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Asymmetrically twisted phenanthrimidazole derivatives as host materials for blue fluorescent, green and red phosphorescent OLEDs
摘要： The electroluminescent properties of asymmetrically twisted phenanthrimidazole derivatives comprised of fluorescent anthracene or pyrene unit namely, 1-(1-(anthracen-10-yl)naphthalen-4-yl)-2-styryl-1H-phenanthro[9,10-d]imidazole (ANSPI), 1-(1-(pyren-1-yl) naphthalene-4-yl)-2-styryl-1H-phenanthro[9,10-d]imidazole (PNSPI), 4-(2-(4-(anthracen-9-yl) styryl)-1H-phenanthro[9,10-d]imidazol-1-yl)naphthalene-1-carbonitrile (ASPINC) and 4-(2-(4-(pyren-1-yl)styryl)-1H-phenanthro[9,10-d] imidazol-1-yl)naphthalene-1-carbonitrile (PSPINC) for blue OLEDs have been analyzed. The asymmetrically twisted conformation interrupt π-conjugation effectively results in deep-blue emission. The pyrene containing PSPINC based non-doped blue device (476 nm) shows maximium efficiencies (current efficiency (ηc)-4.23 cd/A; power efficiency (ηp)-2.86 lm/W; external quantum efficiency (ηex)-3.48%: CIE (0.16, 0.17) at 3.10 V. Among the doped blue devices, An(PPI)2:ASPINC shows high efficiencies (ηc-12.13 cd/A; ηp-5.98 lm/W; ηex-6.79%; L-23986 cd m?2; EL-458 nm) at 3.15 V with CIE (0.15, 0.17) than An(PPI)2:PSPINC based device which is inconsistent with non-doped device performances. The green and red PhOLEDs show higher efficiencies with Ir(ppy)3: ASPINC (ηc-50.6 cd/A; ηp-53.4 lm/W; ηex-17.0%; L-61581 cd m?2; EL-501 nm, CIE (0.31, 0.60) at 3.32 V and (bt)2Ir(dipba): ASPINC (ηc-15.2 cd/A; ηp-16.5 lm/W; ηex-14.5%; L-13456 cd m?2; EL-610 nm), CIE (0.63, 0.36) at 3.20 V, respectively. The complete energy transfer between the host and dopant molecules improved the efficiency of PHOLEDs.
关键词： asymmetrically twisted phenanthrimidazole derivatives,electroluminescent properties,energy transfer,blue OLEDs,deep-blue emission
更新于2025-09-11 14:15:04
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Enhancing Nonradiative Energy Transfer between Nitridized Carbon Quantum Dots and Monolayer WS2
摘要： Two-dimensional (2D) monolayer (1L) transition metal dichalcogenides (TMDs) suffer from a low absorption in the visible light region. Nonradiative energy transfer (NRET) is an effective method to enhance such absorption, which, as shown in this study, can be accomplished by using surface nitridized carbon quantum dots (CQDs). The optical absorption and photoluminescence (PL) of CQDs in the visible light region can be greatly enhanced by increasing the level of nitridization. The nitridized CQDs exhibit weak p-type doping but strong PL quenching in contact with vapor transport (VT)-deposited 1L-WS2. Owing to the good overlap between the fluorescence and absorption spectra for CQDs and 1L-WS2, an interactive NRET process reduces the PL lifetimes of both CQDs and 1L-WS2. The NRET efficiency can be greatly enhanced by up to 73% for samples coated with CQDs of increasing surface nitridization.
关键词： Nonradiative energy transfer,Nitridized carbon quantum dots,Optical absorption,Monolayer WS2,Photoluminescence
更新于2025-09-11 14:15:04
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Exploring Electronic and Excitonic Processes Towards Efficient Deep Red CuInS2/ZnS Quantum-dot Light-emitting Diodes
摘要： The electroluminescence mechanisms in the Cd-free CuInS2/ZnS quantum-dot based light-emitting diodes (QLEDs) are systematically investigated through transient electroluminescence measurements. The results demonstrate that the characteristics of hole transporting layers (HTLs) determine the QLEDs to be activated by the direct charge-injection or the energy-transfer. Moreover, both the energy level alignment between HTL and quantum dot and the carrier mobility properties of the HTLs are critical factors to affect the device performance. By choosing suitable HTL, such as 4,4'-bis(9-carbazolyl)-2,2'-biphenyl, highly efficient deep red (emission peak at ~650 nm) CuInS2/ZnS QLEDs based on single HTL can be obtained with peak current efficiency and luminance of ~2.0 cd/A and nearby 3000 cd/m2, respectively.
关键词： energy transfer,charge injection,hole-transport layer,QLEDs,electron leakage,charge accumulation
更新于2025-09-11 14:15:04
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Theoretical Analysis of Tunable Multimode Coupling in a Grating-Assisted Double-Layer Graphene Plasmonic System
摘要： A double-layer graphene hybrid system is proposed to investigate the multimode coupling at far-infrared frequencies. With the assistance of metallic grating, the upper- and lower-layer graphene surface plasmons as well as the magnetic polaritons can be excited simultaneously, resulting in selective localization of electromagnetic energy. By tuning the thickness of the spacer, the mutual conversion between strong coupling and weak coupling can be achieved, giving rise to hybrid modes and Rabi splitting. The dynamic control of multimode coupling is also investigated via varying the Fermi energy of graphene. The hybrid coupling behaviors exhibit unique energy-transfer and multiband light trapping as well as mode splitting characteristics, which is well described by the classical coupled oscillator model. Our work may inspire related studies on graphene-based light-matter interaction, and the proposed hybrid system provides a good paradigm for designing many plasmonic devices, including tunable optical switches, thermal emitters, multiband absorbers, sensors, etc.
关键词： graphene plasmons,energy-transfer,coupled oscillator model,absorption enhancement,magnetic polaritons
更新于2025-09-11 14:15:04
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Paper sensor of curcumin by fluorescence resonance energy transfer on nitrogen-doped carbon quantum dot
摘要： Paper Sensor detection methods are attractive in wide analytical applications. Presented herein is a paper sensor and ?uorescence methods that was ?rstly developed to detect curcumin (Cur) based on ?uorescence resonance energy transfer (FRET) between nitrogen-doped carbon quantum dots (NCQDs) and Cur. The facile ?uorescent method was demonstrated to detect Cur in the range of 0e2600 mM with a detection limit of 0.13 mM. And facile paper sensor of Cur was fabricated and displayed at concentration of 0 mM, 100 mM, 200 mM, 300 mM, 400 mM, 500 mM and 600 mM, respectively. In additions, it was realized for determination of Cur in real samples including orange juice and curry solution. Compared with the reported methods, the present method is simple, rapid and sensitive for detecting Cur.
关键词： Nitrogen-doped carbon quantum dots (NCQDs),Curcumin (Cur),Fluorescence resonance energy transfer (FRET),Paper-based sensor
更新于2025-09-11 14:15:04
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Precisely Encoded Barcodes Using Tetrapod CdSe/CdS Quantum Dots with a Large Stokes Shift for Multiplexed Detection
摘要： A serious obstacle to the construction of high-capacity optical barcodes in suspension array technology is energy transfer, which can prompt unpredictable barcode signals, limited barcode numbers, and the need for an unfeasible number of experimental iterations. This work reports an effective and simple way to eliminate energy transfer in multicolor quantum dots (QDs)-encoded microbeads by incorporating tetrapod CdSe/CdS QDs with a large Stokes shift (about 180 nm). Exploiting this unique feature enables the facile realization of a theoretical 7 × 7-1 barcoding matrix combining two colors and seven intensity levels. As such, microbeads containing tetrapod CdSe/CdS QDs are demonstrated to possess a powerful encoding capacity which allows for precise barcode design. The ability of the Shirasu porous glass membrane emulsification method to easily control microbead size facilitates the establishment of a 3D barcode library of 144 distinguishable barcodes, indicating the enormous potential to enable large-scale multiplexed detection. Moreover, when applied for the multiplexed detection of five common allergens, these barcodes exhibit superior detection performance (limit of detection: 0.01–0.02 IU mL?1) for both spiked and patient serum samples. Therefore, this new coding strategy helps to expand barcoding capacity while simultaneously reducing the technical and economic barriers to the optical encoding of microbeads for high-throughput multiplexed detection.
关键词： large Stokes shift,F?rster resonance energy transfer (FRET),photon re-absorption,quantum dots-encoded microbeads,multiplexed detection
更新于2025-09-11 14:15:04
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Bimodal velocity distributions in the photodesorption of CO from Si(1 0 0) suggest V-to-T energy transfer
摘要： The photodesorption of CO from Si(1 0 0) has been studied using 355 and 266 nm light obtaining time-of-flight spectra detailing the translation energy released. The spectra clearly exhibit two non-thermal desorption channels, of which one is characterized by an offset energy the size of which is remarkably close to the vibrational quantum of CO. Detailed studies of the spectra as function of coverage and laser fluence used prove that both desorption channels originate from a single adsorbed species. It is suggested that the energy offset is due to vibrational to translational energy transfer along the reaction pathway of the desorbing molecule.
关键词： Photodesorption,Time-of-flight spectra,Vibrational to translational energy transfer,CO,Si(1 0 0)
更新于2025-09-11 14:15:04
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A broadband-sensitive upconverter: garnet-type Ca <sub/>3</sub> Ga <sub/>2</sub> Ge <sub/>3</sub> O <sub/>12</sub> codoped with Er <sup>3+</sup> , Y <sup>3+</sup> , Li <sup>+</sup> , Ni <sup>2+</sup> , and Nb <sup>5+</sup>
摘要： We have developed a new broadband-sensitive photon upconversion (UC) material that can be used for transparent ceramic plates mounted on the rear faces of crystalline silicon solar cells. We selected the host material of a cubic crystal structure codoped with Er3+ and Ni2+ so that the Ni2+ dopants were fully activated to sensitize the Er3+ emitters. In garnet-type Ca3Ga2Ge3O12 with additional codopants of Nb5+ and Li+ for charge compensation, all the Ni2+ dopants occupied the six-coordinated Ga3+ sites, leading to highly efficient energy transfer from the Ni2+ to the Er3+. Formation of four-coordinated Ni2+ that quenches the UC emission of the Er3+ was prevented, because Ni2+ cannot substitute the four-coordinated Ge4+ much smaller than Ni2+. Consequently, energy dissipation from the Er3+ to the Ni2+ was well reduced compared with the previously developed Gd3Ga5O12:Er,Ni,Nb in which the Ni2+ dopants partially occupied the four-coordinated Ga3+ sites. Additional introduction of Y3+ and Li+ enhanced optical transitions and improved the UC performance, owing to more enhanced lattice distortion, along with eliminating different phases. The optimal composition (Ca0.6Er0.1Y0.1Li0.2)3(Ga0.98Ni0.01Nb0.01)2Ge3O12 exhibited a broadband sensitivity ranging from 1.1 μm (the absorption edge of silicon) to 1.6 μm for the UC emission at 0.98 μm.
关键词： solar cell,photoluminescence,up-conversion,erbium/erbium compounds,energy transfer
更新于2025-09-11 14:15:04
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Effect of High Pressure in the Luminescence of Pr <sup>3+</sup> Doped Ge <sub/>2</sub> O- PbO Glass Containing Au Nanoparticles
摘要： In this paper it was investigated the combined effect of gold nanoparticles and high-pressure densification on the luminescence of Pr3+ doped heavy metal GeO2-PbO photonic glass. Localized states related to ion-trapped exciton defects, S1 and S2, were observed at 342 and 412 nm before densification. After densification under 7.7 GPa the structure of the glass host changed irreversibly, as indicated by the infrared spectrum, refractive index and density measurements. TEM analyses indicated that the high-pressure densification induced the formation of clusters of gold nanoparticles. The modifications observed in the absorption and luminescence spectra of Pr3+ ions in the VIS-NIR range were associated to the changes in the local field surrounding the Pr3+ ions in the host glass induced by high-pressure. For excitation at 445 nm (luminescence from 3P2) and 593 nm (luminescence from 1D2), the combined effect of densification and gold nanoparticles induced an increase in the emission band at 1050 cm-1. For excitation at 488 nm (luminescence from 3P0), the combined effect resulted in a strong decrease in the emission intensities in the VIS, revealing the emergence of non-radiative processes in resonance with 3P0 state. The observed behavior was probably due to energy transfer, ion trapped exciton defects and cross-relaxation processes among the Pr3+ ions and gold nanoparticles.
关键词： cross-relaxation processes,gold nanoparticles,Pr3+ doped,high-pressure densification,energy transfer,GeO2-PbO glass,luminescence
更新于2025-09-11 14:15:04
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Simulations of Frenkel to Wannier-Mott-Exciton Transitions in a Nano-Hybrid System
摘要： Excitation energy transfer at a prototypical organic/inorganic interface is described theoretically. The nano-hybrid system to be investigated is built up by a vertical stacking of 20 para-sexiphenyl molecules physisorbed on a ZnO nano-crystal of 3903 atoms. To determine the time scale of excitation energy transfer all relevant electronic excitations of the organic and inorganic part are computed together with the related excitation energy transfer couplings. Values of the coupling lie in the meV-range or less. This motivates a Golden Rule description of the excitation energy transfer. Different Frenkel excitons are chosen as excitation energy donor levels. Due to the H-aggregate configuration of the organic part the number of exciton wave function nodes increases with decreasing exciton energy. As a result, the couplings of the individual molecules to a certain ZnO electron-hole pair cancel each other more intensively and the overall transfer rate gets smaller. The highest exciton levels decay most rapidly and are characterized by lifetimes in the ps-region. The lower part of the exciton band, however, has lifetimes in the ns-region. The Golden Rule description is finally compared to a direct solution of the time-dependent Schroedinger equation. The obtained transfer dynamics confirm those of the rate equation approach when the higher part of the Frenkel exciton band is considered. In the lower part the reduced number of final electron-hole pair states in the inorganic part blocks the Frenkel-exciton decay.
关键词： nano-hybrid system,Golden Rule,Frenkel excitons,time-dependent Schroedinger equation,Wannier-Mott excitons,Excitation energy transfer
更新于2025-09-11 14:15:04