반도체 나노입자의 형상제어 및 광전자소자로의 응용

학위논문 (박사)-- 서울대학교 대학원 : 화학생물공학부, 2013. 2. 차국헌.Shape- and size-controlled semiconductor nanocrystals have recently drawn keen attention due to their tunable optical and electrical properties. Precise control in their dimension and spatial chemical composition (i.e., dot, rod, or tetrapod structure with homogeneous or multi-compositions) enables us to manipulate their electronic states, exciton generation/relaxation dynamics, and transport phenomena, which determines light absorption, fluorescence, or carrier transport within nanocrystals or nanocrystals arrays. In order to realize their full potentials to practical applications based on these promising materials, deeper understanding on their physical and chemical properties as well as systematic utilization should be progressed. In these regards, design principles on semiconductor nanocrystals to control optical or electrical properties and their applications to optoelectronic devices are discussed. For effective generation of photons from other energy sources, spherical-shaped InP quantum dots with ZnSeS chemical composition gradient are synthesized by wet chemistry. The composition gradient of Se in the shell phase is easily achieved by one-pot approach with a simple addition of both Se and S precursors at the same time, where Se is dominantly located close to the InP cores while S content increases along the radial direction of the shell. The introduction of the ZnSeS composition gradient shells ensures high quantum efficiency above 70 % due to the successful passivation of surface states with reduced lattice strain and also improves chemical stability against chemical and physical stress. In order to facilitate the exciton dissociation for photovoltaic devices, tetrapod-shaped cadmium selenide nanocrystals are synthesized by continuous precursor injection approach. The continuous precursor injection implies the successive injection of precursor solution and branching agent using a syringe pump with a controlled injection rate. The CdSe tetrapods prepared with new synthetic route exhibit exceptional shape selectivity above 90 % as well as finely tunable dimensions varying from 1 to above 40 in aspect ratio simply by controlling the reaction temperature and injection rate. Moreover, these high quality tetrapods can be easily scaled-up in multi-gram quantity without reduction in morphological uniformity. Using the InP quantum dots with ZnSeS chemical composition gradient shells, highly efficient and bright green light emitting diodes are demonstrated. On the basis of an inverted device structure, solution-processed interfacial dipole was introduced for minimizing electron injection barrier between an electron transport layer to InP quantum dots. Optimized carrier transport energy levels allows direct injection of charge carriers within quantum dots, which leads to the considerable improvement in external quantum efficiency of the devices in entire operation range. To utilize CdSe tetrapods in organic-inorganic hybrid solar cells in reproducible and reliable manner, sequential fabrication is employed to realize bicontinuous hybrid morphology. The sequential fabrication solves the poor colloidal stability of ligand-less tetrapods as well as the inseparable fabrication variables participating in nanoscopic morphology and surface state of nanocrystals. It is found that primary amines could effectively passivate surface state of CdSe nanocrystal phase and contribute to the enhancement of device performance. The improved device performance is rationalized by the reduced bimolecular recombination of charged carriers at the trap sties. The optimized device shows considerable power conversion efficiency up to 2.2 % with high reproducibility. This thesis demonstrates the practical approaches to exploit semiconductor nanocrystals into the practical devices, covering the tailored synthesis of nanocrystals, suitable device structure, and novel processing method. It is believed that this comprehensive approach will make a success on the realization of emerging nanoscience into the practical optoelectronic applications.Chapter 1 Introduction 1 1.1 Fundamental properties of semiconductor nanocrystals 1 1.2 Design principle of semiconductor nanocrystals for optoelectronic devices 10 1.3 Applications of shape-controlled semiconductor nanocrystals 23 1.3.1 Quantum dot-based light emitting diodes (QD-LEDs) 23 1.3.2 Semiconductor nanocrystal-based photovoltaic devices 29 1.3.3 Water splitting systems 32 Chapter 2 Synthesis of Shape-Controlled Semiconductor Nanocrystals for Photon-Electron Conversion Materials 34 2.1 InP@ZnSeS, core@composition gradient shell quantum dots for efficient lumophors 34 2.1.1 Introduction 34 2.1.2 Experimental section 37 2.1.3 Results and Discussions 40 2.1.4 Conclusions 55 2.2 Scalable and Controllable Synthesis of CdSe Tetrapods with High Morphological Uniformity by Persistent Kinetic Growth and Halide-Mediated Phase Transformation 56 2.2.1 Introduction 56 2.2.2 Experimental section 59 2.2.3 Results and Discussions 64 2.2.4 Conclusions 82 Chapter 3 Fabrication of InP Quantum Dot-Based Light Emitting Diodes 83 3.1 Introduction 83 3.2 Experimental section 86 3.3 Results and Discussions 89 3.4 Conclusions 101 Chapter 4 Stepwise Formation of CdSe Tetrapod:P3HT Bulkheterojunction for Hybrid Solar Cells 102 4.1 Introduction 102 4.2 Experimental section 106 4.3 Results and Discussions 112 4.4 Conclusions 132 Chapter 5 Conclusion and Outlook 133 Bibliography 142 Abstract 158Docto

形式的 當事者 訴訟에 關한 考察

학위논문(석사)--서울대학교 대학원 :법학과 행정법전공,2001.Maste

Development of an Advanced Rotorcraft Preliminary Design Framework

학위논문(석사) --서울대학교 대학원 :기계항공공학부,2010.2.Maste

Lift offset 복합형 회전익기의 로터 구조 최적설계 프레임워크 개발 연구

학위논문 (박사)-- 서울대학교 대학원 : 기계항공공학부, 2014. 8. 신상준.Design optimization for the structural construction of a rotor system in a compound rotorcraft with a lift offset was conducted by applying a two-level procedure. In this optimization process, enhancements were made regarding the high-speed forward flight capability, vibration characteristics, and rotor blade weight of a compound rotorcraft. In this type of rotorcraft, the combination of a lift offset, a rigid rotor blade, and a variable rotor speed enables the achievement of satisfactory vibration characteristics and high forward speed performance. Optimized structural properties of the blade and chordwise geometries for each blade radial station were obtained by the present upper-level optimization scheme. By applying the proposed lower-level optimization scheme, an optimized cross-sectional configuration of a composite rotor blade was determined. For validation purposes, the design of an existing stiff-in-plane rotor in XH-59A compound rotorcraft was optimized by applying the present procedure. As a result, it was found that most of the objective function values were significantly improved. The influence of the optimization results on the conceptual design was evaluated. It is expected that the present procedure will be applicable for the next-phase advanced compound rotorcraft, which will target further high forward speed capability with low vibration characteristics.본 논문에서는 Lift offset 로터와 보조추진장치가 장착된 복합형 회전익기의 로터 최적설계 프레임워크를 2 단계의 형태로 개발하였다. 개발된 최적화 프레임워크에 의해 고속전진비행에서의 복합형 회전익기의 성능, 진동, 중량이 향상되었다. lift offset 복합형 회전익기는 lift offset, 강성이 높은 로터 블레이드, 로터 회전속도 변화 등의 다양한 요소가 진동과 성능에 미치기 영향 때문에, 진동과 성능 모두를 만족시키는 설계를 도출하는 것이 난이하다. 상위 최적설계에서는 로터 블레이드의 최적화된 물성치와 시위길이가 도출된다. 상위 최적설계 프레임워크에서 도출된 시위길이, 질량 및 강성 값을 가지는 복합재 블레이드 단면의 설계가 하위 최적설계에서 수행되었다. XH-59A 복합형 회전익기의 자료를 이용하여 개발된 최적설계 프레임워크를 이용한 최적설계를 수행하였다. 그 결과 대부분의 목적함수가 상당히 향상되었음을 확인하였다. 로터 최적설계 결과가 회전익기 개념설계 결과에 미치는 영향을 알아보기 위해 lift offset 복합형 회전익기의 개념설계가 수행 가능한 개념설계 프레임워크가 개발되었다. 이를 이용하여 로터 최적설계 결과가 개념설계에 미치는 영향을 확인하여 본 결과 향상된 로터 성능 및 중량으로 인해 총 중량이 감소한 회전익기가 설계됨을 확인하였다.Abstract Contents List of Tables List of Figures Chapter 1 Introduction 1.1 Background and Motivation 1.2 Previous Researches 1.2.1 Previous Researches on Rotor Design Optimization 1.2.2 Previous Researches on Development of a Conceptual Design Program for a Compound Rotorcraft 1.3 Objectives and Thesis Overview Chapter 2 Rotor Design Optimization Framework for a Lift Offset Compound Aircraft 2.1 Upper-Level Optimization 2.2 Lower-Level Optimization Chapter 3 Improvement Strategy on HCDO Program to Include a Design Capability for a Compound Rotorcraft with a Lift Offset 3.1 Improvement on the Power Required Estimation Algorithm 3.2 Improvement on the Estimation of Flat Plate Drag Area Chapter 4 Design Optimization Results 4.1 Validation of CAMRAD II Input 4.2 Parametric Study of the Lift Offset 4.3 Sensitivity Test to select Design Variables 4.4 Development of an Approximate Model using RSM 4.5 Upper-Level Optimization 4.6 Lower-Level Optimization Chapter 5 Influence of the Optimization Results on the Conceptual Design 5.1 Development of Rotor Map 5.2 Influence Verification of the Optimization Results on the Conceptual Design Chapter 6 Conclusions References Appendix A. Helicopter Conceptual Design and Optimization Framework Abstract (Korean)Docto

A Study on Plato`s philosophy of mathematics education

학위논문(박사)--서울대학교 대학원 :수학교육과,1998.Docto

단기 메모리 접근 정보를 이용한 동적 전압 주파수 변환 기법의 개선

학위논문(석사) --서울대학교 대학원 :전기. 컴퓨터공학부,2008.2.Maste

An Analysis of the Effects of the Cultural Voucher Policy on Cultural Expenditure

문화바우처는 2005년도부터 문화향유를 통한 삶의 질 개선, 문화격차 해소라는 목표를 달성 하기 위해 도입되었다. 그러나 문화바우처에 대한 연구는 문화향유를 통한 삶의 질 개선과 관련된 연구에 편향되어 있으며, 문화격차 해소와 관련된 연구는 미흡한 실정이다. 이에 본 연구에서는 문화격차와 관련한 문화바우처 제도의 변동 효과를 분석하였다. 일반적으로 문화격차는 문화접근도와 문화이용도로 구분되어 설명되는데, 본 연구에서는 문화이용도의 측면에 한정하여, 문화지출비의 변동을 분석하였다. 문화지출비는 한국조세재정연구 원의 재정패널조사자료를 활용했다. 문화바우처 정책 변동의 효과는 크게 통합문화이용권 도입사업의 실시 전후의 효과와 지원금 증액방식의 효과, 둘로 구분하여 분석하였다. 첫째, 통합문화이용권 도입사업 실시 이후, 문화지출비는 사업 이전보다 증가하는 것으로 분석되었다. 이는 문화체험기회 확대 방식이 문화소비지출에 긍정적인 영향을 주었음을 시사한다. 둘째, 지원금 확대 시행은 문화지출비 변동에 유의한 영향을 미치지 않는 것으로 분석되었다. 본 연구의 분석결과는, 가구의 문화지출비를 증액시키기 위해서는 지원금 증액방식보다 문화 체험기회의 확대방식이 효과적임을 시사한다

Composition for surface modification of nano particle, Method for manufacturing composition for surface modification of nano particle, Method for surface modification of nano particle, Method for manufacturing surface modified nano particles and Surface modified nano particles

본 발명의 일실시예는 나노입자 표면개질용 조성물, 나노입자 표면개질용 조성물 제조방법, 나노입자 표면개질 방법, 표면개질된 나노입자 제조방법 및 표면개질된 나노입자를 제공한다. 상세하게는 나노입자 표면개질용 복합체를 활용하여 양자 효율(quantum yield; QY)을 보존할 수 있을 뿐만 아니라 장기 안정성을 크게 향상시킨 나노입자 표면개질용 조성물, 나노입자 표면개질용 조성물 제조방법, 나노입자 표면개질 방법, 표면개질된 나노입자 제조방법 및 표면개질된 나노입자를 제공한다