This study explores the realization of high-efficiency white LED lighting by applying cyan-emitting quantum dot (CQD) and red-emitting quantum dot (R-QD) deposition without any host matrix onto a yellow-emitting phosphor-in-glass (YPIG) substrate using an aerosol-assisted deposition (AAD) process. The AAD process facilitates the direct formation of densely packed QD-deposited layers on the substrate, effectively addressing challenges such as optical efficiency loss and degradation typically associated with organic host matrices. C-QD and R-QD coatings, deposited with thicknesses of 0.84 μm and 0.77 μm on the upper and lower Y-PIG substrate, exhibited robust color conversion properties. These films achieved a luminous efficacy of 77 lm/W and a high color rendering index (CRI) of 96.8 under blue light excitation. The dual-layer structure produced highquality light closely resembling natural daylight, as confirmed through real image. Consequently, the research suggests the potential of AAD-based QD deposition to achieve superior performance without relying on host matrices, offering a viable solution for high-efficiency lighting applications. Further optimization of deposition parameters and exploration of diverse substrates and QD material combinations are expected to expand the applicability of this technique in future research.

We studied white organic light-emitting diodes using blue fluorescent and red phosphorescent materials.White single OLEDs were fabricated using SH-1 : BD-2 (3 vol.%) and CBP : Ir(mphmq)2(acac) (2 vol.%) as emitting layer (EML). The white single OLED using SH-1 : BD-2 (3 vol.% 8 nm) / CBP : Ir(mphmq)2(acac) (2vol.% 22 nm) as emitting layer showed maximum current efficiency of 8.8 cd/A, Commission Internationale del``Eclairage (CIE) coordinates of (0.403, 0.351) at 1,000 cd/㎡, and variation of CIE coordinates with (0.402 ±0.012, 0.35 ± 0.002) from 500 to 3,000 cd/㎡. The white tandem OLED using SH-1 : BD-2 (3 vol.% 12 nm) /CBP : Ir(mphmq)2(acac) (2 vol.% 18 nm) showed maximum efficiency of 19.6 cd/A, CIE coordinates of (0.354,0.365) at 1,000 cd/㎡, and variation of CIE coordinates with (0.356 ± 0.016, 0.364 ± 0.002) from 500 to 3,000 cd/㎡. Maximum current efficiency of the white tandem OLED was more twice as high as the single OLED. Our findings suggest that tandem OLED was possible to produce improved efficiency and excellent color stability.

We studied optical and electrical properties of two-wavelength white tandem organic light-emitting diodes using red and blue materials. White fluorescent OLEDs were fabricated using Alq3 : Rubrene (3 vol.% 5 nm) / SH-1 : BD-2 (3 vol.% 25 nm) as emitting layer (EML). White single fluorescent OLED showed maximum current efficiency of 9.7 cd/A, and tandem fluorescent OLED showed 18.2 cd/A. Commission Internationale de l``Eclairage (CIE) coordinates of single and tandem fluorescent OLEDs was (0.385, 0.435), (0.442, 0.473) at 1,000 cd/㎡, respectively. White hybrid OLEDs were fabricated using SH-1 : BD-2 (3 vol.% 10 nm) / CBP : Ir(mphmq)2(acac) (2 vol.% 20 nm) as EML. White single hybrid OLED showed maximum current efficiency of 7.8 cd/A, and tandem hybrid OLED showed 26.4 cd/A. Maximum current efficiency of tandem hybrid OLED was more twice as high as single OLED. CIE coordinates of single hybrid OLED was (0.315, 0.333), and tandem hybrid OLED was (0.448, 0.363) at 1,000 cd/㎡. CIE coordinates in white tandem OLEDs compared to those for single OLEDs observed red shift. This work reveals that stacked white OLED showed current efficiency improvement and red shifted emission than single OLED.

Novel materials of Zn(HPB)2 and Ir-complexes were respectively synthesized as blue or redemitting material. White Organic Light Emitting Diodes (OLED) were fabricated by using Zn(HPB)2 for ablue emitting layer, Ir-complexes for a red emitting layer and Alq3 for a green emitting layer. White OLED was fabricated by using double emitting layers of Zn(HPB)2 and Alq3:Ir-complexes, and hole blocking layer of BCP. We also varied the thickness of BCP. When the thickness of BCP layer was 5nm, white emission was achieved. We obtained a maximum luminance of 3,500 cd/m2. The CIE coordinates was (0.375, 0.331). From this study, we could propose that the hybrid structure is efficient in lighting application of white OLED by improvement of color purity.

We synthesized new materials of Zn(HPB)2 and Ir-complexes as blue or red emitting material. We fabricated white Organic Light Emitting Diodes (OLED) by using Zn(HPB)2 for the blue emitting layer, Ir-complexes for the red emitting layer and Alq3 for the green emitting layer. We fabricated white OLED by using double emitting layers of Zn(HPB)2:Ir-complexes and Alq3. The doping rate of Ir-complexes was varied, such as 0.2%, 0.4%, 0.6%, and 0.8%, respectively. When the doping rate of Zn(HPB)2:Ir-complexes was 0.6%, white emission was achieved. The Commission Internationale de l`Eclairage (CIE) coordinates of the white emission was (0.322, 0.312).

Five factors are identified, which affect the performance of optical filter: 1) type of opticalglass, 2) existence of Fe, 3) photo pic coating type, 4) coating form, and 5) coating thickness. If weconsider all the levels of five factors, there are 360 possible candidates. We determined five evaluationcriteria, which can be used to evaluate possible candidates. For the performance measures we selectedwhite-state avearge voltage, black-state average voltage, and black-state error rate. And we addedeconomic criterion and quality and maintenance criterion. Through the two-step statistical analysis ofwhite-state avearge voltage, black-state average voltage, and black-state error rates, we selected finalfour candidates. Based on the five criteria we finally determined optimal optical filter using AHP.

The object of this paper is to develop optimal optical filter, which can be used to identify thefinancial account and read the information. The five factors which affect the performance of the opticalfilter are identified as optical glass type, existence of Fe, Photo pic coating type, and coating form. Inthis study we seek to determine the optimal combination for the best design of the optical filter. For eachcombination, the performances of optical filter are investigated using the proper experimental equipmentsand methods. White-state voltage, black-state voltage, and black-state error rate are used for theperformance measures. Through the statistical analysis of the performance data collected, we havedetermined the optimal design of the optical filter.

We have fabricated white organic light-emitting diodes (OLEDs) by co-doping of red and blue phosphorescent guest emitters into the single host layer. Tris(2-phenyl-1-quinoline) iridium(III) [Ir(phq)3]and iridium(III)bis[(4,6-di-fluorophenyl)-pyridinato-N,C2`]picolinate (FIrpic) were used as red and blue dopants, respectively. The effects of dopant concentration on the emission, carrier conduction and external quantum efficiency characteristics of the devices were investigated. The emissions on the guest emitters were attributed to the energy transfer to the guest emitters and direct excitation by trapping of the carriers on the guest molecules. The white OLED with 5% FIrpic and 2% Ir(phq)3 exhibited a maximum external quantum efficiency of 19.9% and a maximum current efficiency of 45.2 cd/A.

We have fabricated white organic light-emitting diodes (OLEDs) using several thicknesses ofelectron-transport layer. The multi-emission layer structure doped with red and blue phosphorescent guestemitters was used for achieving white emission. 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) wasused as an electron-transport layer. The thickness of BCP layer was varied to be 20, 55, and 120 nm. The current efficiency, emission and recombination characteristics of multi-layer white OLEDs wereinvestigated. The BCP layer thickness variation results in the shift of emission spectrum due to therecombination zone shift. As the BCP layer thickness increases, the recombination zone shifts toward theelectron-transport layer/emission-layer interface. The white OLED with a 55 nm thick BCP layerexhibited a maximum current efficiency of 40.9 cd/A.

Recently, remote phosphor is reported for white LED enhancing of phosphor efficiency compared with conventional phosphor-based W-LED. In this study, Remote phosphor was produced by screen printing coating on glass substrate with phosphor contents rated paste and heat treatment. The paste consists of phosphor, lowest softening glass frit and organic binders. Remote phosphor can be well controlled by varying the phosphor content rated paste. After mounting remote phosphor on top of blue LED chip, CCT, CRI, and luminance efficiency were measured. The measurement results showed that CCT, CRI. and luminance efficiency were 6,645, 68, and 1,161 n/W in phosphor 80 wt.% remote phosphor sintered at 600℃.

To study emission properties of white phosphorescent organic light emitting devices (PHOLEDs), we fabricated white PHOLEDs of ITO (150 nm) / NPB(30 nm) / TcTa(10 nm) / mCP(7.5 nm) / light-emitting layer(25 nm) / UGH3(5 nm) / Bphen(50 nm) / LiF(0.5nm) / Al(200 NM) structure. The total thickness of light-emitting layer with co-doping and blue-doping/ co-doping using a host-dopant system was 25 nm and the dopant of blue and red was FIrpic and Bt2Ir(acac) in UGH3 as host. respectively. The OLED characteristics were changed with position and thickness of doping layer and co-doping layer as light-emitting layer and the best performance seemed in structure of blue-doping(5 nm)/co-doping(20 nm) later. The white PHOLEDs showed the maximum current density of 34.5 mA /cm², maximum brightness of 5,731 cd/ m², maximum current efficiency of 34.8 cd/A, maximum power efficiency of 21.6lm/w, maximum quantum effiency of 15.6%, and a Commission International de L`Eclairage (CIE) coordinate of (0.367, 0.436) at 1,000 cd/m².

We developed a package of remote phosphor structure having blue LED chips and phosphors physically separated, and the characteristics were evaluated according to different classifications of phosphor coatings. Remote phosphor was produced by screen printing coating on glass substrate with phosphor content rated paste and heat treatment. After mounting Remote phosphor, which has been classified according to number of coatings, on top of blue LED chips, luminous flux, luminous efficacy, CCT and CRI were measured. The measurement results showed the most suitable characteristics of white LED package as a general light source when the content rate of phosphor in Remote phosphor was 80 wt.% with 3 layers of coatings and thickness over 12 μm.

White light emitting diode (LED) determined the most appropriate color temperature in reading lighting evaluated fatigue degree of eye according to color temperature. The eye fatigue degrees are determined by brightness and color temperature. Therefore, we measured the results of eyes test according to the change of color temperature and brightness. Experiments except for astigmatic corrected visual acuity of 0.8 more and age 20 to 25 years old, male and female college students was conducted in 100 patients. And constant illumination conditions, visual acuity was measured by varying the color temperature. The optometry at 10 minutes in the darkroom adapted eye. And then the temperature of 25±3 degrees, the humidity was carried out at 50±5%. As a result of typical color temperature of white light (5,600 K) has identification of the readability.

We studied the emission characteristics of white phosphorescent organic light-emitting diodes (PHOLEDs), which were fabricated using a two-wavelength method. The best blue emitting OLED and red emitting OLED characteristics were obtained at a concentration of 12 vol.% FIrpic and 1 vol.% Bt2Ir(acac) in UGH3, respectively. And the optimum thickness of the total emitting layer was 25 nm. To optimize emission characteristics of white PHOLEDs, white PHOLEDs with red/blue/red, blue/red, red/blue and co-doping emitting layer structures were fabricated using a host-dopant system. In case of white PHOLEDs with co-doping structure, the best efficiency was obtained at a structure UGH3: 12 vol. % FIrpic: 1 vol.% Bt2Ir(acac) (25 nm). The maximum brightness, current efficiency, power efficiency, external quantum efficiency, and CIE (x, y) coordinate were 13,430 cd/㎡, 40.5 cd/A, 25.3 lm/W, 17 % and (0.49, 0.47) at 1,000 cd/㎡, respectively.

We studied the emission characteristics of white phosphorescent organic light-emitting diodes (PHOLEDs), which were fabricated using a two-wavelength method. To optimize emission characteristics of white PHOLEDs, white PHOLEDs with red/blue, blue/red and red/blue/red emitting layer (EML) structures were fabricated using a host-dopant system. In case of white PHOLEDs with red/blue structure, the best efficiency was obtained at a structure of red (15 nm)/blue (15 nm). But the emission color was blue-shifted white. In case of white PHOLEDs with blue/red structure, the better color purity and efficiency were observed at a blue (29 nm)/red (1 nm) structure. For additional improvement of color purity in white PHOLEDs with blue (29 nm)/red (1 nm) EMLs, we fabricated white PHOLEDs with red (1 nm)/blue (28 nm)/red (1 nm) structure. The current efficiency, external quantum efficiency, and CIE (x, y) coordinate were 27.2cd/A, 15.1%, and (0.382, 0.369) at 1,000cd/㎡, respectively.

To investigate the effect of two-emission-layer structure on the emission characteristics of the phosphorescent white organic light-emitting diodes (PHWOLEDs), the PHWOLEDs with two different emission layers, blue EML(29 nm, FIrpic-doped mCP) and red EML(1 nm, Ir(pq)2acac-doped CBP)), following host-guest system were fabricated. The bi-layered blue EML was composed of mCP:FIrpic (20 nm, 7 vol.%) and mCP:FIrpic (9 nm, 7, 10, 15, 20, and 25 vol.%, respectively). When the concentration of FIrpic was increased from 7 to 15 vol.%, light emission luminance, current efficiency, and external quantum efficiency were increased. On the contrary, when the concentration of FIrpic was increased to more than 20 vol.%, light emission luminance, current efficiency, and external quantum efficiency were decreased. The PHWOLEDs with the bi-layered blue EML structure of mCP:FIrpic (20 nm, 7 vol.%) and mCP:FIrpic (9 nm, 15 vol.%) showed current efficiency of 29.7 cd/A and external quantum efficiency (EQE) of 16.6% at 1,000 cd/cm2.

In order to investigate the emission characteristics of the phosphorescent white organic light-emitting diodes (PHWOLEDs) according to various hole transport layers (HTLs), PHWOLEDs composed of HTLs whose structure are NPB/TCTA, NPB/mCP and NPB/TCTA/mCP, two emissive layers (EMLs) which emit two-wavelengths of light (blue and red), and electron transport layer were fabricated. The applied voltage, power efficiency, and external quantum efficiency at a current density of 1 ㎃/㎠for the fabricated PHWOLEDs were 7.5 V, 11.5 lm/W, and 15%, in case of NPB/mCP, 5 V, 14.8 lm/W, and 13.7%, in case of NPB/TCTA, and 5.5 V, 14.6 lm/W, and 15%, in case of NPB/TCTA/mCP in the hole transport layer, respectively. High emission efficiency can be obtained when the amount of hole injection from anode is balanced out by the amount of electron injection from the cathode to EML by using NPB/TCTA/mCP structured HTL.