• 한국고분자학회:학술대회논문집
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• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
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• pp.235-235
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• 2006

Triphenylamine derivatives play important roles as hole transporting materials in organic light emitting devices. However, low molecular weight triphenylamine derivatives show low glass transition temperature and aggregation behavior, and the vapor deposition step of low molecular weight materials is incompatible with large area display fabrication. Conventional polymer PEDOT-PSS HTL has serious drawbacks such as the ITO anode corrosion, poor surface energy match with aromatic EMLs. To solve these problems, we introduced crosslinkable units to triphenylamine-based polymers to make insoluble HTL by thermal curing following spin-coating. Electrochemical and optical properties of the new hole transporting materials were investigated. In addition, the device characteristics obtained with new hole transporting polymers were investigated in details.

• 한국전기전자재료학회논문지
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• 제27권5호
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• pp.307-311
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• 2014

Because of a waveguiding effect and total internal reflection caused by a difference in refractive indices, only 20% of generated light is emitted to the air and the rest is trapped or absorbed in the device. An improvement of outcoupled efficiency of organic light-emitting diodes was studied using a microlens array. Mold of microlens array was fabricated by using photo-lithography with the AZ9260 photoresist, and the microlens array was formed onto the glass substrate using the UV curing agent named ZPU13-440. Device structure consists of microlens/glass/ITO/TPD/$Alq_3$/LiF/Al. It was found that there is an improvement of external quantum efficiency by about 20% at the same current density for the device with the microlens array compared to that of the reference one. Simulated outcoupled efficiency shows the improvement by about 20% for the device with the microlens array compared to that of the reference one. These results are consistent with the experimental ones.

• 한국전기전자재료학회논문지
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• 제34권1호
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• pp.44-49
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• 2021

Recently, infrared (IR) and near-infrared (NIR) light-emitting diodes (LEDs) were widely used for home medical applications owing to its low output power and wide exposed area for curing. For deep penetration of the light under the skin, multiple LEDs with wavelengths of 700~10,000 nm were located on a flexible printed circuit board. When multiple wavelengths of LEDs were soldered on a circuit board, the lifetime of LED module highly depends on LEDs with a short lifetime. The mean time to failure (MTTF) was able to calculate with the experimental results under high temperature and the Arrhenius model. The results of this study could help companies to approve the warranty of LED modules and its product.

• 대한소아치과학회지
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• 제41권2호
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• pp.152-156
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• 2014

최근 도입된 광범위 스펙트럼의 발광 다이오드 광중합기는 4개의 램프로 구성되어 있으며 다양한 중합 모드를 가지고 있다. 이 연구는 광범위 스펙트럼 발광 다이오드($VALO^{(R)}$, Ultradent, USA) 광중합기와 기존의 발광 다이오드 광중합기 ($Elipar^{TM}$ Freelight 2, 3M ESPE, USA)의 효율을 미세경도 시험을 통해 비교하였다. 연구에 사용한 광중합기는 $VALO^{(R)}$와 $Elipar^{TM}$ Freelight 2이며 중합 시간은 제조사의 지시에 따랐다. $37^{\circ}C$의 생리식염수에 중합된 레진 시편을 24시간 동안 보관한 후 미세경도 시험을 시행하였다. 시편 상부와 하부의 복합레진 미세경도는 공분산분석을 시행하였다. 광범위 스펙트럼의 발광 다이오드 광중합기를 이용하여 고성능 모드에서 4초, 플라즈마 모드에서 20초 광중합을 실시한 복합레진 시편의 상부는 기존의 발광 다이오드 광중합기에 비해 미세경도가 증가하였으나(p < 0.05), 시편의 하부에서는 실험에 사용된 광중합기 간에 유의성 있는 차이를 보이지 않았다.