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Understanding Spatiotemporal Photocarrier Dynamics in Monolayer and Bulk MoTe <sub/>2</sub> for Optimized Optoelectronic Devices
摘要： Semiconducting molybdenum ditelluride has emerged as a promising transition-metal dichalcogenide with a number of novel properties. In particular, its bandgap in infrared range makes it an attractive candidate for ultrathin and high-performance infrared optoelectronic applications. Dynamical properties of photocarriers play a key role in determining performance of such devices. We report an experimental study on spatiotemporal dynamics of photocarriers in both monolayer and bulk MoTe2. Transient absorption measurement in reflection geometry revealed ultrafast thermalization and relaxation processes of photocarriers and lifetimes of about 60 and 80 ps in monolayer and bulk MoTe2, respectively. By spatially resolved transient absorption measurements on monolayer, we obtained an exciton diffusion coefficient of 20 ± 10 cm2 s?1, a mean free time of 200 fs, a mean free path of 20 nm, and a diffusion length of 350 nm. The corresponding values for the bulk sample are 40 ± 10 cm2 s?1, 400 fs, 40 nm, and 570 nm, respectively. These results provide fundamental information for understanding and optimizing performance of MoTe2-based optoelectronic devices.
关键词： two-dimensional material,exciton,transient absorption,molybdenum ditelluride,transition-metal dichalcogenide,diffusion,photocarrier dynamics
更新于2025-09-23 15:23:52
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Photocarrier relaxation pathway in selenium quantum dots and its application for UV-Vis photodetecting
摘要： Chain-like materials have recently attracted significant attention due to their unique structure and outstanding electro-optical properties. However, the photocarrier dynamics and pathways in these materials that determine the electro-optical performances of the prepared devices have barely been touched. Herein, one typical chain-like materials e quantum dots (Se QDs) were prepared via a facile liquid phase exfoliation approach. The photocarrier dynamics in selenium quantum dots were systematically investigated via ultrafast transient absorption spectroscopy in the ultraviolet-visible regime. Four photocarrier decay pathways with different lifetime times were firstly detected, endues the elucidation and reconstruction of the energy schematic diagram of Se QDs. Thanks to the broadband photo-response and fast recovery time of Se QDs, a photoelectrochemical (PEC)-typed photodetector was proposed for the first time to our knowledge, demonstrating excellent photodetection properties. Considering the feasible fabrication method and clear photocarrier pathways, the excellent photocurrent density and stability of this photodetector undoubtedly guarantee the promising of selenium for advanced photonics devices.
关键词： broadband photo-response,photocarrier dynamics,ultrafast transient absorption spectroscopy,selenium quantum dots,photoelectrochemical photodetector
更新于2025-09-23 15:19:57
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Implementation of data-cube pumpa??probe KPFM on organic solar cells
摘要： An implementation of pump–probe Kelvin probe force microscopy (pp-KPFM) is reported that enables recording the time-resolved surface potential in single-point mode or over a 2D grid. The spectroscopic data are acquired in open z-loop configuration, which simplifies the pp-KPFM operation. The validity of the implementation is probed by measurements using electrical pumping. The dynamical photoresponse of a bulk heterojunction solar cell based on PTB7 and PC71BM is subsequently investigated by recording point-spectroscopy curves as a function of the optical power at the cathode and by mapping 2D time-resolved images of the surface photovoltage of the bare organic active layer.
关键词： Kelvin probe force microscopy (KPFM),time-resolved measurements,bulk heterojunctions,organic photovoltaics,pump–probe configuration,photocarrier dynamics
更新于2025-09-16 10:30:52
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Observation of charge transfer in mixed-dimensional heterostructures formed by transition metal dichalcogenide monolayers and PbS quantum dots
摘要： We report an experimental study on charge transfer properties of mixed-dimensional heterostructures formed by zero-dimensional PbS quantum dots and two-dimensional transition metal dichalcogenides. Monolayers of MoSe2 and MoS2 were fabricated by mechanical exfoliation and chemical vapor deposition techniques, respectively. PbS quantum dots with diameters of 2.3 and 5 nm were synthesized by a hot-injection method and characterized by optical absorption spectroscopy and ultraviolet photoemission spectroscopy. The quantum dots were deposited on the MoS2 and MoSe2 monolayers to form heterostructures. Photoluminescence and transient absorption measurements were performed on the heterostructures as well as individual materials to reveal their photocarrier dynamics. We found that the holes excited in MoSe2 can efficiently transfer to both 2.3- and 5-nm PbS quantum dots, while electrons in these quantum dots cannot transfer to MoSe2. Similar charge transfer properties were observed between MoS2 and the 5-nm PbS quantum dots, while no charge transfer was observed between MoS2 and the 2.3-nm quantum dots. These results provide useful information for understanding the physical mechanism of charge transfer in mixed-dimensional heterostructures and for developing PbS quantum-dot-based mixed-dimensional materials.
关键词： PbS quantum dots,mixed-dimensional heterostructures,transition metal dichalcogenides,photocarrier dynamics,charge transfer
更新于2025-09-12 10:27:22