• Journal of the Korean Applied Science and Technology
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• v.17 no.2
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• pp.120-125
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• 2000

The tfTZ(4,4',4''-trifluoro-triazine) was used as a hole blocking material for the electroluminescent devices(ELDs) in this study. In general, the holes are outnumbered the electrons in hole transport and emitting layers because the hole transport is more efficient in most organic ELDs. The hole blocking layer are expected to control the excess holes to increase the recombination of holes and electrons and to decrease current density. The former study using the 2,4,6-triphenyl-1,3,5-triazine(TTA) as hole blocking layer showed that the TTA did not form stable films with vapor deposition technique. The tfTZ can generate stable evaporated films, moreover the fluorine group can lower the highest occupied molecular orbital(HOMO) level, which produces the energy barrier for the holes. The tfTZ has high electron affinities according to the data by the Cyclic-Voltammety(CV) method, which is developed for the measurement of HOMO and lowest occupied molecular orbital(LUMO) level of organic thin films. The lowered HOMO level is made the tfTZ to be applied for a hole blocking layer in ELDs. We fabricated multilayer ELDs with a structure of ITO/hole blocking layer(HBL)/hole transporting layer(HTL)/emitting layer/electrode. The hole blocking properties of this devices is confirmed from the lowered current density values compared with that without hole blocking layer.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.442-443
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• 2007

We have studied new hole blocking layer for effective organic light emitting diodes. The device having a structure of ITO/2TNATA/$\alpha$-NPD/DPVBi : Rubrene(0.7%)/DPVBi/New Hole Blocking layer or BCP/$Alq_3$/LiF/Al has been used. The driving voltage of OLED with BCP(2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline) or New HBL were 5.5V and 4.4V, respectively. As a result, new HBL rather than BCP has a good hole blocking ability.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.310.2-310.2
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• 2013

For enhancement of dye-sensitized solar cell performance, TiO2 blocking layer has been used to prevent recombination between electron and hole at the conducting oxide and electrolyte interface. In solid state dye-sensitized solar cells, it is necessary to fabricate pin-hole free TiO2 blocking layer. In this work, we deposited the TiO2 blocking layer on conducting oxide by atomic layer deposition and compared the efficiency. To compare the efficiency, we fabricate solid state dye-sensitized solar cell with using CuSCN as hole transport material. We see the efficiency improve with 40nm TiO2 blocking layer and the TiO2 blocking layer morphology was characterized by SEM. Also, we used this blocking layer in TiO2/Sb2S3/ CuSCN solar cell.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.12
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• pp.1139-1142
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• 2005

Recently, organic light emitting diodes(OLEDs) is widely used as one of the information display techniques. We synthesized 2-(2-hydroxyphenyl)benzoxazole($Zn(HPB)_2$). We studied the luminescent properties of OLEDs using $Zn(HPB)_2$. The ionization potential(IP) and the electron affinity(EA) of $Zn(HPB)_2$ investigated using cyclic-voltammetry(C-V). The IP and EA were 6.5 eV and 3.0 eV, respectively. The PL and EL spectra of $Zn(HPB)_2$ were observed at the wavelength of 450 nm. We used $Zn(HPB)_2$ as an emitting layer and hole blocking layer. At the experiment about hole blocking effect, we inserted $Zn(HPB)_2$ between emiting material layer(EML) and cathode, and between hole transport layer(HTL) and emitting material layer(EML). We measured current density-voltage and luminance-voltage characteristics at room temperature.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.447-448
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• 2005

Recently, organic light emitting diodes(OLEDs) is widely used as one of the information display techniques. We synthesized 2-(2-hydroxyphenyl)benzoxazole($Zn(HPB)_2$). We studied the luminescent properties of OLEDs using $Zn(HPB)_2$. The ionization potential(IP) and the electron affinity(EA) of $Zn(HPB)_2$ investigated using cyclic-voltammetry(C-V). The JP, EA and Eg were 6.5eV, 3.0eV and 3.5eV, respectively. The PL and EL spectra of $Zn(HPB)_2$ were observed at the wavelength of 4S0nm. We used $Zn(HPB)_2$ as an emitting layer and hole blocking layer. At the experiment about hole blocking effect, we inserted $Zn(HPB)_2$ between emitting material layer(EML) and cathode, and hole transport layer(HTL) and emitting material layer(EML). We measured current density-voltage and luminance-voltage characteristics at room temperature.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.499-501
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• 2002

본 연구에서는 ETL층으로 널리 알려져 있는 PBD(2-(4-biphenyl)-5-(4-tert-butylphenyl) -1.3,4oxadiazole)를 HBL(Hole-blocking layer) 물질로 이용 하고 Nile red를 사용하여 적색 발광의 EL(electroluminescence) 소자를 제작 평가하였다. 일반적인 유기 EL 소자의 구조인 Anode/HTL(Hole Transport Layer)/ETL(Electron Transport Layer)/Cathode로 이루어져 있다. 여기에 HTL과 ETL사이에 HBL를 추가하여 EL 소자의 성능을 향상 시킬 수 있으면, 이러한 구조의 최종 소자를 제작 EML(emitting layer; Nile red)의 두께 및 임계전압을 달리 하여 소자 의 특성을 평가 연구 하였다.

• Journal of the Semiconductor & Display Technology
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• v.7 no.2
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• pp.49-53
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• 2008

The yellow base polymer light emitting diodes(PLEDs) with double emission and hole blocking layers were prepared to improve the light efficiency. ITO(indium tin oxide) and PEDOT : PSS[poly(3,4-ethylenedioxythiophene) : poly(styrene sulfolnate)] were used as cathode and hole transport materials. The PFO[poly(9,9-dioctylfluorene)] and MEH-PPV[poly(2-methoxy-5(2-ethylhe xoxy)-1,4-phenylenevinyle)] were used as the light emitting host and guest materials, respectively. TPBI[Tpbi1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene] was used as hole blocking layer. To investigate the optimization of device structure, we prepared four kinds of PLED devices with different structures such as single emission layer(PFO : MEH-PPV), two double emission layer(PFO/PFO : MEH-PPV, PFO : MEH-PPV/PFO) and double emission layer with hole blocking layer(PFO/PFO : MEH-PPV/TPBI). The electrical and optical properties of prepared devices were compared. The prepared PLED showed yellow emission color with CIE color coordinates of x = 0.48, y = 0.48 at the applied voltage of 14V. The maximum luminance and current density were found to be about 3920 cd/$m^2$ and 130 mA/$cm^2$ at 14V, respectively for the PLED device with the structure of ITO/PEDOT : PSS/PFO/PFO : MEH-PPV/TPBI/LiF/Al.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.12
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• pp.837-840
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• 2014

Novel materials of $Zn(HPB)_2$ and Ir-complexes were respectively synthesized as blue or red emitting material. White Organic Light Emitting Diodes (OLED) were fabricated by using $Zn(HPB)_2$ for a blue emitting layer, Ir-complexes for a red emitting layer and $Alq_3$ for a green emitting layer. White OLED was fabricated by using double emitting layers of $Zn(HPB)_2$ and $Alq_3:Ir$-complexes, and hole blocking layer of BCP. We also varied the thickness of BCP. When the thickness of BCP layer was 5 nm, white emission was achieved. We obtained a maximum luminance of $3,500cd/m^2$. 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.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.10a
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• pp.233-236
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• 2012

In this paper, the output characteristics of GaN-based LED considering blocking layer design variables are analyzed. The basic structure of the LED consists of active region of GaN barrier and InGaN quantum well between AlGaN EBL(Electron Blocking Layer) and AlGaN HBL(Hole Blocking Layer) on GaN buffer layer. The output power, internal quantum efficiency characteristics of LED active region considering Al mole fraction of EBL, thickness of EBL, Al mole fraction of HBL and doping concentration of HBL are analyzed using ISE-TCAD.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.1
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• pp.83-88
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• 2004

BAlq was fabricated as for hole blocking layer in the OLED devices to investigate its electrical and optical characteristics. Device structure was ITO/$\alpha$ -NPD/EML/BAlq/Alq3/Al:Li using TYG-201, DPVBi (4, 4 - Bis (2, 2 - diphenylethen-1 - yls) - Biphenyl), Alq and DCJTB (4-(dicyanomethylene)-2- (1-propyls)6-methy 4H-pyrans) as green emitting material, blue emitting material, host material for red emission and red emitting guest material respectively. The OLED device showed optimum working voltage and electron density at 600 cd/$m^2$ when thickness of BAlq is 25$\AA$ for RGB OLED devices while their efficiencies are better at 50$\AA$ of BAlq. Red and blue color OLEDs also fabricated using 30$\AA$ thickness of BAlq and compared with those without BAlq layer. BAlq was more effective in electrical properties such as working voltage, current density and efficiency of red OLED than blue and green ones. This study describes that 30$\AA$ is optimum thickness of BAlq for best performance of full color OLED devices when using BAlq as a hole blocking material.