• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.336-339
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• 2002

Fluorenevinylene-based EL polymers, poly(9,9-dioctylfluorene-2,7-vinylene) (PFV) and poly[(9,9-dioctylfluorene-2,7-vinylene)-co-{2-methoxy-5-(2 ethylhexyloxy)-1,4-phenylenevinylene}] (PFV-co-MEH-PPV), have been synthesized by Gilch polymerization method. The resulting polymers were soluble in common organic solvents and easily spin cast onto the indium-tin oxide (ITO) substrate. The weight average molecular weight and polydispersity of PFV and PFV-co-MEH-PPV were in the range of 22.2 - 43.2 x $10^4$ and 1.9 - 3.0, respectively. Double-layer light-emitting diodes with ITO/PEDOT/Polymer/Al configuration were fabricated. PFV-co-MEH-PPV showed better EL properties than those of PFV and MEH-PPV The turn-on voltage of poly(9,9dialkylfluorene) derivatives were dramatically decreased to the 2.5 V compared to fluorene-based EL polymers. The maximum brightness and luminescence efficiency were up 7 to 1350 cd/$m^2$ and 0.51 Cd/A.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.193-196
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• 1999

Organic electroluminescent devices have attracted a great deal of attention due to thier potential application to full-color flat-panel displays. The 8-hydroxyquinollne Zinc(Znq$_2$) were synthesized successfully from zinc chloride(ZnCl$_2$) and zinc acetate(Zn(C$_2$H$_3$O$_3$)$_2$) as green omitting material. A double-layer ELD consist of an emitting layer of B-hydroxyquinoline Zinc(Znq$_2$) and a hole-transport layer of tai-phenylene diamine(TPD) derivatives sandwiched between an Aluminium(Al) and Indium-Tin-Oxide(ITO) electrodes omitted green light resulting from Znq$_2$. The electroluminescent devices (ELD) exhibited a maximum luminance of 1000cd/$\textrm{cm}^2$ at a driving voltage of 8V and a driving current density of 0.4mA/$\textrm{cm}^2$.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.48 no.6
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• pp.68-76
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• 2011

We introduce a parallax barrier type autostereoscopic display in order to overcome the limited viewing angle of the conventional parallax barrier type displays. The proposed method adopts a special structure of double pairs of ITO that have a common TN-LC at the core of the conventional parallax barrier. Compared with the conventional parallax barrier type displays, the proposed display uses moving parallax barriers and eye tracking system to make stereoscopic view images adapted to the movement of viewer. We implemented a prototype of the proposed dual layer parallax barrier system, and verified that the proposed autostereoscopic display maintains seamless 3D views even when a viewer's head is moving.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.974-977
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• 2003

A new series of statistical alternating EL copolymer, poly[bis{2-(4-phenylenevinylene)-2-cyanoethenyl}- 9,9-dihexyl-9H-fluorene-2,7-yl-alt-1,4-phenylene vinylene] (polymer-I) was synthesized by the modified Heck coupling reaction, and their EL characteristics were also investigated. Double layer polymer light-emitting display (PLED) with the configuration of ITO/PEDOT/polymer/Al devices show maximum brightness and luminous efficiency up to 3000 $cd/m^{2}$ at 30 V and 0.07 lm/W at 21 V, respectively.

• Macromolecular Research
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• v.15 no.3
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• pp.216-220
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• 2007

A new polyfluorene-based copolymer having 2-ethylhexyloxy-5-methoxy-l,4-phenylene as an electron donating group and 2,5-diphenyl-oxadiazole as an electron withdrawing group was synthesized by the Suzuki coupling reaction. The obtained copolymer was characterized by $^1H-NMR,\;^{13}C-NMR$, and IR-spectroscopy. The weight average molecular weight ($M_w$) of the obtained polymer was 18,600 with a polydispersity index of 1.5. The maximum photoluminescence of the solution and film of the polymer was observed at 453 nm and 456 nm, respectively. A double-layer device with the configuration, ITO/PEDOT/copolymer/Al, emitted blue light at 460 nm.

• Journal of the Korean Applied Science and Technology
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• v.21 no.1
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• pp.24-30
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• 2004

New electroluminescent materials based on anthracene chromophore with naphthylethenyl substituent, 9,10-bis($\alpha$-naphthylethenyl)anthracene (a-BNA), as well as four kinds of its derivatives were synthesized, and luminescent properties of these materials were investigated. Electrolumineecent(EL) emission band was discussed based on their substituent structure differences. It was found that the emission band strongly depends on the molecular structure of introduced substituent. It can be tuned from 557 nm to 591 nm by changing the substituent structures. On the other hand, the anthracene chromophore with bulky substituent possessed high melting point and they gave stable films through vacuum-sublimation. The double layer EL device of ITO/TPD/emission layer/Mg:Ag was employed, and exhibited efficient orange light originating from emitting materials. EL emission with a maximum luminance was observed in the b-BNA emitting material, : maximum luminance was about 8,060 cd $m^{-2}$ at an applied voltage of 10 V and current density of 680 $mA/cm^2$. In conclusion, the electroluminescent properties also showed good difference with their substituent structure.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.9
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• pp.816-825
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• 2003

Current-voltage-luminance characteristics of organic light-emitting diodes (OLEDs) were measured in the temperature range of 10 K～300 K. Indium-tin-oxide (ITO) was used as an anode and aluminum as a cathode in the device. Organic of N,N'-diphenyl-N,N'-di(m-tolyl)-benzidine (TPD) was used for a hole transporting material, and tris (8-hydroxyquinolinato) aluminum (Alq$_3$) for an electron transporting material and emissive material. And copper phthalocyanine (CuPc), poly(3,4-ethylenedi oxythiophene);poly(styrenesulfonate) (PEDOT:PSS), and poly(N-vinylcarbazole) (PVK) were used for hole-injection buffer layers. From tile analysis of electroluminescence (EL) and photoluminesccnce (PL) spectra of the Alq$_3$, the EL spectrum is more greenish then that of PL. And the temperature-dependent current-voltage characteristics were analyzed in the double and multilayer structure of OLEDS. Electrical conduction mechanism was explained in the region of high-electric and low-electric field. Temperature-dependent luminous efficiency and operating voltage were analyzed from the current-voltage- luminance characteristics of the OLEDS.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.410.2-410.2
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• 2016

Tandem structure is promising in organic solar cells because of its double open-circuit voltage (VOC) and efficient photon energy conversion. In a typical tandem device, the two single sub-cells are stacked and connected by an interconnecting layer. The fabrication of two sub-cells are usually carried out in a glovebox filled with nitrogen or argon gas, which makes it expensive and laborious. We report a glovebox-free fabricated inverted tandem organic solar cells wherein the tandem structure comprises sandwiched interconnecting layer based on p-doped hole-transporting, metal, and electron-transporting materials. Complete fabrication process of the tandem device was performed outside the glove box. The tandem solar cells based on poly(3-hexylthiophene) (P3HT) and (6,6)-phenyl C61-butyric acid methyl ester (PCBM) can realize a high VOC, which sums up of the two sub-cells. The tandem device structure was ITO/ZnO/P3HT:PCBM/PEDOT:PSS/MoO3/Au/Al/ZnO-d/P3HT:PCBM/PEDOT:PSS/Ag. The separate sub-cells were morphologically and thermally stable up to 160 oC. The high stability of the active layer benefits in the fabrication processes of tandem device. The performance of tandem organic solar cells comes from the sub-cells with an 50 nm thick active layer of P3HT:PCBM, achieving an average power conversion efficiency (PCE) of 2.9% (n=12) with short-circuit current density (JSC) = 4.26 mA/cm2, VOC = 1.10 V, and fill factor (FF) = 0.62. Based on these findings, we propose a new method to improve the performance and stability of tandem organic solar cells.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.1520-1521
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• 2008

There are several ways to demonstrate white organic light emitting diodes (OLEDs) for displays and solid state lighting applications. Among these approaches are the stacked three primary or two complementary colors light-emitting layers, multiple-doped emissive layer, and excimer and exciplex emission [1-10]. We report on white phosphorescent excimer devices by using two light emitting materials based on platinum complexes. These devices showed a peak EQE of 15.7%, with an EQE of 14.5% (17 lm/W) at $500\;cd/m^2$, and a noticeable improvement in both the CIE coordinates (0.381, 0.401) and CRI (81). Devices with the structure ITO/PEDOT:PSS/TCTA (30 nm)/26 mCPy: 12% FPt (10 nm) /26 mCPy: 2% Pt-4 (15 nm)/BCP (40 nm)/CsF/Al [device 1], ITO/PEDOT:PSS/TCTA (30 nm)/26 mCPy: 2% Pt-4 (15 nm)/26 mCPy: 12% FPt (10 nm)/BCP (40 nm)/CsF/Al [device 2], and ITO/PEDOT:PSS/TCTA (30 nm)/26 mCPy: 2% Pt-4: 12% FPt (25 nm)/BCP (40 nm)/CsF/Al [device 3] were fabricated. In these cases, the emissive layer was either the double-layer of 26 mCPy:12% FPt and 15 nm 26 mCPy: 2% Pt-4, or the single layer of 26mCPy with simultaneous doping of Pt-4 and FPt. Device characterization indicates that the CIE coordinates/CRI of device 2 were (0.341, 0.394)/75, (0.295, 0.365)/70 at 5 V and 7 V, respectively. Significant change in EL spectra with the drive voltage was observed for device 2 indicating a shift in the carrier recombination zone, while relatively stable EL spectra was observed for device 1. This indicates a better charge trapping in Pt-4 doped layers [10]. On the other hand, device 3 having a single light-emitting layer (doped simultaneously) emitted a board spectrum combining emission from the Pt-4 monomer and FPt excimer. Moreover, excellent color stability independent of the drive voltage was observed in this case. The CIE coordinates/CRI at 4 V ($40\;cd/m^2$) and 7 V ($7100\;cd/m^2$) were (0.441, 0.421)/83 and (0.440, 0.427)/81, respectively. A balance in the EL spectra can be further obtained by lowering the doping ratio of FPt. In this regard, devices with FPt concentration of 8% (denoted as device 4) were fabricated and characterized. A shift in the CIE coordinates of device 4 from (0.441, 0.421) to (0.382, 0.401) was observed due to an increase in the emission intensity ratio of Pt-4 monomer to FPt excimer. It is worth noting that the CRI values remained above 80 for such device structure. Moreover, a noticeable stability in the EL spectra with respect to changing bias voltage was measured indicating a uniform region for exciton formation. A summary of device characteristics for all cases discussed above is shown in table 1. The forward light output in each case is approximately $500\;cd/m^2$. Other parameters listed are driving voltage (Bias), current density (J), external quantum efficiency (EQE), power efficiency (P.E.), luminous efficiency (cd/A), and CIE coordinates. To conclude, a highly efficient white phosphorescent excimer-based OLEDs made with two light-emitting platinum complexes and having a simple structure showed improved EL characteristics and color properties. The EQE of these devices at $500\;cd/m^2$ is 14.5% with a corresponding power efficiency of 17 lm/W, CIE coordinates of (0.382, 0.401), and CRI of 81.

• Bulletin of the Korean Chemical Society
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• v.30 no.9
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• pp.1933-1938
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• 2009

New $\pi$-conjugated polymer with vinylene linkage, poly((10-hexyl-3,7-phenothiazine)-alt-(4-(4-butyl-phenyl)- 3,5-diphenyl-4H-[1,2,4]triazole)-3,5-vinylene) (PTV-TAZ) was synthesized by the Heck coupling reaction. The photoluminescence (PL) maximum wavelength and the band gap energy of PTV-TAZ film were 555 nm and 2.41 eV, respectively. The HOMO energy level of PTV-TAZ was -4.99 eV, which was slightly lower than that of PTV (-4.89 eV). Electron deficient aromatic 1,2,4-triazole (TAZ) in the polymer backbone does not affect the HOMO energy level significantly. The maximum efficiency and brightness of double layer structured electroluminescent (EL) device (ITO/PEDOT (30 nm)/PTV-TAZ (60 nm)/Al) were 0.247 cd/A and 553 cd/$m^2$, respectively, which were significantly higher than those of the device based PTV (1.65 ${\times}\;10^{-4}$ cd/A and 4.3 cd/$m^2$). This is due to that TAZ unit improves electron transporting ability in the emissive layer. The turn-on voltage (defined as the voltage required to give a luminescence of 1 cd/$m^2$) of brightness of the device based on PTV-TAZ was 12.0 V, which was similar to that the based on PTV (11.5 V). This is due to that the ionization potential of PTV-TAZ is very similar to that of PTV.