http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Gap state formation by interfacial interaction between Al and 8-hydroxyquinolatolithium
Yi, Yeonjin,Lee, Young Mi,Park, Yongsup,Kim, Jeong Won Royal Society of Chemistry 2010 Physical chemistry chemical physics Vol.12 No.32
<P>The interfacial interaction between hydroxyquinolatolithium (Liq) and Al was studied with <I>in situ</I> synchrotron radiation photoemission (SRP) and density functional theory (DFT) calculation. The metal Al was deposited on pristine Liq molecular layer in a stepwise manner and the SRP measurements were conducted before and after each deposition step. The SRP results were analyzed by DFT calculation using a simple model and the key interaction between them was explained: Liq is not broken to generate free Li<SUP>+</SUP> ions upon Al interaction, unlike the reaction of its inorganic counterpart Al–LiF–Alq<SUB>3</SUB>, but rather makes a Liq–Al complex with charge donation from Al to Liq. Electrons from Al fill the LUMO level of Liq and generate a new gap state. The charge control properties of the Liq layer could be explained with this gap state in terms of the intermediate-state assisted carrier transport.</P> <P>Graphic Abstract</P><P>New filled state is formed in the original gap of Liq by electron donation from Al to the LUMO of Liq. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c000282h'> </P>
Yi, Yeonjin,Choi, Won Mook,Son, Byoungchul,Kim, Jeong Won,Kang, Seong Jun Elsevier 2011 Carbon Vol.49 No.14
<P><B>Abstract</B></P><P>The interfacial electronic structure of fullerene (C<SUB>60</SUB>) deposited on a multilayer graphene (MLG) film was measured using <I>in situ</I> ultraviolet photoelectron spectroscopy and X-ray photoelectron spectroscopy. The energy level alignment at the interface of C<SUB>60</SUB>/MLG was estimated by the shifts in the highest occupied molecular orbital (HOMO) and the vacuum level during step-by-step deposition of C<SUB>60</SUB> on the MLG. The shift of the HOMO level indicates that there is a small band bending at the interface of C<SUB>60</SUB>/MLG. The vacuum level was shifted 0.06eV toward the low binding energy with additional C<SUB>60</SUB> on the MLG. The measurements reveal that the height of the electron injection barrier is 0.59eV, while the hole injection barrier height is 2.01eV. We present a complete interfacial energy level diagram for C<SUB>60</SUB>/MLG.</P>
In situ 광전자분광/역광전자분광 분석을 이용한 유기물 계면의 전자구조 연구
이연진,Yi, Yeonjin 한국진공학회 2015 진공 이야기 Vol.2 No.2
본 글에서는 광전자 분광 및 역광전자 분광을 이용한 유기분자 시스템의 전자구조 연구에 대하여 기술하였다. 다양한 유기물간의 계면 연구가 급속도로 늘어나고 있으며, 폴리머, 거대 분자 등 기존의 in situ 분석 방법으로 실험이 어려운 물질까지도 연구의 필요성이 늘어나고 있다. Electrospray 증착 방법이 이러한 새로운 물질들의 계면 전자구조 연구를 가능하게 할 수 있음을 살펴보았으며, 다양한 새로운 분석 기법들의 출현을 기대해 본다. 몇 가지 예에서 살펴본 바와 같이 전자구조는 소자 구동 특성을 직접적으로 지배하는 핵심적인 물리량이며, 전자구조의 이해를 통해 전자소자의 구동 원리, 성능 최적화 및 소자 특성 열화의 원인을 파악할 수 있다. 현재, 유기물 소자 관련 기술의 성숙도는 전자구조 분석과 같은 기초 연구 결과 없이는 더 이상 발전할 수 없는 정도에 이르러, 관련 분석 기술에 대한 수요가 더욱 늘어날 것으로 전망된다. During last two decades, remarkable progresses have been made in organic electronic devices, such as organic light-emitting device, organic photovoltaic and many other applied devices. Many of these progress are attributed to the multilayered/heterojunction device architectures, which could be achieved from the control of "interfacial energetics". In that sense, the interfacial electronic structures in organic electronic devices have a decisive role in device performance. However, the prediction of the interfacial electronic structures from each separate material is not trivial. Many complex phenomena occur at the interface and these can be only understood from thorough measurements on interfacial electronic structures in situ. Photoemission and inverse photoemission spectroscopy have been known as the most proper measurement tools to analyze these interfacial electronic structures. In this review, the basic principles of (inverse) photoemission spectroscopy and typical measurement results on organic/inorganic interfaces are introduced.
Hole injection improvement using ultrathin Li-TFSI layer in organic light-emitting diodes
Kim Kiwoong,Yi Yeonjin,Lee Hyunbok 한국물리학회 2021 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.79 No.10
A high device performance of organic light-emitting diodes (OLEDs) can be achieved by minimizing the hole injection barrier (HIB) at the anode interface. However, the work function of indium tin oxide (ITO) is not sufficiently high; thus, the use of an appropriate hole injection layer (HIL) is necessary. In this study, we demonstrated that bis(trifluoromethane) sulfonimide lithium salt (Li-TFSI) is an efficient HIL to decrease the HIB in OLEDs. The device performances of hole-only devices (HODs) and OLEDs were significantly enhanced by the insertion of the ultrathin Li-TFSI HIL between the N,N′- di(1-naphthyl)-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine (NPB) hole transport layer and ITO. In situ ultraviolet photoelectron spectroscopy measurements revealed that the work function of ITO was considerably increased by the deposition of the Li-TFSI HIL. Accordingly, the HIB from ITO to NPB was remarkably reduced. This is the origin of the hole injection improvements in the HODs and OLEDs with the Li-TFSI HIL. Thus, Li-TFSI would be an efficient interface modifier to increase the work function of the electrode and decrease the HIB in various electronic devices.
Kang Donghee,Yi Yeonjin,Lee Hyunbok 한국물리학회 2021 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.78 No.9
To obtain efficient organic light-emitting diodes (OLEDs), the degradation in the surface properties of the indium tin oxide (ITO) electrode during the device fabrication should be prevented. In this study, we investigated the effect of the waiting time of ITO in the entry chamber before the transfer to the deposition chamber on the device performances of OLEDs. The current density and luminance of the OLED significantly decreased owing to the reduced hole injection with the increase in the waiting time. The origin of the reduced hole injection was estimated to be (1) the formation of trap sites at the interface between ITO and hole-transport layer and (2) decreased work function of ITO by an interface dipole. These phenomena could be attributed to the contamination of the ITO surface by the waiting under a relatively low vacuum and room light illumination.
Kim Kiwoong,Yi Yeonjin,Han Daeyeop,Choi Jinchul 한국물리학회 2021 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.79 No.9
The effect of the substrate temperature during the deposition of a ZnO:Al (AZO) window layer on the performance of Cu(In, Ga)Se2 (CIGS) solar cells was studied. Although the structural, electrical and optical properties of separate AZO films are enhanced with higher substrate temperature, the overall performance of final CIGS solar cells is deteriorated. At higher substrate temperature, the diffusion of Cd, Zn and Al into the CIGS absorber layer was observed with secondary ion-mass spectroscopy measurements. This diffusion could form a buried p–n junction, resulting in deteriorated device characteristics.