• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2002년도 International Meeting on Information Display
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• pp.340-343
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• 2002

We report here our recent progress in the development and commercialization of polyfluorenes emitting red, green and blue (ROB) colors as materials for light emitting diodes (LEDs). Our patented version of the Suzuki coupling process has been used to synthesize a variety of fluorenebased homopolymers and copolymers emitting colors across the entire visible spectrum. The optical and electronic properties of the polymers are tailored through selective incorporation of different aromatic units into the polyfluorene backbone. Our latest green emitter, reported herein, provides very efficient devices with a low turn-on voltage of 2.25 V, a peak efficiency of 10.5 Cd/A at 6,600 Cd/$m^2$ at 4.85 V. These devices maintain an efficiency of greater than 10 Cd/A up to 50,000 Cd/$m^2$ and demonstrate very good stability as exemplified by a device half-life of greater than 1,500 hours starting from 1,100 Cd/$m^2$. Considerable progress has also been made with red and blue emitters and will be the subject of this presentation.

• 생명과학회지
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• 제32권7호
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• pp.578-587
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• 2022

우리나라는 세계 7위의 온실가스 배출국가로서 국제적으로 배출량 규제가 강화됨에 따라 국가 온실가스 감축 목표를 상향하였고 이로 인해 산업계를 포함한 사회 전반적인 탄소 감축의 노력이 절실한 상황이다. 기후변화 완화 또는 적응 계획의 중요 이행 수단으로 연안과 해양생태계를 자연기반 해법(nature-based solutions, NbS)으로 활용 가능하게 되면서 최근 블루카본(blue carbon) 생태계가 주목받고 있다. 블루카본은 대기 중 이산화탄소가 광합성작용을 통해 맹그로브, 염습지 및 해초류와 같은 연안 생태계나 해조류와 미세조류와 같은 해양생태계에 의해 바이오매스로 흡수된 뒤 퇴적되어 장기간 저장되는 탄소를 의미한다. 현재 기후변화에 관한 정부 간 협의체(IPCC, Intergovernmental Panel on Climate Change)에서 현재 공식적으로 인정하고 있는 블루카본 생태계는 맹그로브, 염습지, 해초지 3가지뿐이다. 하지만, 최근 해조류, 미세조류, 산호초, 비식생 갯벌 등 다양한 새로운 블루카본 흡수원들이 가진 높은 이산화탄소 격리 및 저장 능력에 대해 새로운 연구 결과들이 지속적으로 학계에 보고되고 있어, 이들 신규 블루카본 후보군들의 온실가스 흡수량 산정에 관련된 과학적 입증을 통해 IPCC 국제 인증의 가능성이 점차 높아지고 있다. 본 총설에서 동해안이 보유하고 있는 블루카본 흡수원인 해조류, 해초지 및 비식생 갯벌의 현황과 잠재적 가치에 대해 논하고자 한다. 본 논문을 통해 동해는 해조류 자원을 NbS로 활용하는 것이 가장 효과적인 것으로 확인되었다. 또한, 동해안이 보유한 신규 블루카본 흡수원이 이른 시일 내에 IPCC 국제 인증을 받을 수 있도록 연구개발의 방향성과 활용방안을 제안하고자 한다.

• 전자공학회논문지D
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• 제35D권11호
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• pp.55-61
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• 1998

정공 전달 중합체인 Poly(N-vinylcarbazole) (PVK)와 전자전달 유기물 재료인 2-(4-biphenyl)-5-(t-butyl-phenyl)-1,3,4-oxadiazole (Bu-PBD)에 발광 유기물 색소 Coumurine 6, TPB, Rhodamine B를 각각 도핑한 단층박막 유기물 전기발광 소자를 제작하였다. 스핀 코팅 방법에 의한 단층 구조와 가용성 재료의 사용으로부터 소자제작이 간단하였다. 활성영역은 인듐주석산화물(ITO) 과 알루미늄 전극 사이에 놓인 단층으로 구성하고 있다. 이러한 구조에서 전자와 정공의 전하가 각 전극에서 PVK : Bu-PBD 활성층으로 주입된다. 전압을 인가한 후 발광된 빛의 색은 각각 TPB, C6, Rhodamine B의 유기물 색소에 의해 481nm, 500nm, 585nm 파장을 갖는 푸른색, 초록색 및 오렌지색을 나타내었다. PVK유기물은 다른 발광색을 갖는 유기물 색소를 분자 적으로 도핑 함으로서 주요한 중합체로서 사용될 수 있다. 그리고 전기발광색은 전체 가시광선 파장 내로 조절될 수 있다.

• 한국전기전자재료학회논문지
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• 제30권3호
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• pp.192-197
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• 2017

Hydrogenated Amorphous Silicon (a-Si:H) is used as an emitter layer in HIT (heterojunction with Intrinsic Thin layer) solar cells. Its low band gap and low optical properties (low transmittance and high absorption) cause parasitic absorption on the front side of a solar cell that significantly reduces the solar cell blue response. To overcome this, research on CSC (carrier Selective Contacts) is being actively carried out to reduce carrier recombination and improve carrier transportation as a means to approach the theoretical efficiency of silicon solar cells. Among CSC materials, molybdenum oxide ($MoO_x$) is most commonly used for the hole transport layer (HTL) of a solar cell due to its high work function and wide band gap. This paper analyzes the electrical and optical properties of $MoO_x$ thin films for use in the HTL of HIT solar cells. The optical properties of $MoO_x$ show better performance than a-Si:H and ${\mu}c-SiO_x:H$.

• 한국응용과학기술학회지
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• 제29권3호
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• pp.459-465
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• 2012

본 연구에서 7,7'-(2,2'dimethoxy-1,1'-binaphthyl-3,3'-diyl) bis(4-(thiophen-2-yl) benzo[e] [1,2,5] thiadiazole (TBT) 라는 binaphthyl기를 기반으로 가지는 녹색 도판트 물질을 합성하였다. 추가적으로 인광 발광 물질인 iridium(III)bis[(4,6-di-fluoropheny)-pyridinato -N,C2]picolinate (FIrpic)을 홀 수송용 호스트 물질인 N,N'-dicarbazolyl-3,5-benzene (mCP)에 도핑하고, TBT와 bis(2-phenylquinolinato)-acetylacetonate iridium(III) (Ir(pq)2acac)를 전자 수송용 호스트 물질인 1,3,5-tris(N-phenylbenzimidazole-2-yl)benzene (TPBi)에 도핑하여 백색 빛을 발광하는 white organic light emitting diode (OLED)를 제작하였다. TBT를 사용하여 제작한 white OLED의 최대발광 효율과 외부 양자 효율은 각각 5.94 cd/A 과 3.23%를 나타냄을 알 수 있었다. Commission Internationale de I'Eclairage (CIE) 색 좌표의 값은 1000 nit에서 (0.34, 0.36)을 띄면서 순백색을 구현함을 확인하였다.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 춘계학술발표대회
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• pp.11.2-11.2
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• 2011

Polymer based organic photovoltaics have attracted a great deal of attention due to the potential cost-effectiveness of light-weight and flexible solar cells. However, most BHJ polymer solar cells are not thermally stable as subsequent exposure to heat drives further development of the morphology towards a state of macrophase separation in the micrometer scale. Here we would like to show three different approaches for developing new electroactive polymers to improve the thermal stability of the BHJ solar cells, which is a critical problem for the commercialization of these solar cells. For one of the examples, we report a new series of functionalized polythiophene (PT-x) copolymers for use in solution processed organic photovoltaics (OPVs). PT-x copolymers were synthesized from two different monomers, where the ratio of the monomers was carefully controlled to achieve a UV photo-crosslinkable layer while leaving the ${\pi}-{\pi}$ stacking feature of conjugated polymers unchanged. The crosslinking stabilizes PT-x/PCBM blend morphology preventing the macro phase separation between two components, which lead to OPVs with remarkably enhanced thermal stability. The drastic improvement in thermal stabilities is further characterized by microscopy as well as grazing incidence X-ray scattering (GIXS). In the second part of talk, we will discuss the use of block copolymers as active materials for WOLEDs in which phosphorescent emitter isolation can be achieved. We have exploited the use of triarylamine (TPA) oxadiazole (OXA) diblock copolymers (TPA-b-OXA), which have been used as host materials due to their high triplet energy and charge-transport properties enabling a balance of holes and electrons. Organization of phosphorescent domains in TPA-b-OXA block copolymers is demonstrated to yield dual emission for white electroluminescence. Our approach minimizes energy transfer between two colored species by site isolation through morphology control, allowing higher loading concentration of red emitters with improved device performance. Furthermore, by varying the molecular weight of TPA-b-OXA and the ratio of blue to red emitters, we have investigated the effect of domain spacing on the electroluminescence spectrum and device performance.

• 분석과학
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• 제34권3호
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• pp.128-133
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• 2021

적정 화학반응에는 화학종의 전위차 변화뿐만 아니라 지시약의 색깔 변화도 포함된다. 전위차 적정에서는 종말점에서 전위의 급격한 변화를 측정하여 적정 곡선을 얻는다. 산-염기 적정은 일반적으로 지시약의 색 변화를 관찰하여 종말점을 결정함으로써 수행된다. 전위차를 측정하여 종말점을 결정하는 방법은 잘 확립 되어 상용화되어 있지만 색의 변화를 관찰하여 종말점을 얻는 장치는 많지 않은 실정이다. 적외선 광원과 감지기로 적정액 방울을 계수하고, 백색광원과 광 검출기로 종말점의 변색을 감지하여 아날로그-디지털 변환기인 아두이노 (Arduino)가 적용된 간단하고 정밀한 스펙트럼 종말점 검출 기구를 제작하였다. Spectrator는 지시약으로 티몰 블루를 사용한 산-염기 적정에서 재현성 측면에서 우수한 결과를 보였다. Spectrator 제작 과정과 이를 사용한 실험결과를 공유한다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.293-293
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• 2014

Over last decade InGaN alloy structures have become the one of the most promising materials among the numerous compound semiconductors for high efficiency light sources because of their direct band-gap and a wide spectral region (ultraviolet to infrared). The primary cause for the high quantum efficiency of the InGaN alloy in spite of high threading dislocation density caused by lattice misfit between GaN and sapphire substrate and severe built-in electric field of a few MV/cm due to the spontaneous and piezoelectric polarizations is generally known as the strong exciton localization trapped by lattice-parameter-scale In-N clusters in the random InGaN alloy. Nonetheless, violet-emitting (390 nm) conventional low-In-content InGaN/GaN multi-quantum wells (MQWs) show the degradation in internal quantum efficiency compared to blue-emitting (450 nm) MQWs owing higher In-content due to the less localization of carrier and the smaller band offset. We expected that an improvement of internal quantum efficiency in the violet region can be achieved by replacing the conventional low-In-content InGaN/GaN MQWs with ultra-thin, high-In-content (UTHI) InGaN/GaN MQWs because of better localization of carriers and smaller quantum-confined Stark effect (QCSE). We successfully obtain the UTHI InGaN/GaN MQWs grown via employing the GI technique by using the metal-organic chemical vapor deposition. In this work, 1 the optical and structural properties of the violet-light-emitting UTHI InGaN/GaN MQWs grown by employing the GI technique in comparison with conventional low-In-content InGaN/GaN MQWs were investigated. Stronger localization of carriers and smaller QCSE were observed in UTHI MQWs as a result of enlarged potential fluctuation and thinner QW thickness compared to those in conventional low-In-content MQWs. We hope that these strong carrier localization and reduced QCSE can turn the UTHI InGaN/GaN MQWs into an attractive candidate for high efficient violet emitter. Detailed structural and optical characteristics of UTHI InGaN/GaN MQWs compared to the conventional InGaN/GaN MQWs will be given.

• E2M - 전기 전자와 첨단 소재
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• 제12권7호
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• pp.7-11
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• 1999

Fully sealed field emission display in size of 4.5 inch has been fabricated using single-wall carbon nanotubes-organic vehicle com-posite. The fabricated display were fully scalable at low temperature below 415$^{\circ}C$ and CNTs were vertically aligned using paste squeeze and surface rubbing techniques. The turn-on fields of 1V/${\mu}{\textrm}{m}$ and field emis-sion current of 1.5mA at 3V/${\mu}{\textrm}{m}$ (J=90${\mu}{\textrm}{m}$/$\textrm{cm}^2$)were observed. Brightness of 1800cd/$m^2$ at 3.7V/${\mu}{\textrm}{m}$ was observed on the entire area of 4.5-inch panel from the green phosphor-ITO glass. The fluctuation of the current was found to be about 7% over a 4.5-inch cath-ode area. This reliable result enables us to produce large area full-color flat panel dis-play in the near future. Carbon nanotubes (CNTs) have attracted much attention because of their unique elec-trical properties and their potential applica-tions [1, 2]. Large aspect ratio of CNTs together with high chemical stability. ther-mal conductivity, and high mechanical strength are advantageous for applications to the field emitter [3]. Several results have been reported on the field emissions from multi-walled nanotubes (MWNTs) and single-walled nanotubes (SWNTs) grown from arc discharge [4, 5]. De Heer et al. have reported the field emission from nan-otubes aligned by the suspension-filtering method. This approach is too difficult to be fully adopted in integration process. Recently, there have been efforts to make applications to field emission devices using nanotubes. Saito et al. demonstrated a car-bon nanotube-based lamp, which was oper-ated at high voltage (10KV) [8]. Aproto-type diode structure was tested by the size of 100mm $\times$ 10mm in vacuum chamber [9]. the difficulties arise from the arrangement of vertically aligned nanotubes after the growth. Recently vertically aligned carbon nanotubes have been synthesized using plasma-enhanced chemical vapor deposition(CVD) [6, 7]. Yet, control of a large area synthesis is still not easily accessible with such approaches. Here we report integra-tion processes of fully sealed 4.5-inch CNT-field emission displays (FEDs). Low turn-on voltage with high brightness, and stabili-ty clearly demonstrate the potential applica-bility of carbon nanotubes to full color dis-plays in near future. For flat panel display in a large area, car-bon nanotubes-based field emitters were fabricated by using nanotubes-organic vehi-cles. The purified SWNTs, which were syn-thesized by dc arc discharge, were dispersed in iso propyl alcohol, and then mixed with on organic binder. The paste of well-dis-persed carbon nanotubes was squeezed onto the metal-patterned sodalime glass throuhg the metal mesh of 20${\mu}{\textrm}{m}$ in size and subse-quently heat-treated in order to remove the organic binder. The insulating spacers in thickness of 200${\mu}{\textrm}{m}$ are inserted between the lower and upper glasses. The Y\ulcornerO\ulcornerS:Eu, ZnS:Cu, Al, and ZnS:Ag, Cl, phosphors are electrically deposited on the upper glass for red, green, and blue colors, respectively. The typical sizes of each phosphor are 2~3 micron. The assembled structure was sealed in an atmosphere of highly purified Ar gas by means of a glass frit. The display plate was evacuated down to the pressure level of 1$\times$10\ulcorner Torr. Three non-evaporable getters of Ti-Zr-V-Fe were activated during the final heat-exhausting procedure. Finally, the active area of 4.5-inch panel with fully sealed carbon nanotubes was pro-duced. Emission currents were character-ized by the DC-mode and pulse-modulating mode at the voltage up to 800 volts. The brightness of field emission was measured by the Luminance calorimeter (BM-7, Topcon).