Colloidal PbS nanoplatelets (NPLs) are highly interesting materials for near-infrared optoelectronic applications. We use ultrafast transient optical absorption spectroscopy to study the characteristics and dynamics of photoexcited excitons in ultrathin PbS NPLs with a cubic crystal structure. NPLs are synthesized at near room temperature from lead oleate and thiourea precursors; they show an optical absorption onset at 680 nm (1.8 eV) and photoluminescence at 720 nm (1.7 eV). By postsynthetically treating PbS NPLs with CdCl, their photoluminescence quantum yield is strongly enhanced from 1.4% to 19.4%. The surface treatment leads to an increased lead to sulfur ratio in the structures and associated reduced nonradiative recombination. Additionally, exciton-phonon interactions in pristine and CdCl treated NPLs at frequencies of 1.96 and 2.04 THz are apparent from coherent oscillations in the transient absorption spectra. This study is an important step forward in unraveling and controlling the optical properties of IV-VI semiconductor NPLs.
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http://dx.doi.org/10.1021/acs.jpclett.0c03461 | DOI Listing |
Nanoscale
January 2025
School of Chemical Sciences, National Institute of Science Education and Research (NISER), Bhubaneswar, Odisha 752050, India.
The performance of an optoelectronic device is largely dependent on the light harvesting properties of the active material as well as the dynamic behaviour of the photoexcited charge carriers upon absorption of light. Recently, atomically thin two-dimensional transition metal dichalcogenides (2D TMDCs) have garnered attention as highly prospective materials for advanced ultrathin solar cells and other optoelectronic applications, owing to their strong interaction with electromagnetic radiation, substantial optical conductivity, and impressive charge carrier mobility. WSe is one such extremely promising solar energy material.
View Article and Find Full Text PDFLangmuir
January 2025
Key Laboratory of Photonic Materials and Devices Physics for Oceanic Applications, Ministry of Industry and Information Technology of China, College of Physics and Optoelectronic Engineering, Harbin Engineering University, Harbin 150001, China.
Due to intrinsic defects in blue-light-emitting perovskite materials, the charge carriers are prone to being trapped by the trap states. Therefore, the preparation of efficient blue-light-emitting perovskite materials remains a significant challenge. Herein, CsPb(Cl/Br) nanocrystal (NCs)@SiO structures were fabricated through hydrolyzing (3-aminopropyl)-triethoxysilane (APTS).
View Article and Find Full Text PDFAdv Mater
December 2024
School of Nano-Tech and Nano-Bionics, University of Science and Technology of China, Hefei, Anhui, 230026, P. R. China.
Monolayer transition metal dichalcogenides (TMDs) with strong exciton effects have enabled diverse light emitting devices, however, their Ångstrom thickness makes it challenging to efficiently manipulate exciton emission by themselves. Although their nanostructured multi-layer counterparts can effectively manipulate optical field at deep subwavelength thickness scale, these indirect band gap multi-layer TMDs are lack of strong luminescence, hindering their applications in light emitting devices. Here, the integration of monolayer TMDs is presented with nanostructured multi-layer TMDs, combining both strong exciton emission and optical manipulation in a single ultra-thin platform.
View Article and Find Full Text PDFNanophotonics
July 2024
Department of Applied Physics and Eindhoven Hendrik Casimir Institute, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands.
Two-dimensional materials give access to the ultimate physical limits of photonics with appealing properties for ultracompact optical components such as waveguides and modulators. Specifically, in monolayer semiconductors, a strong excitonic resonance leads to a sharp oscillation in permittivity from positive to even negative values. This extreme optical response enables surface exciton-polaritons to guide visible light bound to an atomically thin layer.
View Article and Find Full Text PDFNanophotonics
March 2024
Department of Physics, Hanyang University, Seoul 04763, Korea.
Transition metal dichalcogenide (TMDs) heterostructure, particularly the lateral heterostructure of two different TMDs, is gaining attention as ultrathin photonic devices based on the charge transfer (CT) excitons generated at the junction. However, the characteristics of the interface of the lateral heterostructure, determining the electronic band structure and alignment at the heterojunction region, have rarely been studied due to the limited spatial resolution of nondestructive analysis systems. In this study, we investigated the confined phonons resulting from the phonon-disorder scattering process involving multiple disorders at the lateral heterostructure interface of MoS-WS to prove the consequences of disorder-mediated deformation in the band structure.
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