Organic Lasing: Correlation between Molecular Structure, Optical and Optoelectronic Properties

학위논문 (박사)-- 서울대학교 대학원 : 화학과, 2013. 2. Frédéric Laquai.In this thesis mainly two alternating indenofluorene-phenanthrene copolymers were investigated with a variety of spectroscopic and optoelectronic experiments. The different experimental techniques allowed to retrieve deeper insights into their unique optical as well as optoelectronic properties. The motivation of the research presented in this work was to correlate their photophysical properties with respect to their application in electrically pumped lasing. This thesis begins with the description of optical properties studied by classical absorption and emission spectroscopy and successively describes an overall picture regarding their excited state dynamics occurring after photoexcitation studied by time-resolved spectroscopy. The different spectroscopic methods do not only allow to elucidate the different optical transitions occurring in this class of materials, but also contribute to a better understanding of exciton dynamics and exciton interaction with respect to the molecular structure as well as aggregation and photooxidation of the polymers. Furthermore, the stimulated emission properties were analyzed by amplified spontaneous emission (ASE) experiments. Especially one of the investigated materials, called BLUE-1, showed outstanding optical properties including a high optical gain, a low threshold for ASE and low optical losses. Apart from the optical experiments, the charge carrier mobility was measured with the time-of-flight technique and a comparably high hole mobility on the order of 1 x 10² cm²/(Vs) was determined for BLUE-1 which makes this material promising for organic lasing. The impact of the high charge carrier mobility in this material class was further analyzed in different optoelectronic devices such as organic LEDs (OLEDs) and organic solar cells.1 introduction 1 2 theoretical basics 5 2.1 Absorption and Emission of Light 5 2.2 Electronic configuration of carbon atoms in molecules 7 2.3 Optical Properties of Organic Molecules 8 2.3.1 Optical transitions in organic molecules 8 2.3.2 Absorption of light in organic molecules 10 2.3.3 Spectral lineshapes in organic molecules 13 2.3.4 Photoluminescence quantum efficiency 14 2.3.5 Intermolecular interactions of molecules 15 2.4 The Gaussian Disorder Model 17 2.5 Lasing in Organic Semiconductors 21 2.6 Organic light emitting diodes 22 3 optical spectroscopy 25 3.1 The class of poly(indenofluorenes) 25 3.1.1 Introduction 25 3.2 Experimental 26 3.2.1 Sample preparation 26 3.2.2 Steady-state spectroscopy 27 3.2.3 Time-resolved spectroscopy 27 3.2.4 Amplified spontaneous emission and lasing 30 3.3 Absorption and emission spectroscopy 32 3.3.1 Quasi steady-state excited state absorption 33 3.4 Time-resolved fluorescence spectroscopy on BLUE-1 and BLUE-2 34 3.4.1 Fluorescence spectroscopy 34 3.4.2 Defect emission 39 3.4.3 The origin of non-monoexponential dynamics in BLUE-1 42 3.4.4 Delayed fluorescence of BLUE-1 47 3.5 Amplified spontaneous emission and lasing 51 3.5.1 Introduction 51 3.5.2 Results and discussion on PIF, BLUE-1 and BLUE-2 53 3.5.3 Lasing characteristics 60 3.5.4 ASE from a PIF-triphenylamine copolymer 63 3.6 Transient absorption spectroscopy on BLUE-1 72 3.7 Summary and conclusions of chapter 3 76 4 the influence of high mobilities in optoelectronic devices 79 4.1 Introduction 79 4.2 Experimental 80 4.2.1 Time-of-flight technique 80 4.2.2 OLED preparation 80 4.2.3 OLED characterization 81 4.2.4 Organic solar cell preparation and characterization 82 4.3 The time-of-flight technique 82 4.4 OLED characterization of different PIF-based copolymers 86 4.4.1 Introduction 86 4.4.2 OLED characteristics of BLUE-1 87 4.4.3 OLED characteristics of BLUE-2 91 4.4.4 Multilayer OLEDs- the impact of hole injection layers 93 4.5 Consequences of results on BLUE-1 for future lasing diodes 98 4.6 Exciton dissociation in a wide bandgap polymer 100 4.6.1 Introduction 100 4.6.2 Optical properties of BLUE-1 blended with PCBM 101 4.6.3 Solar cell performance of BLUE-1:PCBM blends 105 4.7 Summary and conclusions of chapter 4 107 5 conclusions and outlook 109 a appendix a 113 bibliography 123Docto

Atomistic origins of mechanical amorphization of SiO2 using solid-state 29Si NMR and local electronic structures for SiO2 high pressure phases using ab initio calculation

학위논문 (석사)-- 서울대학교 대학원 : 지구환경과학부, 2017. 2. 이성근.Silica (SiO2), the most abundant material on the earth, is a major component of the crust and mantle. Therefore the structure of silica affects the dynamic process of crust or the structural properties of the earth interior. The structure of silica changes not only by pressure-temperature change but also mechanical energy like friction without melting. To understand the properties of interior of rocky planets and the geological process, the detailed understanding of the structure of silica with various conditions is needed. In this study, we performed two major subject related to structure of silica. The first study is about atomistic origin of the mechanical amorphization of silica with an experimental methodology. There have been reported the reduction of fault strength during fault slip, and one of the causes is reported as the formation of the amorphous silica and the silica gel layer on the fault plane. The formation of amorphous silica is due to the frictional energy between the fault surfaces, and the formation of silica gel layer is due to reaction with the water present in the layer or air. In previous, studies on frictional experiments using quartzite rocks, reported the formation of silica and silica gel and also the decrease of friction coefficient, and the observation of the silica gel layer in natural faults has been reported. However, due to the complex structure of amorphous silica and the analytical method limitations, the atomic structure of the amorphized silica and the detailed origin of the mechanical amorphization process have not been clearly identified. In this study, silica was amorphized with mechanical energy by ball mill method, and the resulting amorphous structure was analyzed by high resolution nuclear magnetic resonance (NMR) spectroscopy. The morphology of the amorphized silica and the phases formed by other elements were analyzed using XRD, HR-TEM, and EDS-mapping method. Solid-state nuclear magnetic resonance spectroscopy (NMR) is suitable for the analysis of complex amorphous structures because it yields atomic environments in short range order around specific atoms and provides quantitative information on atomic unit bonding. The 29Si MAS NMR spectra of amorphous silica milled at different rates present that the spectra of samples milled above 600 rpm show a broad amorphous peak over -80 to -120 ppm. These amorphous peaks indicate the presence of Q2 and Q3 structures in the mechanically amorphized silica. The results indicate that the mechanical amorphization of silica occurs only above a certain energy level, and that the amorphization process results in a change in the short range atomic structure and imply the presence of reaction with other elements. This results help to understand the atomic structure of the mechanically amorphized silica and the mechanical amorphization process that occurs without melting in the fault plane. The second study is an electronic structure and detailed origin of spectral feature of O K-edge XRS for crystalline silica using computational computation. Crystalline silica undergoes various phase transition according to pressure-temperature change. Therefore, many studies on the structure of high-pressure phase silica have been reported to understand the internal structure of rocky planets in high temperature and high pressure environment. The most powerful method of in situ high-pressure study for electronic structure is O K-edge x-ray Raman spectroscopy (XRS) using diamond anvil cell and as experimental limitation above ~70 GPa, the computational methods is used to understand the XRS spectrum. However, the detailed relation between spectral feature of O K-edge XRS and structure is still in debate. In this study, we calculated electronic structures and O K-edge XRS spectra for various crystalline silica using ab initio calculation, and proved the origin of O K-edge XRS spectrum. Previous studies have suggested that the origin of the O K-edge XRS spectrum is attributed to the number of Si atoms or the number of O atoms. However, in this study, we have found that the O K-edge XRS spectra of hp-cristobalite with 4-coordination Si, of penta-SiO2 with 5-coordination Si and of stishovite with 6-coordination Si are similar, and O site resolved K-edge XRS spectra the penta-SiO2 revealed that the coordination of atoms does not directly affect the O K-edge XRS spectral feature. These results not only provide an understanding of the electronic structure of high-pressure phase silica, but also provide clear criteria for O K-edge XRS spectral analysis.1. INTRODUCTION 1 2. THEORETICAL BACGROUNDS 3 2.1 NMR TECHNIQUES 3 2.2 BALL MILL METHOD 4 2.3 AB INITIO CALCULATIONS 5 3. ATOMISTIC ORIGINS OF MECHANICAL AMORPHIZATION BY BALL MILL EXPERIMENTS: INSIGHTS FROM SI-29 NUCLEAR MAGNETIC RESONANCE 7 3.1. INTRODUCTION 7 3.2. EXPERIMENTS 9 3.2.1 Sample Preparation and Analysis 9 3.2.2 Planetary Ball Mill 9 3.2.3 NMR Spectroscopy 10 3.2.4 X-ray Diffraction 10 3.3. RESULTS AND DISCUSSION 11 3.3.1. TEM EDS 11 3.3.2. X-ray Diffraction Patterns 11 3.3.3. Si-29 MAS NMR 12 3.4. CONCLUSION 13 REFERENCE 14 4. AB INITIO CALCULATIONS OF LOCAL ELECTRONIC STRUCTURES AND X-RAY RAMAN SCATTERING SPECTRA FOR SIO2 HIGH PRESSURE PHASE 16 4.1 INTRODUCTION 16 4.2 AB INITIO CALCULATIONS 16 4.2.1 Crystal structures 16 4.2.2 Calculation conditions 19 4.2.3 PDOS and O K-edge XRS calculations 20 4.3 RESULTS AND DISCUSSION 21 4.3.1 O K-edge x-ray Raman scattering 21 4.3.2 Correlation between spectrum and crystal structure 22 4.4 CONCLUSION 23 REFERENCE 25 TABLES 29 FIGURE 30 APPENDIX SECTION 42 ABSTRACT IN KOREAN 44Maste

(A)Study on elemental reception and synthesis process in modern architecture of 1920~30 : focused on office buildings and governmental buildings

학위논문(석사)--서울대학교 대학원 :건축학과,2005.Maste

(A) Study on design changes and planning factors of high-rise office buidings in Korea since 1960's

학위논문 (박사)-- 서울대학교 대학원 : 건축학과, 2011.2. 심우갑.Docto

반추동물에 있어서 essential oil의 첨가가 항균작용, 생리작용 및 성장성적에 미치는 영향

Thesis (master`s)--서울대학교 대학원 :농생명공학부,2003.Essential oils are volatile oils obtained from plants by water distillation or steam distillation. Most essential oils consist of mixtures of hydrocarbons (terpenes etc.), oxygenated compounds (terpenoids etc.) and other components. Essential oils have potential against a wild range of microorganisms including bacteria, fungi, viruses, and protozoa. Some of components in essential oils have neurological effect, and structural similarity to gonadal steroid hormones and nature of the PPARγ ligands. It is suggested that essential oils may be substitute for antibiotic and potential regulation factors for some hormone secretions to control muscle and adipose development. So this study was conducted to observe these beneficial functions of essential oils in beef cattle.Maste

한국 자궁내막증 환자에서 alpha 2-Heremans-Schmidt glycoprotein (AHSG) 의 유전자다형성에 관한 연구

학위논문(석사)--서울대학교 대학원 :의학과 산부인과학전공,2004.Maste

도산위험과 기업가치 평가에 관한 연구

학위논문(석사)--서울대학교 대학원 :경영학과 경영학전공,1999.Maste

3D 프린팅을 위한 PETG/나노클레이 및 광경화수지/나노클레이 복합재료 제조 및 특성

학위논문 (박사) -- 서울대학교 대학원 : 농업생명과학대학 산림과학부(환경재료과학전공), 2021. 2. 김현중.The purpose of this study is to prepare a nanocomposite material by introducing a nanomaterial to a polymeric material, and apply it to 3D printing to a 3D structure having the functionality fabricate, and investigate the correlation between structural change and physical behavior. In this study, sepiolite clay was combined with polyethylene terephthalate glycol in a molten state using a twinextruder, and the resulting polymer nanocomposite was processed into a filament for extrusion molding of molten resin, applied to a 3D printing and traditional injection molding. As the proportion of sepiolite increased, mechanical properties of nanocomposite materials increased. The 3D printed material showed a higher reinforcing effect compared with the material from to injection molding. Through morphology observation using an electron microscopy and small-angle X-ray scattering, it was confirmed that sepiolite was oriented in the same direction as the 3D printing direction, and such orientation led to reinforcement of physical strength. In addition, computer simulation confirmed the orientation of material with the effective tensile strength. Montmorillonite, sepiolite, and halloysite clay were dispersed in a photocurable resin to prepare a photocurable nanoclay composite resin. The rheological, photo-curing behavior, and mechanical properties of the nanoclay-dispersed resin were investigated. Nanoclay affected the photocuring behavior of resin. Montmorillonite and sepiolite were more effective on improvement mechanical properties halloysite. The applicable amount and effective clay of in photocurable resins were established in 3D printing. Sepiolite showed the highest efficiency in mechanical and rheological properties for 3D printing and the nanoclay orientation of photocurable nanocomposite resin was studied. For 3D printing of low-concentration and low-viscosity of ink, the material was printed in a fumed silica/silicone oil slurry as a supporting matrix. The sepiolite compounded with the photocurable 3D printing material passed through the nozzle during direct ink printing. It was exposed to shearing force, and had orientation consistent with the printing direction. In addition, the tensile properties of the oriented sepiolite enhanced the mechanical properties of the printed composites more efficiently compared with the unoriented sepiolite. The composite of nanoclay to PETG and photocurable resin, improved mechanical properties of printed structures. The nano-oriented structure resulted from the rheological behavior of the material during the 3D printing process.본 연구의 목적은 고분자 3D 프린팅 재료에 나노 재료를 적용하여 나노 복합재료를 형성하고, 나노복합재료를 3D 프린팅에 적용하여 나노복합재료의 기능성을 가지는 3D 프린팅 물질을 제조하고 3D 프린팅 과정 중 재료의 구조 변화와 물리적 거동의 상관 관계를 규명하는데 있다. 폴리에틸렌 테레프탈레이트 글리콜에 세피올라이트 클레이를 트윈익스트루더를 사용하여 용융상태에서 복합화 하였으며 생성된 고분자 나노복합재료를 이용하여 용융수지 압출 조형용 필라멘트로 가공하여 3D 프린터에 적용하였으며 비교를 위하여 전통적인 사출성형에 또한 적용하였다. 고분자 나노복합재료를 각각 3D 프린팅 과 사출성형으로 인장강도 시편을 만들어 비교 기계적 인장강도를 비교하였다. 세피올라이트의 비율이 증가함에 따라 기계적 물성이 증가하였다. 3D 프린팅 된 재료의 인장강도 증가가 사출성형과 비교하여 함량대비 높은 보강효과를 보여주었다. 전자현미경을 이용한 모폴로지 관찰 및 소각엑스선산란법을 통하여 세피올라이트가 3D 프린팅 출력방향과 동일한 방향으로 배향되는 것을 확인하였으며 이러한 배향성의 발현이 효과적인 물리적 강도 보강 효과를 이끌어 내는 것을 확인하였다. 또한 컴퓨터 시뮬레이션을 통하여 배향된 재료가 효율적인 인장강도 향상과 관계가 있음을 확인하였다. 몬모릴로나이트, 세피올라이트, 할로이사이트 클레이를 광경화 수지에 분산하여 광경화 나노클레이 복합수지를 제조하였다. 나노클레이가 분산된 레진의 유변학적, 광경화 거동 및 기계적 물성 변화에 대하여 고찰하였다. 나노클레이는 레진의 광경화 거동에 영향을 미치며 몬모릴로나이트와 세피올라이트가 할로이사이트에 비하여 기계적 물성향상에 효과적인 것으로 확인 되었다. 나노클레이를 광경화 레진에 첨가하였을 경우 UV를 사용하는 3D 프린팅에 적용이 가능한 범위와 유효한 클레이에 대하여 정립하였다. 본 연구에서는 가장 높은 효율을 보여준 세피올라이트를 광경화형 3D 프린팅에 적용함과 동시에 광경화 나노복합수지의 나노클레이 배향성에 대하여 연구를 진행하였다. 세피올라이트의 광경화 수지와의 복합화 연구에서 얻어진 결과를 토대로 3D 프린팅 잉크의 직접 잉크 인쇄를 진행하였다. 기존 연구에서 구현할 수 없던 저농도, 저점도의 잉크의 3D 프린팅을 흄드 실리카/실리콘 오일 슬러리를 지지체로 사용하여 재료를 출력하였다. 광경화 3D 프린팅 재료와 복합화 된 세피올라이트는 직접 잉크 인쇄 중 노즐을 통과하며 전단력에 노출되고 프린팅 방향과 일치하는 배향성을 가지게 되는 것을 재료의 인장 파단면의 미세관찰을 통하여 확인하였다. 또한 배향된 세피올라이트는 재료의 기계적 인장특성 보강효과는 배향되지 않은 세피올라이트의 인장특성 보강효과와 비교하여 더욱 효율적으로 강화되는 것을 확인 하였다. 나노클레이를 PETG와 광경화 수지에 적용하여 3D 프린팅을 진행하였으며 기계적 특성이 향상된 고분자 나노복합재료를 출력하였으며, 3D 프린팅 과정 중 재료의 유변학적 거동에 의한 나노배향 구조를 확인할 수 있었다. 이를 통하여 기능성이 부여된3D 프린팅 재료를 재조하며 산업적 응용 범위를 확대해 나갈 수 있을 것으로 예상한다.Chapter 1 Introduction 1 1. Literature review 7 1.1 3D printing 7 1.2 Fused deposition modelling (FDM) 12 1.3 UV-assisted 3D printing 16 1.4 Direct Ink Write (DIW) 20 1.5 Matrix-assisted 3D printing (MAP) 22 1.6 3D printing materials 24 1.7 FDM 3D printing with polymer composite material 26 1.8 Effects of fillers constituting polymer and photo-curable resin composites on rheological properties 28 1.9 Nano orientation of 3D printed materials 29 3. Objectives 31 3.1. 3D printing of PETG/sepiolite composites with nano orientation 31 3.2. Behavior and properties of UV curable polymer nanocomposites based on inorganic nanofillers for 3D printing 33 3.3. Embedded DIW 3D printing of UV curable resin/sepiolite composites with nano orientation 34 Chapter 2 3D printing of PETG/sepiolite composites with nano orientation 37 1. Introduction 38 2. Experimental 41 2.1. Materials 41 2.2 Preparation of PETG/sepiolite nanocomposite 44 2.3 Preparation of filaments for FDM 3D printing 46 2.4 Preparation of specimens 48 2.5 Characterizations 52 2.5.1. tensile test 52 2.5.2. Small-angle X-ray scattering (SAXS) 52 2.5.3. Transmission electron microscopy (TEM) 54 2.5.4. Scanning electron microscope (SEM) 54 2.5.5. Rheometer 54 2.5.6. Dynamic mechanical analysis (DMA) 55 2.5.7. Computer simulation 55 3. Results and Discussion 56 3.1 Rheological properties of PETG/SEP composite filaments 56 3.1.1. Rheological properties of molten state of PETG-SEP composite 56 3.1.2. Rheological properties of solid state of PETG-SEP composite 61 3.2 Mechanical properties of 3D printed samples 63 3.3 Morphological properties of PETG/SEP composites. 66 3.3.1. Observation of sepiolite by SEM 66 3.3.2. Observation of post-tensile fracture surface of injection-molded PETG composite by SEM 68 3.3.3. Observation of post-tensile fracture surface of horizontal direction 3D printed PETG composite by SEM 72 3.3.4. Observation of post-tensile fracture surface of vertical direction 3D printed PETG composite by SEM 76 3.3.5. Observation of 3D printed PETG composite by TEM 80 3.4 Anisotropic structure of SEP in the PETG 82 3.4.1. Orientation characteristics of SEP in injection molded composites 82 3.4.2. Orientation characteristics of SEP in 3D printed composites 84 3.4.3. Orientation characteristics of SEP in 3D printed composites in case of after tensile deformation 86 3.5 Simulation of the reinforcement effect of SEP in PETG 88 4. Conclusions 92 Chapter 3 UV curable polymer nanocomposites with inorganic nanofillers for 3D printing 94 1. Introduction 95 2. Experimental 98 2.1. Materials 98 2.2. Material mixing method and curing process 101 2.3. Characterizations 105 2.3.1. Rheological properties of surrey state composites 105 2.3.2. Rheological properties change during photocuring behavior 105 2.3.3. Rheological properties of photo cured composite materials 106 2.3.4. Mechanical Properties 106 2.3.5. Morphological properties 106 3. Results and Discussion 107 3.1 Rheological properties 107 3.1.1. Rheological properties of surrey state composites 107 3.1.2. Rheological properties change during photocuring behavior 110 3.1.3. Rheological properties of photo cured composite materials 112 3.2. Mechanical Properties 114 3.2.1. Tensile properties 114 3.2.2. Elastic modulus 115 3.2.3. Elongation at break 116 3.3. Transmission Electron microscopy (TEM) analysis 118 4. Conclusions 120 Chapter 4 Embedded DIW 3D printing of UV curable resin/sepiolite composites with nano orientation 122 1. Introduction 123 2. Experimental 127 2.1. Materials 127 2.2. Preparation of supporting matrix 129 2.3. Preparation of photocurable resin and sepiolite composite resin 129 2.4 Preparation of specimens 132 2.4.1. Digital light processing (DLP) 3D printing 132 2.4.2. Embedded DIW 3D printing (EMB3D) 132 2.4.3. Post curing of 3D printed materials 133 2.5 Characterizations 137 2.5.1. Rheological properties of supporting matrix 137 2.5.2. Rheological properties of photocurable resin 137 2.5.3. Rheological photocuring properties 138 2.5.4. Tensile test 138 2.5.5. Transmission electron microscopy (TEM) 139 2.5.6. Scanning electron microscope (SEM) 139 2.5.7. Dynamic mechanical analysis (DMA) 139 3. Results and Discussion 141 3.1 Rheological properties of matrix 141 3.1.1. Supporting matrix are rheologically considered in EMB3D printing 141 3.1.2. Rheological shear-thinning properties of supporting matrix 144 3.1.3. Yielding property of supporting matrix 147 3.1.4. Recovery property of supporting matrix 149 3.2. Rheological properties of photocurable composite resin 151 3.2.1. Rheological shear-thinning properties of photocurable composite resin 151 3.2.2. Yielding property of photocurable composite resin 155 3.2.3. Recovery property of photocurable composite resin 157 3.2.4. Rheological properties of photocurable composite resin at photocuring 159 3.2. Mechanical properties of 3D printed samples 161 3.2. Dynamic mechanical properties of 3D printed samples 167 3.3 Morphological properties of 3D printed samples. 169 3.3.1. Observation of sepiolite by SEM 169 3.3.2. Observation of post-tensile fracture surface of DLP printed sepiolite composite by SEM 171 3.3.3. Observation of post-tensile fracture surface of EMB3D printed sepiolite composite by SEM 173 3.3.5. Observation of EMB3D printed composite by TEM 175 4. Conclusions 177 Chapter 5 Concluding remarks 179 5.1. 3D printing of PETG/sepiolite composites with nano orientation 180 5.2. Behavior and properties of UV curable polymer nano composites based on inorganic nano fillers for 3D printing 181 5.3. Embedded DIW 3D printing of UV curable resin/sepiolite composites with nano orientation 182 5.4. Concluding 183 References 185 초 록 204Docto

鍾路2街 商業建築物의 街路邊 立面 變化에 관한 硏究

학위논문(석사)--서울대학교 대학원 :건축학과,2004.Maste

인도네시아 천연 열대림 보전을 위한 클론임업 사례 연구

학위논문(석사)--서울대학교 대학원 :산림자원학과,2004.Maste