Jae Sang Lee

Abstract Since their introduction over 15 years ago, the operational lifetime of blue phosphorescent organic light-emitting diodes (PHOLEDs) has remained insufficient for their practical use in displays and lighting. Their short lifetime results from annihilation between high-energy excited states, producing energetically hot states (>6.0 eV) that lead to molecular dissociation. Here we introduce a strategy to avoid dissociative reactions by including a molecular hot excited state manager wit

We demonstrate threefold directional light concentration from an organic light-emitting diode luminaire for use in spot lighting and other applications where high intensity illumination is required. The concentrating luminaire comprises four triangular, large-area green electrophosphorescent organic light emitting diodes (PHOLEDs) deposited on plastic substrates and assembled into a pyramidal structure with an open base that serves as the light exit aperture. The PHOLED surfaces are highly refle

Organic light-emitting diodes (OLEDs) of all kinds inevitably undergo permanent performance degradation over time, leading to burn-in in the displays made with the OLEDs. To compensate for display burn-in and extend product lifetimes, having a model that can precisely predict OLED degradation is most essential. In this work, we review a few select studies that focused on the physics-based analysis and modeling of OLED degradation. The framework and features of the lifetime models based on the ph

연구배경: 흡연 관련 질환의 발생을 줄이기 위하여 장기 금연 이 필수적이지만 금연 기간이 길어질수록 금연 유지 비율은 감소한다. 2년 이상 장기 금연 유지 및 관련 요인에 대한 연구 는 드물다. 장기적이고 효과적인 금연 치료를 위하여, 금연 후 재흡연율 및 관련 요인을 평가하였다. 방법: 1995년 1월부터 2006년 12월까지 일개 건강검진센터를 두 차례 이상 방문한 수진자 중 최초 방문 후 금연에 성공한 사 람들을 대상으로 전화 설문 및 의무 기록 분석을 시행하였다. 의무 기록과 전화 설문 결과가 일치하는 총 308명을 대상으로 최대 금연 기간 및 재흡연 여부와 금연 동기, 방문 전 금연 성공 회수 등 관련 요인을 평가하였다. 결과: 308명의 평균 추적 관찰 기간은 9년 4개월이었고, 첫 방 문 시 평균 연령은 47.9세였다. 최대 금연 기간의 중간값은 5.50 년이었고, 금연 기간이 2년 이상 7년 미만인 경우 연간 재흡연 율은 2.5-4.2%이었다. 평균 흡연 시작 연령은

This paper describes the development and performance of a vision system, named PFSS (path finder smart sensor) for autonomous navigation of an unmanned ground vehicle. A monocular camera and vision processing algorithms were used as the sensor system to identify traversable terrain. Unlike the Bayesian based method which was used by Team CIMAR in the 2005 DARPA Grand Challenge, the expectation-maximization (EM) algorithm is applied. The implementation and performance of this approach are reporte

Remote plasma atomic layer deposited (RPALD) Al2O3 films were investigated to apply as tunnel and blocking layers in the metal-oxide-semiconductor capacitor memory utilizing Au nanocrystals (NCs) for nonvolatile memory applications. The interface stability of an Al2O3 film deposited by RPALD was studied to observe the effects of remote plasma on the interface. The interface formed during RPALD process has high oxidation states such as Si+3 and Si+4, indicating that RPALD process can grow more st

Toward the development of an energy-efficient artificial neuron device, a study of the mechanism of electroforming in OTS and mitigation of the electroforming by doping Sn in GeSe was conducted.

Augmented reality (AR) applications require displays with an extended color gamut to facilitate the presentation of increasingly immersive content. The waveguide (WG) display technology, which is typical AR demonstration method, is a critical constraint on the color gamut of AR systems because of the intrinsic properties of the holographic optical elements (HOEs) used in this technology. To overcome this limitation, we introduce a method of spatially modulated diffractive optics that can expand

Organic light-emitting diodes (OLEDs) are an important technology for attractive, high efficiency displays and lighting. The primary impediment to large-scale commercialization of OLEDs is the short operational lifetime of blue-emitting devices. The key to realizing long-lived blue PHOLEDs is to prevent the hot state energies from ever leading to molecular dissociation reactions in the first place. The small- and large-energy gap defects are identified as the hole traps. Materials used in the PH

In augmented reality (AR), focal accommodation for real objects and augmented imagery is essential for comfortable viewing, and this requires a depth of field (DoF) in AR displays. Wide DoFs have been achieved in various display systems, but these systems are often bulky, highly power-consuming, and computationally complex. Hence, we propose a simple and effective optical method to extend the DoF in AR displays. The proposed method harnesses a focus tuning block consisting of a multifocal lens (

Coupling between the electric field, magnetic field, and strain of composite materials is achieved when electro-elastic (piezoelectric) and magneto-elastic (piezomagnetic) particles are joined by an elastic matrix. Although the matrix is neither piezoelectric nor piezomagnetic, the strain field in the matrix couples the E field of the piezoelectric phase to the B field of the piezomagnetic phase. This three-phase electro-magneto-elastic composite should have greater ductility and formability tha

Despite recent advancements in augmented reality (AR) displays, conventional AR head-mounted displays (HMD) lack comfort due to heat and size, which hinders daily use. To address these issues, we propose an approach for AR-HMD optics that uses a multicore fiber (MCF) to transfer virtual content from a light engine in the user’s pocket to an eyepiece. This allows the HMD to avoid heat generation and maintain a compact form factor. In this work, we design and demonstrate MCF-relayed AR optics in t