Search

A suitable model for OLED simulation is provided. We included the tail state model, field dependent model, and triplet conversion model at heterojunction interface into our developed simulator to provide academic free TCAD simulator for research society. The details of simulator, algorithm, and fitting to experimental results will be provided.

We propose novel dimmable sunlight-like white organic light-emitting diodes that were fabricated using three luminophores to form an emitting spectrum similar to black body radiation at 2250 K with ultra-high color rendering index (CRI) value of 91, which nearly remained the constant at various luminance values ranging from 100 to more than 2500 cd/m 2 at Commission Internationale de l’Eclairage chromaticity coordinates of (0.51, 0.41). Introducing charge modification layers suppressed the energy transfer between the emitting material layers and increased the probability of carrier recombination. Moreover, we reveal that covering long-wavelength ranges played a vital role in achieving high CRI values; the CRI values of a spectrum artificially shifted toward a long-wavelength direction (from 610 to 620 nm) remained constant, whereas those of a spectrum shifted toward a short-wavelength direction (from 610 to 600 nm) dropped to 79.

The emission properties of an organic layer embedded in a metal–organic–metal (MOM) structure were investigated. A partially radiative odd-SPW as well as a non-radiative even-SPW modes are supported by hybridization of the SPW modes on the opposite organic/metal interface in the structure. Because of the competition by this radiative SPW, the population of excitons that recombine to form non-radiative SPW should be reduced. This may account for why the photoluminescence intensity of the MOM sample is higher than that of an organic–metal sample even though the MOM sample has an additional metal layer that should intuitively act as a filter.

In this paper, we discuss an approach to fabricating a carbon nanotubes (CNTs) gate electrode structure for cold cathode emitter applications. The field emission behavior of the structure was studied by using single vertically aligned free-standing CNTs of various lengths and gate electrodes of various sizes to determine the optimal emission structure. A single CNT electrode source with a gate electrode was fabricated by combining optical lithography, electron-beam lithography (EBL), and inductively coupled plasma chemical vapor deposition (ICP-CVD). A single mask was adopted to define the gated structure and nano sized catalyst for CNT growth. A vertically aligned CNT was then grown within the gate hole by ICP-CVD. The CNT height inside the gate could be lengthened by multiple growth processes without affecting the field emission capability. The best turn-on fields, defined as the field required to generate an emission current of 1 nA, were approximately 1.66 and 1.38 V/µm, respectively. The turn-on field emission current saturated when the CNT length was about the same as the gate height.

Multi-wall carbon nanotube (CNT) films were fabricated by microwave plasma chemical vapor deposition at low temperatures (∼ 500 °C). The films when properly post-treated by laser irradiation exhibited a factor of 2–3 enhancement in the emission current, while the turn-on field ( E on ) was reduced from 4.89–5.22 to 2.88–3.15 V/μm. The introduction of excessive oxygen during laser irradiation, however, degrades the performance of field emission properties drastically. Raman spectroscopy measurements revealed the intimate correlation between the parameter I D / I G (intensity ratio between the two representative Raman peaks seen in carbon nanotubes) and the field emission performance. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses showed that the irradiation-induced modification of the tube morphology and crystallinity might be responsible for the observations.

In this paper, we have constructed and analyzed the field emission behavior of a single vertically aligned free standing carbon nanotube (CNT) with a gate electrode in order to verify the feasibility of using a single CNT as the low-voltage field emission electron source. The single vertically aligned CNT with gate electrode was fabricated by combining optical lithography, electron beam lithography (EBL) and inductively coupled plasma chemical vapor deposition (ICP-CVD) processes. A self-aligned process with a single mask was utilized to define the gated structure and the nano-size catalyst for CNT growth. A single vertically aligned CNT was then grown within the gate hole by ICP-CVD. The length-to-diameter ratio of CNT could be varied by adjusting the e-beam exposure time, and the CNT height was controlled to equal to the gate-to-cathode spacing (800) nm in one gated device and less than the spacing (530 nm) in another device. The field emission characteristics of the integrated gate electrode devices were then measured under a scanning electron microscopy (SEM) with a three-axis nano-positioning device. The turn-on field of the gated devices with 800 and 530 nm height CNT were 2.77 and 3.57 V/μm, respectively, with applying − 10 V gate voltage, and 0 V anode voltage.

In this study, we demonstrate that by embedding a plasmonic coupling metal layer beneath the active layer of an organic light-emitting diode, the resultant device is capable of inducing significant blue shifts in CIE color space coordinates of emitting light from the green emitting material without compromising the lifetime of the parent material. The implemented device consists of multilayers of organic emitting materials sandwiched by two thin metal layers to form a metal-dielectric-metal (MDM) cavity-like structure. The original green emission with CIE coordinates of (0.22, 0.56) was significantly color space blue-shifted to CIE coordinates of (0.10, 0.53). The MDM device exhibits an efficiency of 62 cd/A at a luminance of 1000 cd/m2, which represents a two-fold enhancement of current efficiency. Moreover, the spectral peak intensity is 4.3 times higher than that in a conventional device, which is much higher than that expected for an optical microcavity model, suggesting that the Purcell effect result...

This work reports the color-tunable mixed photoluminescence (PL) emission from an Alq3 organic layer in an Au-Alq3-Au plasmonic structure through the combination of organic fluorescence emission and another form of emission that is enabled by the surface plasmons in the plasmonic structure. The emission wavelength of the latter depends on the Alq3 thickness and can be tuned within the Alq3 fluorescent spectra. Therefore, a two-color broadband, color-tunable mixed PL structure was obtained. Obvious changes in the Commission Internationale d’Eclairage (CIE) coordinates and the corresponding emission colors of Au-Alq3-Au samples clearly varied with the Alq3 thickness (90, 130, and 156 nm).

The present study concerns with the secondary electron emission coefficient, γ, of the cathode materials used in the newly developed flat electron emission lamp (FEEL) devices, which essentially integrates the concept of using cathode for fluorescent lamp and anode for cathode ray tube (CRT) to obtain uniform planar lighting. Three different cathode materials, namely fluorine-doped tin oxide (FTO), aluminum oxide coated FTO (Al2O3/FTO) and magnesium oxide coated FTO (MgO/FTO) were prepared to investigate how the variations of γ and working gases influence the performance of FEEL devices, especially in lowering the breakdown voltage and pressure of the working gases. The results indicate that the MgO/FTO bilayer cathode exhibited a relatively larger effective secondary electron emission coefficient, resulting in significant reduction of breakdown voltage to about 3kV and allowing the device to be operated at the lower pressure to generate the higher lighting efficiency.

The gas discharge and photo-luminance properties of a planar lighting source featuring highly uniform light emission and mercury-free design were studied. The current density-voltage characteristics and the associated gas discharge of the devices operating with the values of the ratio of electric field to gas pressure (E/p) between 4.3 kV/Torr-cm and 35.7 kV/Torr-cm indicate that the width of the cathode fall extends over the entire gap between the two electrodes and the device is mostly in the obstructed discharge regime. The optical emission analysis confirmed the electron collision-induced gas emissions and strong effect of gas pressure on the phosphor emission when operated at constant current density, both are indicative of the primary roles played by the electron energy.

A high voltage full-bridge resonant inverter is proposed for driving carbon nanotube field emission lamp (CNTL). First, we construct an equivalent model of CNTL to exhibit its electric characteristics. Moreover, the high frequency sinusoidal driving strategy is employed to eliminate the arcing phenomenon caused by the traditional DC driving. And then the PLL feedback controller is used to stabilize the lamp luminance. Complete design considerations and mathematical model are detailed. All the experimental results agree with the theoretical predictions.

Plasma display panel is one of the most potential flat devices for large-size displays. Magnesium oxide thin films have been used as a protective layer to improve discharge characteristics and the lifetime of panel. So magnesium oxide thin film is worthy to be studied. Magnesium oxide thin films were prepared by e-beam gun evaporation at a substrate temperature of 200°C. Heat annealing treatment and ion assisted deposition effect on thin films were investigated. The relation between these characteristics of films has been studied. The characteristics of the deposited films, including optical properties, crystalline structure, and microstructure were discussed.

An electronic ballast, high reliability, stability and safety, must prepare the protection functions in order to avoid more critical hazards. In this paper, the high performance protections proposed mainly false ignition, open and short circuit protection actions have been completely designed and shown. Then, the protection circuit owns more benefits as small size, large cost saving and high efficiency. Moreover, this one can yet become a module structure as hybrid or integrated circuit. Now, the protection functions will be applied to and verified by the electronic ballast with the self-excited series resonant inverter system for fluorescent lamps.

In this study, a multi-color emission was observed from the large-area GaN-based photonic quasicrystal (PQC) nanopillar laser. The GaN PQC nanostructure was fabricated on an n-GaN layer by using nanoimprint lithographic technology. The regrown InGaN/GaN multiple quantum wells (MQWs) formed a nanopyramid structure on top of the PQC nanopillars. A lasing action was observed at ultraviolet wavelengths with a low threshold power density of 24 mJ/cm2, and a green color emission from InGaN/GaN MQWs was also achieved simultaneously.

We demonstrate a high-efficiency green organic light-emitting diode (OLED) with a solution-processed emissive layer composed of a novel green light emitting iridium complex, bis [5-methyl-8-trifluoromethyl-5H-benzo(c) (1,5)naphthyridin-6-one]iridium(pyrazinecarboxylate). By coupling with a proper host, the green device shows at 1000 cd m−2 an external quantum efficiency of 23.8%, current efficiency of 95.6 cd A−1, and efficacy of 60.8 lm W−1, the highest among all reported OLEDs with a solution-processed emissive layer. The high efficiency may be attributed to the host possessing a zero electron injection barrier, resulting in a more balanced carrier-injection.

We reveal in this communication a new finding regarding the use of a sky-blue emitter to generate purplish-blue emission from organic light emitting diodes (OLEDs) with a polarity matching and high-energy exciton generating host. The resulting device exhibits CIExy coordinates of (0.155, 0.063) and a 3.5% external quantum efficiency, with a 1.2 lm W−1 power efficiency at 100 cd m−2 as a sky-blue emitter, 1-((9,9-diethyl-9H-fluoren-2-yl)ethynyl)pyrene with CIExy of (0.190, 0.241) is doped into a host of 4,4′-bis(9-carbazolyl)-biphenyl, for example. The resulting purplish-blue emission enables a greater than 100% color saturation. The extraordinarily marked blue-shift may result from a low doping concentration to prevent bathochromic shift due to emitter segregation, a polarity matching host to further disperse the emitter, and an efficient host and guest energy level pairing that enables excitons to be generated on the host to trigger short wavelength emission. Furthermore, the host is capable of generating excitons with higher energy to facilitate the triggering of emission with a shorter wavelength. The high efficiency may be attributed to the low doping concentration preventing efficiency roll-off caused by concentration-quenching, the excitons generated on the host facilitating the occurrence of the effective host-to-guest energy transfer, and the employed host possessing an effective host-to-guest energy transfer effect. Notably, the new approach also works for other light-blue emitters in yielding a highly desirable deep-blue light, provided their molecular structure is free of steric hindrance.

We propose a lighting mechanism for generating uniform planar light. The device integrates electron beams induced by gas discharge with cathodoluminescence at the anode, where the spectra of the emitted light depend entirely on the phosphor materials coated on the anode. Consequently, ultraviolet is not required and the usage of mercury can be avoided. In addition, the features of double-side lighting, transparency, and gray-scale images indicate that the flat electron emission lamp might become potential candidate for the next generation green lighting source.

We describe a novel technique capable of controlling the oxygen content of YBa2Cu3O x (YBCO) films in a precise and reversible manner. The temperature dependence of resistivity and the distinct two-plateau behavior in critical temperature T co versus oxygen content plot of these films are consistent with those observed in the bulk and single crystals of YBCO. The O 1s and Cu 2p absorption spectra of these films were measured by polarization-dependent X-ray absorption spectroscopy (XAS). The intensity variations of the pre-edge peaks as a function of oxygen content are discussed. We also used these films to systematically study the electron-phonon coupling strength and the position of Fermi level by using a femtosecond pump-probe technique. A clear sign-reversal of the transient reflectivity, which was consistently explained by the thermomodulation model, was observed. Both of these optical measurements support the idea that the electronic structure of YBCO cuprates is based on the charge transfer model with hybridization between the Cu and O sites.