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排序方式： 共有139条查询结果，搜索用时 15 毫秒
11.
Golam Haider Krishna Sampathkumar Tim Verhagen Lukáš Nádvorník Farjana J. Sonia Václav Valeš Jan Sýkora Peter Kapusta Petr Němec Martin Hof Otakar Frank Yang-Fang Chen Jana Vejpravová Martin Kalbáč 《Advanced functional materials》2021,31(29):2102196
Recent advancements in isolation and stacking of layered van der Waals materials have created an unprecedented paradigm for demonstrating varieties of 2D quantum materials. Rationally designed van der Waals heterostructures composed of monolayer transition-metal dichalcogenides (TMDs) and few-layer hBN show several unique optoelectronic features driven by correlations. However, entangled superradiant excitonic species in such systems have not been observed before. In this report, it is demonstrated that strong suppression of phonon population at low temperature results in a formation of a coherent excitonic-dipoles ensemble in the heterostructure, and the collective oscillation of those dipoles stimulates a robust phase synchronized ultra-narrow band superradiant emission even at extremely low pumping intensity. Such emitters are in high demand for a multitude of applications, including fundamental research on many-body correlations and other state-of-the-art technologies. This timely demonstration paves the way for further exploration of ultralow-threshold quantum-emitting devices with unmatched design freedom and spectral tunability. 相似文献
12.
Christopher C. S. Chan Chao Ma Xinhui Zou Zengshan Xing Guichuan Zhang Hin-Lap Yip Robert A. Taylor Yan He Kam Sing Wong Philip C. Y. Chow 《Advanced functional materials》2021,31(48):2107157
Transient optical spectroscopy is used to quantify the temperature-dependence of charge separation and recombination dynamics in P3TEA:SF-PDI2 and PM6:Y6, two non-fullerene organic photovoltaic (OPV) systems with a negligible driving force and high photocurrent quantum yields. By tracking the intensity of the transient electroabsorption response that arises upon interfacial charge separation in P3TEA:SF-PDI2, a free charge generation rate constant of ≈2.4 × 1010 s−1 is observed at room temperature, with an average energy of ≈230 meV stored between the interfacial charge pairs. Thermally activated charge separation is also observed in PM6:Y6, and a faster charge separation rate of ≈5.5 × 1010 s−1 is estimated at room temperature, which is consistent with the higher device efficiency. When both blends are cooled down to cryogenic temperature, the reduced charge separation rate leads to increasing charge recombination either directly at the donor-acceptor interface or via the emissive singlet exciton state. A kinetic model is used to rationalize the results, showing that although photogenerated charges have to overcome a significant Coulomb potential to generate free carriers, OPV blends can achieve high photocurrent generation yields given that the thermal dissociation rate of charges outcompetes the recombination rate. 相似文献
13.
《Advanced Materials Interfaces》2018,5(13)
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. 相似文献
14.
Rui Wang Xiantao Jiang Siyan Gao Jinlai Zhao Feng Zhang Weichun Huang Taojian Fan Weiyuan Liang Zhongjun Li Hao Huang Zhinan Guo Huide Wang Yupeng Zhang Xi Zhang Zhengqian Luo Han Zhang 《Advanced Materials Interfaces》2019,6(13)
In contrast to zero‐bandgap metallic graphene, the binary semiconducting compound, InSe, possesses a tunable bandgap. Herein, a range of particle sizes of β‐InSe from bulk to few‐layer nanosheets and quantum dots are carefully prepared. The size‐dependent bandgap variation and photon‐induced carrier dynamics of InSe are systemically investigated. In contrast to the normal size‐dependent carrier lifetime trend observed at 700 nm, anomalous size‐independent carrier decay is observed at 500 nm. Through time‐dependent density functional theory calculations, the normal carrier lifetimes at lower probe photon energies are attributed to in‐plane excitons, whereas the abnormal size‐independent carrier lifetimes at higher probe photon energies are found to be stimulated by surface‐bound excitons. In view of the robust surface exciton, this suggests that InSe may possess an outstanding optoelectronic performance in the shorter wavelength range. Through photoelectrochemical detection experiments, it is confirmed that InSe features a high photocurrent density and stability and, in particular, a more distinct photoresponse at short wavelengths than at longer ones. Comprehending and quantifying the role of the surface‐bound excitons in InSe across a broad range of semiconductor nanostructures and their fundamental properties may play an important role in understanding the physical properties of 2D III–VI compound materials. 相似文献
15.
Romain Gautier Florian Massuyeau Gabin Galnon Michael Paris 《Advanced materials (Deerfield Beach, Fla.)》2019,31(14)
Hybrid metal halides containing perovskite layers have recently shown great potential for applications in solar cells and light‐emitting diodes. Such compounds exhibit quantum confinement effects leading to tunable optical and electronic properties. Thus, broadband white‐light emission has been observed from diverse metal halides and, owing to high color rendering index, high thermal stability, and low‐temperature solution processability, these materials have attracted interest for application in solid‐state lighting. However, the reported quantum yields for white photoluminescence (PLQY) remain low (i.e., in the range 0.5–9%) and no approach has shown to successfully increase the intensity of this emission. Here, it is demonstrated that the quantum efficiencies of hybrid metal halides can be greatly enhanced if they contain a polymorph of the [PbX4]2? perovskite‐type layers: the [PbX4]2? post‐perovskite‐type chains showing a PLQY of 45%. Different piperazines lead to a hybrid lead halide with either perovskite layers or post‐perovskite chains influencing strongly the presence of self‐trapped states for excitons. It is anticipated that this family of hybrid lead halide materials could enhance all the properties requiring the stabilization of trapped excitons. 相似文献
16.
With the ability to produce large amounts of purely semiconducting and even monochiral dispersions of single‐walled carbon nanotubes (SWCNT) their application as a bulk material in thin film devices on a large scale becomes feasible. Their physical properties, processing, and final devices are quite similar to those of semiconducting polymers. In the extreme case one may view carbon nanotubes as very long, rigid, and fully conjugated polymers. This analogy raises the question whether the knowledge accumulated over the last two decades of processing and studying conjugated polymers could be transferred to solution‐processed nanotube devices. Here, the optical and electronic properties of both materials in solution and in thin films are discussed and compared with a focus on their application in optoelectronic devices. Some striking similarities and common issues are highlighted to show the connection between conjugated polymers and SWCNTs as 1D semiconductors. 相似文献
17.
Yingzhi Jin Yanxin Zhang Yanfeng Liu Jie Xue Weiwei Li Juan Qiao Fengling Zhang 《Advanced materials (Deerfield Beach, Fla.)》2019,31(22)
Organic photovoltaic cells (OPVs) have attracted broad attention and become a very energetic field after the emergence of nonfullerene acceptors. Long‐lifetime triplet excitons are expected to be good candidates for efficiently harvesting a photocurrent. Parallel with the development of OPVs based on singlet materials (S‐OPVs), the potential of triplet materials as photoactive layers has been explored. However, so far, OPVs employing triplet materials in a bulk heterojunction have not exhibited better performance than S‐OPVs. Here, the recent progress of representative OPVs based on triplet materials (T‐OPVs) is briefly summarized. Based on that, the performance limitations of T‐OPVs are analyzed. The shortage of desired triplet materials with favorable optoelectronic properties for OPVs, the tradeoff between long lifetime and high binding energy of triplet excitons, as well as the low charge mobility in most triplet materials are crucial issues restraining the efficiencies of T‐OPVs. To overcome these limitations, first, novel materials with desired optoelectronic properties are urgently demanded; second, systematic investigation on the contribution and dynamics of triplet excitons in T‐OPVs is necessary; third, close multidisciplinary collaboration is required, as proved by the development of S‐OPVs. 相似文献
18.
P. D. Altukhov 《Journal of Superconductivity》2003,16(2):267-270
A recombination radiation line of real excitons in dense two-dimensional electron gas at the [100] silicon surface is observed in luminescence spectra of metal-oxide-semiconductor (MOS) structures. A new effect of anisotropic paramagnetic reduction of the luminescence line indicates a strong influence of the Kondo correlations on electron paramagnetism of the excitons. 相似文献
19.
R. J. Almassy D. C. Reynolds C. W. Litton K. K. Bajaj D. C. Look 《Journal of Electronic Materials》1978,7(2):263-277
Magneto-optical analysis of prominent photoluminescence lines from GaAs FET structures has been performed. Fifteen samples
were investigated. Each consisted of a sulfur doped active layer on a high resistivity buffer layer (both epitaxially grown
films) on a chromium doped GaAs substrate. The active layers were generally 2μm thick or less, except for two thicker layers
(4 and 5μm) grown especially for this study. Buffer layer thicknesses ranged from 1.5 to 26μm. A model based on carrier diffusion
through the active layer has been used to interpret the spectra as originating from the active-buffer interface region. All
spectra contain strong-evidence of two donorbound exciton complexes associated with sulfur (1.51417eV) and silicon (1.51412eV).
Other sharp spectral features included up to six lines associated with more complicated complexes. Linear Zeeman and quadratic
diamagnetic behavior of the lines in applied magnetic fields are discussed.
Supported under AF Contract F33615-77-C-5003
Supported under AF Contract F33615-76-C-1207 相似文献
20.
David Beljonne Zhigang Shuai AiJun Ye Jean‐Luc Brdas 《Journal of the Society for Information Display》2005,13(5):419-427
Abstract— An overview of our recent work on the mechanisms of singlet and triplet exciton formation in electroluminescent π‐conjugated materials will be presented. According to simple spin statistics, only one‐fourth of the excitons are formed as singlets. However, deviations from that statistics can occur if the initially formed triplet charge‐transfer (CT) excited states are amenable to intersystem crossing or dissociation. Although the electronic couplings between the CT states and the neutral exciton states are expected to be largest for the lowest singlet and triplet excitons (S1 and T1, respectively), the possibility for direct recombination into T1 is always very small due to the large exchange energy. In small molecules, spin statistics is expected to be observed because both singlet and triplet exciton formations proceed via higher‐lying Sn/Tn states with similar electronic couplings and fast formation rates. In extended conjugated chains, however, that the 1CT → S1 pathway is faster while the 3CT → Tn channels become much slower, opening the route to intersystem crossing or dissociation among the 3CT states. 相似文献