• 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.

• 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 Ceramic Society
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• v.52 no.4
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• pp.294-298
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• 2015

Blocking layers with nano carbon blacks (NCBs) were prepared by adding 0.0 ~ 0.5 wt% NCBs to the $TiO_2$ blocking layer. Then, dye sensitized solar cells (DSSCs) were fabricated with a $0.45cm^2$ active area. TEM and micro-Raman spectroscopy were used to characterize the microstructure and phases of the NCBs, respectively. Optical microscopy and AFM were used to analyze the microstructure of the $TiO_2$ blocking layer with NCBs. UV-VIS-NIS spectroscopy was used to determine the band gap of the $TiO_2$ blocking layer with NCBs. A solar simulator and potentiostat were used to determine the photovoltaic properties and impedance of DSSCs with NCBs. The energy conversion efficiency (ECE) increased from 3.53 to 6.20 % when the NCB content increased from 0.0 to 0.3 wt%. This indicates that the effective surface area and electron mobility increased in the $TiO_2$ blocking layer with NCBs. However, the ECE decreased when the NCB content was increased to over 0.4 wt%. This change occurred because the effective electron transport area decreased with the addition of excessive NCBs to the $TiO_2$ blocking layer. The results of this study suggest that the ECE of DSSCs can be enhanced by adding the appropriate amount of NCBs to the $TiO_2$ blocking layer.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.219-219
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• 2013

The effect of an electron blocking layer (EBL) on V-I curves in GaN/InGaN multiple quantum well is investigated. For the first time, we found that curves were intersected at 3.012 V and analyzed the reason for intersection. The forward voltage in LEDs with an p-AlGaN EBL is larger than without p-AlGaN EBL at low injection current because the Mg doping efficiency for p-GaN layer was higher than that of p-AlGaN layer. However, the forward voltage in LEDs with an p-AlGaN EBL is smaller than without p-AlGaN EBL at high injection current because the carriers overflow from the active layer when injection current increases in LEDs without p-AlGaN EBL and in case of LED with p-AlGaN EBL, the carriers are blocked by EBL.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.05a
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• pp.686-689
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• 2012

In this paper, the GaN-based LED characteristics are analyzed using ISE-TCAD. The LED consists of GaN barriers, active region of InGaN quantum well, AlGaN EBL(Electron Blocking Layer) and AlGaN HBL(Hole Blocking Layer) on GaN buffer layer. The output power characteristics of LED considering Auger recombination rate, thickness of quantum well and number of quantum wells are analyzed and some criteria for the design of LED are proposed.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.10a
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• pp.251-254
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• 2012

In this paper, the output characteristics of GaN-based LED considering quantum well structure 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 thickness of quantum well, number of quantum well and doping of barrier are analyzed using ISE-TCAD.

• 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 Sensor Science and Technology
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• v.33 no.4
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• pp.224-229
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• 2024

Quantum dot light-emitting diodes (QD-LEDs) are emerging as next-generation displays owing to their high color purity, wide color gamut, and solution processability. Enhancing the efficiency of QD-LEDs involves preventing non-radiative recombination mechanisms, such as Auger and interfacial recombination. Generally, ZnO serves as the electron transport layer, which is known for its higher mobility compared to that of organic semiconductors and can lead to excessive electron injection. Some of the injected electrons pass through the quantum dot emissive layer and undergo non-radiative recombination near or within the organic hole transport layer (HTL), resulting in HTL degradation. Therefore, the implementation of electron blocking layers (EBLs) is essential; however, studies on all-solution-processed inverted InP QD-LEDs are limited. In this study, poly(9-vinylcarbazole) (PVK) is introduced as an EBL to mitigate HTL degradation and enhance the emission efficiency of inverted InP QD-LEDs. Using a single-carrier device, PVK was confirmed to effectively inhibit electron overflow into the HTL, even at extremely low thicknesses. The optimization of the PVK thickness also ensured minimal disruption of the hole-injection properties. Consequently, a 1.5-fold increase in the maximum luminance was achieved in the all-solution-processed inverted InP QD-LEDs with the EBL.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.217-217
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• 2012

Solution-processed tungsten oxide thin film with thickness of about 30 nm is prepared from ammonium tungstate. This layer is introduced into the interface between the poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) layer and the ITO electrode to be used as an electron blocking layer. The annealed tungsten oxide thin films at $150^{\circ}C$ and $300^{\circ}C$ show amorphous phase, while the $400^{\circ}C$ -annealed tungsten oxide film shows crystalline phase. At $150^{\circ}C$ annealing temperature, the conversion efficiency is significantly improved from 0.71% to 1.42% as the condition is changed from vacuum to air atmosphere, which is related to oxidation state of tungsten in amorphous phase. For the air annealing condition, the conversion efficiency is further increased from 1.42% to 2.01% as the temperature is increased from $150^{\circ}C$ to $300^{\circ}C$, which is mainly due to the removal of the chemisorbed water. However, a slight deterioration in photovoltaic performance is observed when the temperature is increased to $400^{\circ}C$, which is ascribed to poor electron blocking ability due to the formation of crystalline phase. It is concluded that $W^{6+}$ oxidation state and amorphous nature in tungsten oxide interlayer is essential for blocking electron effectively from the active layer to the ITO electrode.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.53.2-53.2
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• 2011

Dye-sensitized solar cells(DSSCs) have been recognized as an alternative to the conventional p-n junction solar cells because of their simple fabrication process, low production cost, and transparency. A typical DSSC consists of a transparent conductive oxide (TCO) electrode, a dye-sensitized oxide semiconductor nanoparticle layer, liquid redox electrolyte, and a Pt-counter electrode. In dye-sensitized solar cells, charge recombination processes at interfaces between coducting glass, $TiO_2$, dye, and electrolyte play an important role in limiting the photon-to-electron conversion efficiency. A layer of ZTO thin film less than ~200nm in thickness, as a blocking layer, was deposited by DC magnetron sputtering method directly onto the anode electrode to be isolated from the electrolyte in dye-sensitized solar cells(DSCs). This is to prevent the electrons from back-transferring from the electrode to the electrolyte ($I^-/I_3^-$). The presented DSCs were fabricated with working electrode of Ga-doped ZnO glass coated with blocking ZTO layer, dye-attached nanoporous $TiO_2$ layer, gel electrolyte and counter electrode of Pt-deposited GZO glass. The effects of blocking layer were studied with respect to impedance and conversion efficiency of the cells.