- 标题
- 摘要
- 关键词
- 实验方案
- 产品
过滤筛选
- 2019
- 2018
- light-emitting diode
- light distribution
- optical lens
- Monte Carlo raytracing
- road lighting
- optimization
- Inorganic perovskite quantum dots
- Stability
- Light-emitting diodes
- Light Source and Lighting
- Optoelectronic Information Materials and Devices
- Technical University of Gabrovo
-
Monodisperse Six-Armed Starbursts based on Truxene-Cored Multibranched Oligofluorenes: Design, Synthesis, and Stabilized Lasing Characteristics
摘要： A series of monodisperse six-armed conjugated starbursts (Tr1F, Tr2F and Tr3F) containing a truxene core and multibranched oligofluorene bridges capped with diphenylamine (DPA) units has been designed, synthesized, and investigated as robust gain media for organic semiconductor lasers (OSLs). The influence of electron-rich DPA end-groups on their optoelectronic characteristics has been discussed at length. DPA cappers effectively raise HOMO levels of the starbursts, thus enhancing the hole injection and transport ability. Solution-processed electroluminescence devices based on the resulting six-armed starbursts exhibited efficient deep-blue electroluminescence with clear reduced turn-on voltages (3.2~3.5 V). Moreover, the resulting six-armed molecules showed stabilized electroluminescence and amplified spontaneous emission with low thresholds (27.4~63.9 nJ pulse-1), high net gain coefficients (80.1~101.3 cm-1), and small optical loss (2.6~4.4 cm-1). Distributed feedback OSLs made from Tr3F exhibited low lasing threshold of 0.31 kW/cm2 (at 465 nm). The results suggest that the construction of truxene-centered six-armed conjugated starbursts with the incorporation of DPA units can effectively enhance EL properties by precisely regulating the HOMO energy levels, and further optimizing their optical gain properties.
关键词： Organic gain media,Organic light-emitting diodes (OLEDs),Conjugated starburst molecules,Organic semiconductor lasers (OSLs),HOMO levels
更新于2025-09-23 15:22:29
-
Ultraviolet electroluminescence from nanostructural SnO2-based heterojunction with high-pressure synthesized Li-doped ZnO as a hole source
摘要： We report an ultraviolet (UV) electroluminescence (EL) in n-SnO2/p-ZnO heterojunction light-emitting diodes with the nanostructural SnO2 as an n-type layer and the Li-doped ZnO (ZnO:Li) synthesized by high-temperature high-pressure (HTHP) method as a high hole concentration p-type layer. Two kinds of SnO2 nanostructures including nanobelts (NBs) and nanowires (NWs) were used to fabricate n-type layers in the heterojunctions. The two heterojunctions with different SnO2 nanostructures demonstrate different light-emission feature in EL measurements. The SnO2 NBs/p-ZnO heterojunction shows a blue emission band centered at 416 nm under forward-bias voltage. A strong UV emission peak located at 391 nm was observed for the SnO2 NWs/p-ZnO heterojunction. Photoluminescence (PL) spectra indicate that the difference in EL is attributed to morphology-dependent light-emission feature in nanostructural SnO2 layer. Our results suggest that the nanostructural SnO2/ZnO:Li heterojunction is a potential and promising system in the UV optoelectronic field.
关键词： High-temperature high-pressure method,Light-emitting diode,Nanobelt,Nanowire,SnO2,Li-doped ZnO
更新于2025-09-23 15:22:29
-
Photomedicine - Advances in Clinical Practice || Light-Emitting Woven Fabric for Treatment with Photodynamic Therapy and Monitoring of Actinic Keratosis
摘要： A successful photodynamic therapy (PDT) requires a specific photosensitizer, oxygen and light of a specific wavelength and power. Today photodynamic therapy (PDT) is administered to patients with light-emitting diode (LED) panels. These panels deliver a non-uniform light distribution on the human body parts, as the complex human anatomy is not a flat surface (head vertex, hand, shoulder, etc.). For an efficient photodynamic therapy (PDT), a light-emitting fabric (LEF) was woven from plastic optical fibers (POF) aiming at the treatment of dermatologic diseases such as actinic keratosis (AK). Plastic optical fibers (POF) (Toray, PGR-FB250) have been woven in textile in order to create macro-bendings, and thus emit out the injected light directly to the skin. The light intensity and light-emitting homogeneity of the LEF were improved thanks to Doehlert Experimental Design. During the treatment with PDT, the photosensitizers were activated in the cancerous cells. These cells may be visualized, as they show a characteristic fluorescence under UV light, which is called fluorescence diagnosis (FD). Therefore, it is proposed to modify the developed LEF for PDT to measure the fluorescence amount. For this aim, a part of POFs was cut out to observe the quantity of light that could be collected while the LEF was connected to a light source. The first prototypes showed the possibility of the illumination with the same LEF without losing the efficiency but also imaging the collected light.
关键词： fluorescence diagnosis (FD),weaving,light emitting fabric (LEF),plastic optical fiber (POF),photodynamic therapy (PDT)
更新于2025-09-23 15:22:29
-
Carbazole based ionic small molecule emitter for non-doped light-emitting electrochemical cells
摘要： Great efforts have been made to develop blue emitting organic small molecules for light-emitting electrochemical cells. Herein, blue emitting CPC (CarPhenCar) was synthesized and its emissive properties were studied. CPC exhibits blue fluorescence in toluene solution as well as in solid thin-films. CPC exhibits good thermal and electrochemical stabilities. Application of CPC molecule in solution processed light-emitting electrochemical cells resulted blue emission centered at 485 nm with brightness of 454 cd/m2, current efficiencies of 1.33 cd/A and external quantum efficiencies of 1.76%. These results adequately demonstrate the practicability of tuning the emission color of phenothiazine derivative into blue region.
关键词： Small molecule,ionic,light-emitting electrochemical cells,blue fluorescence
更新于2025-09-23 15:22:29
-
Indoor Localization Using K-Pairwise Light Emitting Diode Image-Sensor-Based Visible Light Positioning
摘要： A great deal of research has been devoted to studying indoor localization schemes for the development of location-based services. This study investigated an indoor localization system, including subsystems of non-line-of-sight (NLOS) image-sensor-based visible light communications (IS-VLC) and the proposed ??-pairwise light emitting diode (LED) image-sensor-based visible light positioning (IS-VLP), in a unified lighting environment. A smartphone received multiple LED identifiers through the designed NLOS IS-VLC and successfully performed the proposed ??-pairwise LED IS-VLP with ?? = 3 to achieve localization, with maximum localization errors of 2.92 cm and 3.54 cm being obtained for ceiling heights of 100 cm and 150 cm, respectively.
关键词： visible light communications (VLC),Image-sensor-based visible light positioning (VLP),light emitting diode (LED)
更新于2025-09-23 15:21:21
-
Simple molecular-engineering approach for enhancing orientation and out-coupling efficiency of thermally activated delayed fluorescent emitters without red-shifting emission
摘要： The inclusion of a tetraphenylbenzene (4Ph) unit in thermally activated delayed fluorescence (TADF) emitters is demonstrated as a novel strategy for greatly enhancing the horizontally oriented alignment of the emitters without shifting the emission spectrum to longer wavelengths. Doping of blue-emitting 4PhOXDDMAC or greenish-blue-emitting 4PhOXDPXZ into o-DiCbzBz host layers yielded much higher degrees of horizontally oriented alignment for the emitter (up to 92%) compared to when the 4Ph unit was excluded (69% and 75%, respectively). The enhanced alignment results in high out-coupling efficiencies of 24% and 35% in organic light-emitting diodes based on 4PhOXDDMAC and 4PhOXDPXZ, respectively, and boosts the external quantum efficiencies to values (8.8% and 29.2%, respectively) that are higher than would be expected for randomly oriented emitters (out-coupling efficiency of 20%). These enhancements are achieved while avoiding the red-shift that often occurs using the common strategy of increasing molecular length, and, thereby, conjugation, to increase orientation.
关键词： transition dipole moment,thermally activated delayed fluorescence,light out-coupling factor,molecular orientation,organic light-emitting diodes
更新于2025-09-23 15:21:21
-
Impact of Random Receiver Orientation on Visible Light Communications Channel
摘要： Visible Light Communications (VLC) has been studied thoroughly in recent years as an alternative or complementary technology to radio frequency communications. The reliability of VLC channels highly depends on the availability and alignment of line of sight links. In this work, we study the effect of random receiver orientation for mobile users over VLC downlink channels, which affects the existence and quality of line of sight links. Based on the statistics of the receiver location and relative orientation with respect to the transmitter LED, we develop an analytical framework to characterize the statistical distribution of VLC downlink channels, which is then utilized to obtain the outage probability and the bit error rate. Our analysis is generalized for arbitrary distributions of relative orientation and location for a single transmitter, and extended to multiple transmitter case for some certain scenarios. Extensive Monte Carlo simulations show a perfect match between the analytical and the simulation data in terms of both the statistical channel distribution and the resulting bit error rate. Our results also characterize the channel attenuation due to random receiver orientation and location for various scenarios of interest.
关键词： probability,random variables,Light-emitting diodes,optical communication,light-fidelity (Li-Fi)
更新于2025-09-23 15:21:21
-
Dimming Control Systems Based on Low-PAPR SCFDM for Visible Light Communications
摘要： In this paper, the efficient dimming control systems based on single-carrier frequency-division multiplexing (SCFDM) are proposed for visible light communications (VLC). By virtue of the strengths of the low peak-to-average power ratio and the inherent resistance to high-frequency distortion, the proposed SCFDM-based dimming control schemes are adaptive to the bandwidth-limited and linearity-limited VLC system, thus supporting the wide dimming range for different illumination requirements. Two SCFDM-based VLC systems with dimming control including asymmetrical hybrid optical SCFDM (AHO-SCFDM) and DC-biased optical SCFDM (DCO-SCFDM) are proposed. For AHO-SCFDM with spectral efficiency of 1.75 bit/s/Hz and DCO-SCFDM with spectral efficiency of 2 bit/s/Hz, the 20% wider dimming range can be achieved than their orthogonal frequency-division multiplexing (OFDM) based counterparts, respectively. Meanwhile, the two proposed schemes can also achieve 24.8% and 31.3% gains of average spectral efficiency under the same dimming range compared with their counterparts, respectively. For an overall analysis, SCFDM shows the feasibility and superiority for dimming control systems.
关键词： light emitting diode,Visible light communication,single-carrier frequency-division multiplexing,dimming control,orthogonal frequency-division multiplexing
更新于2025-09-23 15:21:21
-
[IEEE 2018 VII. Lighting Conference of the Visegrad Countries (Lumen V4) - Trebic, Czech Republic (2018.9.18-2018.9.20)] 2018 VII. Lighting Conference of the Visegrad Countries (Lumen V4) - Evaluation of Lighting Parameters at the Workplace with the use Replacements for Incandescent Lamps
摘要： The article evaluates the possibility of using halogen lamps, compact fluorescent lamps and LED lamps as direct substitutes of traditional 100 W incandescent lamps for selected residential lighting applications. A single halogen lamp, six compact fluorescent lamps and six LED light sources were examined. A traditional light bulb was also examined for comparison. All lamps operated in three luminaires. The basic evaluation criterion was the illuminance, uniformity and glare limitation in the place of work. It was found that not all light sources can be considered substitutes of traditional light bulbs. In the case of a luminaire made from a translucent material and one luminaire with a reflector, not all lamps allowed to obtain at least the same lighting parameters in the place where visual work was performed, as when a traditional light bulb was used.
关键词： light-emitting diode (LED),bulb's replacement,lighting parameters at the workplace,light sources for household
更新于2025-09-23 15:21:21
-
Increased luminescent efficiency of perovskite light emitting diodes based on modified two-step deposition method providing gradient concentration
摘要： We increased the luminescent efficiency of perovskite light-emitting diodes (PeLEDs) by using a modified two-step deposition method combined with an interdiffusion process without additional solvent engineering or additive molecules. Methylammonium lead bromide (MAPbBr3) polycrystalline films with nanosized grains and low electronic disorder were fabricated by a modified two-step deposition process. The as-fabricated MAPbBr3 films showed gradient concentration characteristics as a result of a gradient distribution of the MABr. Also, the MABr-gradient concentration structure was intensified by the interdiffusion process, showing improved performance of MAPbBr3 PeLEDs with maximum current efficiency CEmax = 0.861 cd A?1 and maximum luminance = 604 cd m?2 with very narrow electroluminescence spectral width. This is the highest CEmax among MAPbBr3-based PeLEDs deposited by the two-step deposition method.
关键词： two-step deposition method,perovskite light-emitting diodes,luminescent efficiency,gradient concentration,interdiffusion process
更新于2025-09-23 15:21:21