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Detailed characterization of color-by-blue EC emissive display. (a) Luminance-voltage characteristics of the blue and green/red phosphor layer-coated EC cells with SWPF and LWPF. The inset shows the color coordinates of the SWPF/LWPF-assisted RGB pixels compared with the CIE color coordinates and color gamut from the National Television Standard Committee (NTSC). (b) Switching time, TON and TOFF of the DEB-based EC cell with an active area of 0.25 cm 2 and a cell gap of 25 µm, as driven between ON and OFF states. The inset shows the continuous operation of the display module over 1000 cycles, suggesting the stable electrochromic performance of the EC cell. (c-d), Switching response as a function of cell structure parameters. The changes in TON and TOFF were measured for different cell gap thickness at a constant active area of 1.00 cm 2 in (c) and different active areas at a constant cell gap of 25 µm in (d).
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We report a novel full-color display based on the generation of full-color by blue light approach, so called color-by-blue display. This newly proposed color-by-blue light-valve display combines a blue backlight excitation source, a blue light-valve shutter, and front-emitting phosphor pixels. Careful evaluation shows that the detailed display char...
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... the ratio to 1.0, 10.9 and 2.1, demonstrating that the relative brightness ratio of the tri colors obtained from the SWPF/LWPF-assisted cell structure is comparable to those of commercialized CRTs or AMLCDs (Table 1). In fact, the measured values of the luminance from each of SWPF/LWPF-assisted RGB cells at 0 V were 310, 3380, and 650 cd/m 2 ( Fig. 5(a)), indicating that white luminance above 500 cd/m 2 can be easily obtainable from this emissive color-by-blue ...
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... (80 wt%) SWPF-only assisted (80 wt%) SWPF/LWPF assisted (G:50 wt%, R:60 wt%) The inset of Fig. 5(a) shows the CIE color coordinates of the SWPF/LWPF-assisted RGB EC cells compared with the CIE color coordinates from the National Television Standard Committee (NTSC). The CIE x,y color coordinates (0.15, 0.02) of the emission spectrum from the blue cell was deep enough to comply with the NTSC blue coordinates. The chromaticity ...
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... cycling durability and switching speed of the DEB-based EC cell were tested with 0.1 Hz square wave varying between 0 and 3 V. During the continuous operation over 1000 cycles, it did not show any significant drop in the emission intensity, as shown in the inset of Fig. 5(b). This reversible electrochromic performance of the EC cell observed here confirms the stable contemporary redox reaction of ferrocene in TBAP solution [10,19]. The small change in the reflectance, approximately less than 10% after 1000 cycles, results mostly from the improper sealing of the cell and the inadequate deaeration of the ...
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... small change in the reflectance, approximately less than 10% after 1000 cycles, results mostly from the improper sealing of the cell and the inadequate deaeration of the electrolyte. Figure 5(b) shows the detailed transmittance response of the DEB-based EC cell as driven between ON and OFF states. The rise time during the coloration process, T ON was defined as the time required for the reflectance to reach from 10% to 90% of its full reflectivity and the fall time, T OFF is determined from the time interval between from 90% to 10% of its full reflectivity during the bleaching process. ...
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... in most of organic-based EC devices, the switching time depends on the active area and the cell gap of the device, we varied the active area and the cell gap, and observed the changes in T ON and T OFF . Figure 5(c) shows the switching times, T ON and T OFF for the different cell gap thickness. When the cell gap thickness was varied with a constant active area of 1 x 1 cm 2 , T ON decreased almost linearly with the gap thickness, reaching a value of 212 ms for the gap thickness of 25 µm, while T OFF showed only very small variation between 265 ms and 367 ms. ...
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... improve the response of the coloration, the size of the cell gap demonstrated here has been limited to 25 µm only because of the saturated solubility of DEB in an NNP solution. Also, the switching characteristics of the DEB-based EC cells with various active areas ranging from 0.25 to 1.5 cm 2 were measured at a constant cell gap of 25 µm ( Fig. 5(d)). While the size of the active area did not make much difference for T ON , T OFF decreased from 430 ms to 87 ms with the active area. Fig. 6. Balance between RGB cells required for the correlated color temperature of 12000 K. The electroluminescence (EL) spectra of InGaN (blue), SrGa2S4:Eu (green) and CaAlSiN3:Eu (red) ...
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... This is the largest color reproduction area of real materials ever reported in any other kinds of PL materials which are applicable in color-by-blue display devices. 23,24 Nearly all values in Figure 3 and Table 1 indicate that the selected CGYOR-emitting PeQDs show adjustable peak wavelengths and color coordinates with excellent or proper PLQYs and narrow fwhm values for application in CGYORcolor converting monochromatic DC-LEDs, although further significant improvements in PLQY are necessary for the middle members of solid solution PeQDs between two end members of CsPbX 3 (X = Br, and I (or Cl)) PeQDs. ...
A narrow-emitting red, green and blue (RGB) perovskite quantum dot (PeQD)-based tri-colored display system can widen the color gamut over the National Television System Committee (NTSC) to 120%, but this value is misleading with regard to the color perception of cyan and yellow reproduced in the narrow RGB spectra. We propose that a PeQD-based six-color display system can reproduce true-to-life spectral distributions with high fidelity, widen the color gamut, and close the cyan and yellow gap in the RGB tri-colored display by adding cyan (Cy), yellowish green (Yg), and orange colors (Or). In this study, we demonstrated pure-colored CsPbX3 (X = Cl, Br, I, or their halide mixtures; Cl/Br and Br/I) PeQD-based monochromatic down-converted light-emitting diodes (DC-LED) for the first time, and incorporated PeQDs with UV-curable binders and long-wavelength-pass-dichroic-filters (LPDFs). CsPbX3 PeQD-based pure Cy-, G-, Yg-, Or-, R-emitting monochromatic DC-LED provide luminous efficacy (LE) values of 81, 184, 79, 80, and 35 lm/W, respectively, at 20 mA. We also confirmed the suitability and the possibility of access to future color-by-blue backlights for field-sequential-color liquid crystal displays, using six-color multi-package white LEDs, as well as future six-colored light-emitting devices with high vision and color performance. The fabricated six-color multi-package white LEDs exhibited an appropriate LE (62 lm/W at total 120 mA), excellent color qualities (color rendering index (CRI) = 96, special CRI for red (R9) = 97) at a correlated color temperature (CCT) of 6500 K, and a wide color gamut covering the NTSC up to 145% in the 1931 Commission International de l’Eclairage (CIE) color coordinates space.
... It concerns, particularly, display (Oh et al., 2011), photovoltaic cells for solar energy conversion (O'Reagan and Gra¨tzl, 1991) and electrochromic smart windows (ECWs) (Macedo et al., 1992). Although all these applications are important the ECWs technology attracts a particular attention because of its high potential for practical applications: for example, in security (conductor blindness by reflected light from rear car mirrors, aircrafts pilot protection against dazzling by the sun light, electrically controllable light attenuators, optical power limiting), and more particularly for energy conservation in buildings and a better inhouse comfort. ...
The paper presents the main results of our study on preparation and characterization of conducting biomembranes to be used as solid polymer electrolytes (SPEs). It bases on deoxyribonucleic acid (DNA), glycerol (GLY) and photosensitive chromophores, like Prussian Blue (PB). Its primary application is in fabrication of electrochromic windows. The new SPEs were characterized by UV-Vis and FTIR spectroscopy. They were used in preparation of small electrochromic devices (ECDs). The obtained devices were evaluated by cyclic voltammetry and also by spectroscopic methods. The results show their color change from blue pale to intense blue after application of a direct current (DC) electric field, making the composites very interesting for industrial applications in smart windows.
... Then, we characterized the crystal, morphological, and optical properties of the KSF red and SGS green phosphors [24][25][26][27][28]. Next, we introduced a novel strategy for fabricating freestanding remote-type films of phosphor/silicone binder hybrids that can be used as stacked GR films for the generation of white color. When the printing method was coupled with an interlayer and a floating/delamination technique, wafer-scale freestanding GR phosphor films were achievable [29][30][31]. Finally, we demonstrated several remote-type stacked GR films on a blue LED system that consisted of a narrowband red phosphor (KSF), a thiogallate green phosphor (SGS), and a blue LED to enhance the color gamut. ...
... In order to fabricate freestanding films, the optimum amount of the KSF (20 wt% -50 wt%) red and SGS (10 wt% -20 wt%) green phosphors were dispersed in a silicon binder (OE-6636A and OE-6636B, Dow Corning, Korea) separately to form the green and red phosphor pastes. Each paste was printed on a 150 μm spacer and then dried and hardened at 150 °C for 1 hour [29,30]. Next, the phosphor coated glass substrates were immersed in distilled water in order to separate the film from the substrate through dissolving the PEDOT/PSS. ...
In this study, we propose green/red bilayered freestanding phosphor film-capped white light-emitting diodes (W-LEDs) using InGaN blue LEDs and narrowband red and green phosphors to realize a wide color gamut in a liquid crystal display (LCD) backlight system. The narrowband K2SiF6:Mn⁴⁺ (KSF) red and SrGa2S4:Eu²⁺ (SGS) green phosphors are synthesized using a facile etching synthetic process and flux-aided solid state reaction under a H2S atmosphere, respectively, and the freestanding phosphor films are fabricated using a delamination method with water-soluble polymer, polystyrene sulfonic acid, PEDOT/PSS, and interlayered phosphor film. Various phosphor concentrations of green/red bilayered freestanding phosphor film-capped W-LEDs exhibit a correlated color temperature (CCT) and luminous efficacy range of 11,390 K ~6,540 K and 99 lm/W ~124 lm/W, respectively, with an applied current of 60 mA. The W-LED with green (12.5 wt%)/red (40 wt%) bilayered phosphor film, which exhibited luminous efficacy of 105 lm/W at the CCT of 8,330 K, is selected and the color gamut of the bare LED and phosphor RG and the filtered RGB triangle is calculated to be more than ~95% and ~86.4%, respectively, relative to the NTSC in the 1931 CIE color coordinates space.
... For maximized forward emission efficiency and improved green and red subpixel color, a shortwave pass dichroic filter (SPDF) was coated on the rear side of the green and red colorconversion layers to reflect the backward emission of the phosphor layers, and a long-wave pass dichroic filter (LPDF) was coated on the front side of the green and red color-conversion layers to reflect and recycle the otherwise transmitted blue light passing through green/red phosphor layers. Recently, both highly efficient SPDF and LPDFs were developed by our group to enhance the forward efficiency of yellow emission from YAG:Ce phosphor-on-cup blue LEDs and to fabricate monochromatic LEDs by reflecting transmitted blue light from the phosphor layers, respectively [9][10][11][12]. The same concept of blue-passing and green/red-reflecting SPDFs with green/red-passing and blue-reflecting LPDFs was employed in colorby-blue QD-LED to enable the recycling of backward emitted green/red light and the removing of unwanted blue light from the green/red phosphor layer, as shown in Fig. 1. ...
... Finally, Al cathode was thermally evaporated on top of the ETL. Figure 2(a) shows the schematic diagrams of the basic structure of the color-by-blue QD-LED. [9][10][11][12]: Dielectric LPDFs and SPDFs were fabricated on glass substrates. For the fabrication of the stacks, terminal eighth-wave-thick TiO 2 (25 nm) and quarter-wave-thick SiO 2 (73 nm) nano-multilayered films ((0.5TiO 2 /SiO 2 /0.5TiO 2 ) 9 , LPDF) and terminal eighth-wave-thick SiO 2 (59 nm) and quarter-wave-thick TiO 2 (77 nm) nano-multilayered films ((0.5SiO 2 /TiO 2 /0.5SiO 2 ) 9 , SPDF) were coated onto glass substrates by e-beam evaporation at 250°C. ...
... KER-2500A, KER-2500B) to form the green and red phosphor pastes. Each paste was printed on a glass and SPDF with a 200 μm spacer and then, dried and hardened at 150°C for 1 hour [12]. Figure 2(c) shows the normalized EL spectrum of a blue-emitting CdZnS/ZnS QD-LED and normalized PL spectra of green and red phosphor films. ...
We report a novel full-color display based on the generation of full-color by a highly efficient blue QD-LED light approach, or so called color-by-blue QD-LED display. This newly proposed color-by-blue QD-LED display combines a blue CdZnS/ZnS QD-LED blue subpixel and excitation source with front-emitting green/red phosphor subpixels. It is carefully estimated that the detailed display characteristics as well as full color-conversion and reasonable device efficiency of blue, green, and red satisfy the minimum requirements for display application. Also, we would like to emphasize that the proposed blue, green, and red device shows maximum luminance of 1570, 12920, and 3120 cd/m², respectively, luminous efficiency of 1.5, 12.1, and 2.5 cd/A, respectively, and external quantum efficiency of 6.8, 2.8, and 2.0%, respectively. It is expected that full color generation by color-by-blue QD-LED will lead to further technological advancements in the area of efficient and facile display applications.
... In this study, two types of LPDFs with nine periods of 0.5TiO 2 /SiO 2 /0.5TiO 2 multilayers (L515 and L535; 515 and 535 nm at the half-band-edge wavelength, respectively) and two types of SPDFs with nine periods of 0.5SiO 2 /TiO 2 /0.5SiO 2 multilayers (S550 and S580; 550 and 580 nm at the half-band-edge wavelength, respectively) were fabricated as capping filters for the production of green monochromatic pc-LEDs. Table 1 shows the thickness of each dielectric layer of the LPDFs and SPDFs, and Fig. 4 shows the transmittance spectra and photographs of the two types of LPDFs and SPDFs [11,12,15,16]. Fabrication of BPFs: The BPFs were designed by combining both LPDFs and SPDFs [17]. ...
... In order to address this problem, we adopt the 2D polystyrene (PS) monolayer as a scattering layer by scooping a PS monolayer from the water surface to the top of the BPF substrate (see Fig. 11(c)). PS microbeads (2-μm diameter) are considered to be a good light-scattering layer, because this size shows a large light-scattering coefficient when calculated from Mie scattering theory [15,16]. Thus, the angular dependence of the optical properties is reduced by coating a 2D PS scattering layer on top of the BPF-capped green pc-LEDs. ...
This study introduces a “greener” green monochromatic phosphor-converted light-emitting diode (pc-LED) using a band-pass filter (BPF) combined with a long-pass dichroic filter (LPDF) and a short-pass dichroic filter (SPDF) to improve the color quality of our previously developed LPDF-capped green pc-LED. This can also address the drawbacks of III-V semiconductor-type green LEDs, which show a low luminous efficacy and a poor current dependence of the efficacy and color coordinates compared to blue semiconductor-type LEDs. The optical properties of green monochromatic pc-LEDs using a BPF are compared with those of LPDF-capped green pc-LEDs, which have a broad band spectrum, and III-V semiconductor-type green LEDs by changing the transmittance wavelength range of the BPF and the peak wavelength of the green phosphors. BPF-capped green monochromatic pc-LEDs provide a high luminous efficacy (134 lm/W at 60 mA), and “greener” 1931 Commission Internationale d'Eclairage (CIE; CIEx, CIEy) color coordinates (0.24, 0.66) owing to the narrowed emission spectrum. We also propose a two-dimensional (2D) polystyrene (PS) microbead (2-μm diameter) monolayer as a scattering layer to overcome the poor angular dependence of the color coordinates of the transmitted light through a nano-multilayered dichroic filter such as an LPDF or BPF. The 2D PS scattering layer improves the angular dependence of the green color emitted from a BPF-capped green pc-LED with only 3% loss of luminous efficacy.
Quantum dots (QDs) are used in displays as they have several advantages including high illumination efficiency and color rendering, low cost, and mass production capacity. The excellent luminescence and transport charging properties of QDs have resulted in their use in QD-based light emitting diodes (LEDs), which have gained significant interest in display and solid-state lighting applications. In this article, we discuss the fabrication of full-color μLED devices using QDs by techniques such as inkjet printing and quantum dots photoresist (QDPR). Fabrication with the photoresist matrices reduces the crosstalk effect and optimizes the optical efficiency. Alternatively, nanoring structures and inkjet printing can be combined to achieve full-color monolithic LEDs. Additionally, the QDPR method can be easily scaled up as it is compatible with traditional photolithography and deposition of different thicknesses of QDPR on semipolar μLED can achieve wavelength stability. Finally, the enhanced full-color applications of highly effective QD μLEDs are presented.
The development of highly efficient and stable red (R) CsPb(Br0.35I0.65)3/CsPb2Br5 and green (G) CsPbBr3/CsPb2Br5 core/shell perovskite quantum dots (PeQDs) can facilitate the realization of highly efficient and wide-color-gamut, PeQD-emissive liquid crystal displays (LCDs). The photoluminescence quantum yields (PLQYs) for red and green (RG) core/shell PeQDs reached ~77.4% and ~78.9%, respectively. The enhanced photo-stability, water-resistant, and thermal stability of the RG core/shell PeQD film implies more opportunities to fabricate RG color- converting films with it to replace color filters (CFs) in conventional LCDs. The realization of color-by-blue PeQD-emissive LCDs can overcome technical challenges related to conventional CF-assisted LCDs, such as improved device efficiency and an enlarged color gamut. The relative conversion efficiency and color gamut of a color-by-blue PeQD-emissive LCD consisting of RG PeQD films sandwiched in the form of a RG-recycling bottom layer and a blue-filtering top dichroic filter are 1.94 times higher and 1.74 times wider than those of a conventional CF-LCD with a 2-phosphor-converted white-light-emitting diode (2pc-WLED). Therefore, the overall enhanced efficiency of PeQD-emissive LCDs was determined to be 4.28 times higher than that of a conventional 2pc-WLED-based CF-LCD. This color-by-blue core/shell PeQD-emissive LCD provides an excellent opportunity for the creation of new types of highly efficient LCDs.
Color-by-blue quantum dot (QD)-emissive liquid-crystal displays (LCDs) with eco-friendly, green, red (GR) InP/ZnSeS/ZnS QD films are introduced to overcome the disadvantages of conventional color-by-white color filter (CF)-assisted LCDs, such as a narrow viewing angle, low external device efficiency of these types of LCDs, and a restricted color gamut. In this study, the color-by-blue InP-based QD-emissive LCD consists of a blue (B) light-emitting diode (LED) and GR InP-based QD films sandwiched between a light recycling filter and a long-wavelength pass dichroic filter. The GR InP-based QDs are synthesized with a high photoluminescence quantum yield (>77%) and narrow bandwidth (<40 nm), which are suitable for display applications. The overall enhancement of InP-based QD-emissive LCDs, in this case by the enhanced efficiency of a blue LED backlight transmitted through the LC shutter compared to a white LED backlight and the improved efficiency of the enlarged color gamut, is 2.42 times that of a conventional red, green, and blue (RGB) CF-LCD with a GR phosphor-converted (pc)-LED (a B LED + R K2SiF6:Mn + G β-SiAlON:Eu phosphor) backlight. Therefore, this considerable enhancement of the external efficiency of a QD-emissive LCD makes it more feasible as a replacement for conventional RGB CF-assisted LCDs.
Electrospinning process of samarium-complexes doped PMMAs is carried out to fabricate ultrafine fibers with uniform diameter of about 230nm. Under ultraviolet excitation, luminescence comparison between bulks and nanofibers verifies the existence of spectral reshaping, which alters emission ratio of ligands to Sm3+, and the effectiveness of electrospun fibrosis in enhancing fluorescence emission is further identified in the case of Phen containing. Meanwhile, color tunability achieves with fluorescence color changing from reddish-orange in bulks to near-white light in nanofibers. The nanosizing in rare-earth phosphors by electrospun fibrosis is proved to optimize the fluorescence properties, which provide a new route to develop the effective light-converting materials.
