• Journal of the Korean institute of surface engineering
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• v.47 no.4
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• pp.210-214
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• 2014

We investigated emission characteristics of tandem organic light emitting devices (OLEDs) with p-type materials as charge generation layer. The tandem OLEDs were fabricated by using $MoO_x$, $WO_x$, C60 and HATCN as p-type material or not using p-type material for charge generation. When HATCN was used as p-type material, it showed high current density at low applied voltage, but increase of efficiency was small because of charge unbalance in emitting layer. In case of tandem OLED not using p-type material, applied voltage increased remarkably because of difficulty of hole injection. In case of $MoO_x$, $WO_x$ or C60 as p-type material, current emission efficiency increased greatly. In particular, current emission efficiency of tandem OLED using $MoO_x$ as p-type material increased up to 3 times than current emission efficiency of single OLED. The Commission Internationale de l'Eclairage (CIE) 1931 color coordinates were changed by overlapping of 504 nm emission wavelength. As a result, emission efficiency of tandem OLED improved compared with single OLED, but driving voltage also increased by increase of organic layer thickness.

• Journal of the Korean institute of surface engineering
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• v.48 no.3
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• pp.105-109
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• 2015

We studied emission characteristics of blue fluorescent multi-tandem OLEDs using $Al/MoO_x$ as charge generation layer(CGL). Threshold voltage for 2, 3, 4, and 5 units tandem OLEDs was 8, 11, 14 and 18 V, respectively. The threshold voltage in multi-tandem OLEDs was lower than multiple of 4 V for the single OLED. Maximum current efficiency and maximum quantum efficiency of single OLED were 7.6 cd/A and 5.5%. Maximum current efficiency for 2, 3, 4, and 5 units tandem OLEDs was 22.6, 31.4, 41.2, and 46.6 cd/A, respectively. Maximum quantum efficiency for 2, 3, 4, and 5 units tandem OLEDs was 11.8, 15.8, 21.8, and 25.6%, respectively. The maximum current efficiency and maximum quantum efficiency in multi-tandem OLEDs were higher than multiple of those for the single OLED. The intensity for 508 nm peak was changed and the peak wavelength was red shift by increase of tandem unit in electroluminescent emission spectra. These phenomena can be caused by micro-cavity effect with increasing of organic layer thickness.

• Electrical & Electronic Materials
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• v.7 no.5
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• pp.409-416
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• 1994

A double layered photoreceptor using phthalocyanine dye was made by dip-coating method. The under cutting layer(UCL) was coated with A1$\_$2/O$\_$3/ or polyamide, and the charge generation layer(CGL) was formed by .tau.-type metal-free phthalocyanine. The oxadiazole was used as a charge transport layer(CTL) and polycarbonate and poly(vinyl butyral) was employed as a host polymer. The .tau.-H$\_$2/Pc had an absorption peak around 780nm, which coincided with the emitting wavelengths of GaAlAs diode lasers. Maximum charge acceptance of CTL that gives thickness of 12.mu.m was -900V by corona charge of -6.0kV. In photo-induced discharge measurements, residual potential was less than -20V and sufficient for ordinary use, and sample films using of poly(vinyl butyral) was showed good charge retention. In printing test, drum that was employed polycarbonate as a host polymer showed the good print quality.

• Journal of the Korean institute of surface engineering
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• v.47 no.3
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• pp.104-108
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• 2014

To improve emission efficiency of organic light emitting devices (OLEDs), we fabricated the tandem OLED of ITO / 2-TNATA / NPB / SH-1: 3 vol.% BD-2 / Bphen / Liq / Al / $MoO_x$ (X nm) / 2-TNATA / NPB / SH-1: 3 vol.% BD-2 / Bphen / Liq / Al structure. And emission properties of single OLED and tandem OLED with $MoO_x$ thickness as charge generation layer (CGL) were measured. The current emission efficiency and quantum efficiency of tandem OLED with $MoO_x$ of 3 nm thickness were improved compare with single OLED from 7.46 cd/A and 5.39% to 22.57 cd/A and 11.76%, respectively. In case of thicker or thinner than $MoO_x$ of 3~5 nm, the current emission efficiency and quantum efficiency were decreased, because balance of electron and hole in emission layer was not matching. The driving voltage was increased from 8 V of single OLED to 15 V of tandem OLED by thickness increase of OLED. As a result, it was possible to improve the emission efficiency of OLEDs by optimized $MoO_x$ thickness.

• Proceedings of the KAIS Fall Conference
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• 2010.11a
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• pp.359-362
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• 2010

본 논문에서는 적층형 백색유기발광 조명소자를 제작하여 단층형 구조와 비교 분석하는 연구와 CGL(Charge Generation Layer)의 두께 변화에 따른 소자특성 연구를 하였다.

• Korean Journal of Materials Research
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• v.7 no.5
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• pp.403-410
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• 1997

본 연구는기존의 보고에서 보다 감광화효율을 더욱 향상시키기 위하여 결정형이 다른 전하발생물질 (CGM:Charge Generation Material)과 전하수송물질(CTM:Charge Transport Material)을 사용하여 감광체를 만들었고, 이들의 정전특성을 비교검토하였다. 전하발생물질로서 결정형이 다른 $\alpha$-, $\beta$-, x-형 무금속 프탈로시아닌 (H$_{2}$Pc)을 사용한 결과, x-H$_{2}$Pc를 사용한 감광체의 감도는 E$_{1}$2/의 값이 2.62 $\mu$J/$\textrm{cm}^2$로 가장 두수하게 나타났다. 전하발생층(CGL:Charge Generation Layer)에 첨가되는 CGM-CTM, CGM-CTM-ZnO로 구성된 감광체보다 전하발생층에 전하발생계만으로 구성된 감광체의 경우의 전하유지율 (80%) 및 감도(E$_{1}$2/=2.83$\mu$J/$\textrm{cm}^2$)면에서 우수함을 보여주었다. 한편 binder로서 PVB-co-PVA-co-PVA$_{c}$[poly(viny1 butyral-co-viny1 alcohol-co-viny1 acetate)]를 사용했을 때는, CGM-CTM으로 구성된 감광체보다 CGL에 CGM-CTM으로 구성된 감광체의 경우의 전하유지율(71%) 및 감도(E$_{1}$2/=2.62$\mu$J/$\textrm{cm}^2$)면에서 우수함을 보여주었다.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.4
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• pp.53-60
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• 1998

The purpose of this paper is to meausre the electrophotographic characteristics of double-layered organic photoreceptor and to evaluate an application for the laser beam printer drum. The characte carrier generation layer(CGL) of double-layered photoreceptor was fabricated with .tau.-H$_{2}$Pc which has high photosensitivity in the near-infrareed region(thickness is about 0.3.mu.m), and Oxadiazole derivative was chosen as a charge carrier transport layer(CTL) because of its high hole mobility. To observe the electrophotographic characteristics of the photoreceptor, we measured the charge acceptance, dark-decay ratio, residual potential after light irradiation. From the result of this study, proper thickness of CTL was about 10.mu.m. Also it's realized that electrophotographic characteristics of the photoreceptor were depend on the thickness of the CTL and the initial surface potential.

• Journal of the Korean Institute of Telematics and Electronics T
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• v.36T no.3
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• pp.19-25
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• 1999

The photoreceptor films with double layer structure were prepared by the plasma polymerization and the dip-coating method. The blocking layer was coated with A1$_2$O$_3$ on the Al substrate and the charge generation layer was formed by H$_2$ phthalocyanine (H$_2$Pc). Poly 9-Vinylcarbazole was used as a charge transport layer. H$_2$Pc film prepared by the vacuum evaporation had absorption peaks on 613.6[nm] and 694.8[nm], and H$_2$Pc film prepared by the plasma polymerization had a dull peaks between 600 and 700[nm]. The surface potential of PVCz increased with increasing the applied voltage and the thickness of PVCz. The dark decay characteristic, the light decay time and the residual time increased with increasing the thickness of PVCz. The surface charge of PVCz of 15[${\mu}{\textrm}{m}$] thickness was 134[nc/$\textrm{cm}^2$] at the surface potential of -600[V] and the charge generation efficiency of H$_2$Pc was 0.034.