZnS/L-Cys core–shell QDs are prepared by both nucleation doping and growth doping in an aqueous synthesis method. Transport of photogenerated free charge carriers (FCCs) in these Cu-doped QDs is probed via a combination of surface photovoltaic (SPV), photoacoustic (PA), and electric-field-induced SPV techniques, supplemented by the UV–VIS absorption spectrum and Raman spectrum. The results confirm that the two doping mechanisms result in different doping locations and microelectronic structures of the Cu-doped QDs. The distinctive microelectronic structure of the QDs prepared by nucleation doping, as compared with those prepared by growth doping, results in a number of favorable SPV characteristics. For example, the QDs prepared by nucleation doping exhibit a higher SPV response intensity at 600 nm because of a higher concentration of photogenerated FCCs. The ratio of the strongest SPV response and the strongest PA signal of the QDs prepared by nucleation doping is up to 2.41 times greater than those of the QDs prepared by growth doping. This is because the greater numbers of photogenerated FCCs in the QDs prepared by nucleation doping generate the PV effect rather than the PA effect that is caused by a nonradiative de-excitation process. The position of the shoulder peak of the SPV response at a long wavelength of the QDs prepared by nucleation doping is significantly red-shifted compared with that of the QDs prepared by growth doping, leading to a broader SPV response range in the visible region. The QDs prepared by nucleation doping have a more obvious donor feature than those prepared by growth doping.
关键词： photogenerated carriers,Cu-doped ZnSe/ZnS/L-Cys,quantum dots,photoacoustic,surface photovoltaic,nucleation doping,growth doping
更新于2025-09-11 14:15:04