Emissive Mode Research Articles

Reflective and Emissive Dual Mode Display Cell with Electrochromism and Electrochemiluminescence

We are studying novel dual-mode display (DMD) driven by electrochemical reaction. Our DMD cell shows electrochromic (EC) properties as reflective mode and electrochemiluminescent (ECL) properties as emissive mode. In this paper, we reported the effect of structure and materials on characteristics of reflectiveemissive dual-mode display cell.

Electroswitching of Emission and Coloration with Quick Response and High Reversibility in an Electrochemical Cell

No fade to grey: Electroswitching of emission and coloration was achieved for a combination of a luminescent Eu(III) complex and an electrochromic molecule of diheptyl viologen (HV(2+)), indicating that such a combination could be used as a display material with dual emissive and reflective modes. The Prussian blue (PB)-modified electrode improved the response time and reversibility for the switching of emission and coloration, by acting as a counter electrode for the electrochromism of HV(2+).

66.4: High Contrast Edgelit Frontlight Solution for Reflective Displays

AbstractWe developed an LED edgelit frontlight with a large view cone, high contrast in both emissive and reflective modes, and compatibility with fully laminated module architectures. A high volume manufacturing ready glass‐based frontlight lightguide technology is introduced, which includes unidirectionally reflective light turning microstructures having high reflectivity towards the display and low reflectivity towards the viewer.

Establishing Dual Electrogenerated Chemiluminescence and Multicolor Electrochromism in Functional Ionic Transition-Metal Complexes

A combination of electrochromism and electroluminescence in functional materials could lead to single-layer dual electrochromic/electroluminescent (EC/EL) display devices, capable of simultaneous operation in emissive and reflective modes. Whereas such next generation displays could provide optimal visibility in any ambient lighting situation, materials available that exhibit such characteristics in the active layer are limited due to the required intrinsic multifunctionality (i.e., redox activity, electroluminescence, electrochromism, and ion conductivity) and to date can only be achieved via the rational design of ionic transition-metal complexes. Reported herein is the synthesis and characterization of a new family of acrylate-containing ruthenium (tris)bipyridine-based coordination complexes with multifunctional characteristics. Potential use of the presented compounds in EC/EL devices is established, as they are applied as cross-linked electrochromic films and electrochemiluminescent layers in light-emitting electrochemical cell devices. Electrochromic switching of the polymeric networks between yellow, orange, green, brown and transmissive states is demonstrated, and electrochemiluminescent devices based on the complexes synthesized show red-orange to deep red emission with λ(max) ranging from 680 to 722 nm and luminance up to 135 cd/m(2). Additionally, a dual EC/EL device prototype is presented where light emission and multicolor electrochromism occur from the same pixel comprised of a single active layer, demonstrating a true combination of these properties in ionic transition-metal complexes.

Novel Display Device with Dual Emissive and Reflective Modes by Using Luminescent Lanthanide (III) Complexes and Electrochromic Materials

Novel Display Device with Dual Emissive and Reflective Modes by Using Luminescent Lanthanide (III) Complexes and Electrochromic Materials

Improvement in reflective–emissive dual-mode properties of electrochemical displays by electrode modification

We studied the electrochromic (EC) and electrochemiluminescent (ECL) properties of a novel dual-mode display (DMD) cell that was enabled for reflective and emissive modes of representation by introducing both EC and ECL materials into an electrochemical cell. We fabricated EC, ECL, and DMD cells based on a simple-mixture solution or modified electrodes and compared their properties to clarify the advantage of a DMD system based on modified electrodes. Both the solution- and modified electrode-based DMDs showed EC properties in the reflective mode under dc bias application and ECL properties in the emissive mode under ac bias application. Although the solution-based DMD cell featured a very simple structure, some improvements related to side reaction and quenching reaction were required. The modified electrode-based DMD cell was fabricated to improve these aspects. The advantage of the DMD model based on the modified electrodes was certainly suggested by comparisons of the results with those of EC, ECL, and DMD cells based on a simple-mixture solution.

Fabrication of Novel Reflective–Emissive Dual-mode Display Cell Based on Electrochemical Reaction

Abstract We successfully demonstrated a novel reflective–emissive dual-mode display (DMD) cell with electrochromic and electrochemiluminescence reactions. This DMD cell has simple structure and allows the selection of reflective or emissive mode by selecting DC or AC driving, respectively.

Investigation of magnetically self-insulated effect in an ion diode with an explosive emission potential electrode

The results of an experimental investigation of a magnetically self-insulated effect in an ion diode in bipolar-pulse mode are presented. The investigations were accomplished at the TEMP-4M accelerator by formation of a first negative pulse (100 ns, 150–200 kV) and a second positive pulse (80 ns, 200–300 kV) [G. E. Remnev et al., Surf. Coat. Technol. 114, 206 (1999)]. Plasma behavior in the anode-cathode gap was analyzed according to the current-voltage characteristics of the diode with a time resolution of 0.5 ns. It is shown that during the discrete emissive surface mode, the magnetic field influence on plasma dynamics is slight. During the space charge limitation mode, the current-voltage characteristics of the diode are well-described by the Child–Langmuir ratio. The drift speed of electrons in the diode exceeds 80 mm/ns and the effect of magnetic insulation is insignificant. It was discovered, when plasma formation at the potential electrode is complete and up until the second positive pulse that the plasma speed is constant and equals to 1.3±0.2 cm/μs. After the voltage polarity at the potential electrode changes (second pulse), plasma breakup at the anode-cathode gap takes place. The impedance of the diode begins to increase and, when the total current is more than 30 kA, the diode impedance exceeds the calculated values by more than three times. The energy efficiency and limiting characteristics of the magnetically self-insulated diode are determined.

Cathodoluminescence study of semiconductor oxide micro‐ and nanostructures grown by vapor deposition

Nano- and microstructures of SnO(2), In(2)O(3) and ZnO have been grown during thermal treatment of compacted powders under argon flow. Indium-doped SnO(2) tube-shaped structures with rectangular cross-section are obtained by adding a fraction of In(2)O(3) to the starting SnO(2) powder. In-rich nanoislands were found to grow on some edges of the tubes. ZnO nanostructures doped with Sn or Eu were grown by adding SnO(2) and Eu(2)O(3) powder, respectively, to the ZnO precursor powder. All the samples have been characterized by the emissive and cathodoluminescence (CL) modes of scanning electron microscopy. CL images from SnO(2):In and In(2)O(3):Sn tubes and islands show a higher emission from the Sn-rich structures related to oxygen deficiency. CL of doped ZnO enables to detect the presence of dopant in specific regions or structures. CL appears to be a useful technique to study optical and electronic properties of semiconductor oxide nanostructures.

67.3: Electrochemical Reaction Display with Dual Reflective and Emissive Modes

AbstractWe have developed an electrochemical reaction display (ECRD) that can be operated in dual reflective and emissive modes in an entire pixel area of a single device. The ECRD utilizes electrochromic (EC) and electrogenerated chemiluminescence (ECL) reactions. These two electrochemical reactions can be controlled independently by adding a luminescent molecule to a liquid electrolyte of an EC cell with three electrodes. In the reflective mode, the ECRD cell exhibits high reflectance (47%) and high contrast ratio (6:1). In the emissive mode, the cell can show luminescent moving images because of the fast response time (10 ms).

Theory of subwavelength hole arrays coupled with photonic crystals for extraordinary thermal emission

A subwavelength array of holes in a metal film residing on a silicon photonic crystal exhibits very sharp resonant absorption modes and extraordinary thermal emission. We developed a rigorous electromagnetic theory of subwavelength emitters based on the scattering matrix approach. Simulations exhibit a resonant absorption and emission when the photonic crystal is present, in good agreement with measurements. Diffraction resonances are found within the silicon photonic crystal. These combine with the extraordinary transmission through subwavelength hole arrays to generate resonant absorption in subwavelength arrays of metallodielectric photonic crystals. There is enormous enhancement of fields within the holes for resonant emissive modes.

Tunability of resonant wavelength by Fabry–Perot microcavity in organic light-emitting diodes

Distributed Bragg reflectors (DBR) with different reflection wavelengths were designed, and were used to fabricate microcavity organic light-emitting diodes (OLEDs) based on tris(8-hydroxyquinoline)-aluminum (Alq 3) as the emitter and N, N′-di(naphthalene-1-yl)- N, N′-diphenyl-benzidine (NPB) as the hole-transporting layer. The microcavity was composed of DBR dielectric mirror and metal electrode aluminum (Al) mirror. Some effects of vertical optical Fabry–Perot microcavity on spontaneous emission in OLEDs were investigated. Spectral narrowing, enhancement of emitting intensity and anglular dependence of emission were observed due to the microcavity effect. It was found experimentally that the utilization of DBR is a better method to adjust the emissive mode in the resonant cavity in OLEDs well. Thus the realization of different color light emission becomes possible by the combination of carefully designed microcavity and electroluminescent organic semiconductors in a single LED.

Display device with dual emissive and reflective modes

A display device with dual electroluminescence and electrochromic display functions is described. The device consists of two layers of polymeric thin films, one of which is an electrochromic polymer and the other an electroluminescence polymer, that are sandwiched between two electrodes. Both polymers are blended with a solid electrolyte. The device functions as an electroluminescence device when positively biased, and as an electrochromic device if biased negatively instead. The measured current density for the electrochromic mode of operation was found to be two orders of magnitude lower than that for the electroluminescence mode. This functional duality demonstrates the successful combination of the option of light-emitting display and the power saving electrochromic mode for portable devices.

Effect of laser irradiation on the luminescence of Mg and Si-doped GaN films

Pulsed laser treatments have been performed in GaN samples of both n- and p-type conductivity. The laser induced changes have been monitored by emissive mode and cathodoluminescence (CL) in a scanning electron microscope. Emissive mode observations indicate a moderate laser induced recrystallization. The luminescent emission has been characterized in both types of samples, GaN:Si and GaN:Mg. Whereas the evolution of CL in the Si doped samples could be explained by the occurrence of laser induced annealing, the luminescent behavior of the Mg doped samples upon irradiation seems to be more complex and a strong relation with the compensation or Mg activation is suggested. Several luminescence bands with maxima ranging from 3.3 to 2.7 eV and their dependence on irradiation conditions have been studied.

Correlation between crystal structure, quality and luminescence in torch flame grown diamond films

Flame grown diamond films on a molibdenium substrate are characterised by cathodoluminescence (CL), photoluminescence (PL), micro-Raman and scanning electron microscopy in the emissive mode. Different crystal habit regions grow with an annular symmetry. A correlation between morphology, CL, PL and Raman measurements is obtained for each region. The influence of the growth parameters is discussed.

Impurity phase recognition in YBCO high T c superconductors by cathodoluminescence spectroscopy

Cathodoluminescence (CL) microscopy of YBa2Cu3O7−x using scanning electron microscopy (SEM) and light microscopy revealed the presence of impurity grains with a strong CL contrast. The impurities, present within internal pores of the material, were characterized by wavelength-resolved CL spectroscopy and by energy dispersive X-ray (EDX) analysis. Consideration of electron-beam conditions in the SEM resulted in a full correlation of microstructural features between the CL and electron emissive modes. Yellow CL emissions were generated from yttria-rich phases, and blue emissions were generated from copper-richbarium-cuprate phases. EDX also demonstrated the presence of silicon within the pores. It is suggested that a glassy silicate phase is present, which may wet the impurity-phase grains. In identifying and characterizing these impurities, the CL technique proved to be a powerful tool in the determination of the quality of the pellet sample and hence its suitability as a target material for the laser-ablation deposition of thin films.

Time-resolved electron spin resonance spectra of linked radical pairs on laser excitation of zinc tetraphenylporphyrin-viologen systems

Photoinduced electron transfer from the zinc tetraphenylporphyrin moiety to the viologen unit in linked compounds in reversed micelles generated radical pairs, which afforded chemically induced dynamic electron polarization (CIDEP) spectra at room temperature. The CIDEP spectra varied with the number of methylene groups (n) in the alkyl spacer of the linked compounds. In the case of longer spacers (n = 6 and 8), common E/A/E/A patterns were observed throughout the measurement (0.7-5 [mu]s). The signal pattern could be simulated by a formula for the well-known spin-correlated radical pair mechanism, and the corresponding exchange coupling (J) was evaluated ([minus]0.4 mT). In the case of ZP4V, the CIDEP signals rapidly changed with elapsed time (0.5-3 [mu]s) from the absorptive to emissive mode. The observation was explained on the basis of a strong contribution of the triplet mechanism in the photogeneration of the radical pair in the early period of measurement. 15 refs., 2 figs.

QUANTITATIVE SCANNING ELECTRON MICROSCOPY OF SURFACES

The emissive modes of secondary and backscattered electrons in a scanning electron microscope work more quantitavely for material and topographic contrasts and can better separate different types of contrast when using a multi-detector system.

An electron spin resonance and time-resolved CIDEP study of the oxidation of ascorbic acid by pyruvic acid, duroquinone, and vitamin K1

The photooxidation of vitamin C by pyruvic acid and its derivatives, duroquinone, and vitamin K1, is systematically studied by the combined esr and time-resolved CIDEP technique. Because of the unique property of the triplet pyruvic acid which is different from that of the duroquinone triplet, the choice of these model systems allowed the CIDEP observations of the initial polarization of the ascorbate radical anion and its counter primary radical in either the enhanced absorptive or the emissive mode. The results demonstrate the efficient photooxidation of vitamin C by the triplet vitamin K1 and that the latter triplet possesses similar properties as the triplet quinones. In the photooxidation system involving vitamin C and pyruvic acid, the adjustment of the pH of the aqueous solution afforded an opportunity to observe the photochemical reaction between two anions, the pyruvate anion and the ascorbate anion. Arguments were made in favor of an electron transfer mechanism for the oxidation of vitamin C by triplet vitamin K1 but against the electron transfer mechanism for the oxidation of vitamin C by triplet pyruvate anion. T1 values of the primary radicals estimated from their CIDEP transient responses at low microwave power are reported and it was suggested that the hydrogen-bonding capacity of the ascorbate radical anion in water does not contribute significantly to the relative difference of T1's between itself and the counter pyruvic ketyl radical.

A cathodoluminescent study of quartz sand grains

SUMMARYSurfaces and cross sections of individual quartz sand grains have been examined in both the emissive and cathodoluminescent (CL) modes using a scanning electron microscope. The cathodoluminescent micrographs reveal sub‐surface information not seen in the emissive mode micrographs. The CL features are generally associated with previous stressing, fracturing or abrasion of the grains, and are probably related to the formation of disrupted‐lattice and/or amorphous quartz. The sequence of events during the formation of these features can be identified on many grains by studying the spatial distribution of the most common form of CL contrast—narrow dark bands. On other grains, irregularly distributed dark patches are generally observed to be a surface phenomenon, but the distribution, depth and intensity of these features can be studied by examining cross sections of grains. While it is common for the banded features to cross the entire specimen, it is rare for the diffuse areas to penetrate more than 30 μm. Some grains when experimentally heated above the α‐β transition temperature show a marked change and even a complete reversal in CL contrast.Such studies of grains in cathodoluminescence can supplement the environmental information obtained from emissive mode micrographs of geological materials.