Title Page

Abstract

요약

Contents

Chapter 1. General Introduction 21

1.1. Scientific Context 21

1.2. Objective and Outline of Dissertation 22

References 24

Chapter 2. Theory Background 27

2.1. Fluorescent emitter 27

2.1.1. Background of Fluorescence Phenomenon 27

2.1.2. Colloidal Nanocrystal quantum dots 29

2.2. Surface Plasmon Resonance 33

2.2.1. Propagating Surface Plasmon Resonance (PSPR) 34

2.2.2. Localized Surface Plasmon Resonance 35

2.3. The interaction of plasmons and fluorescent emitters 36

2.3.1. Strong coupling 36

2.3.2. Weak coupling 37

2.4. Application on Photonics Devices 41

2.4.1. Display Technology 41

2.4.2. Photovoltaics 43

References 46

Chapter 3. Enhanced Performance in Photovoltaic Cells via Gold Nanoparticles decorated CdSe/ZnS Quantum dots 53

3.1. Introduction 54

3.2. Experimental Section 55

3.3. Results and Discussion 56

3.3.1. Gold nanoparticles Characterization 57

3.2.2. Effect of Au/QDs hybrid on Photovoltaics 61

3.4. Conclusion 64

References 66

Chapter 4. Photoluminescence Properties of CdSe/ZnS QDs Donor-Acceptor via Plasmon Coupling of Metal Nanostructures and Application on Photovoltaic Devices 70

4.1. Introduction 71

4.2. Experimental Section 73

4.3. Results and Discussion 75

4.3.1. Tuning the Fluorescence of CdSe/ZnS QDs using large size Au NPs-47nm with Silica coating 76

4.3.2. Tuning the Fluorescence of CdSe/ZnS QDs using medium-size Au NPs-24 with Silica coating 79

4.3.3. Tuning the Fluorescence of CdSe/ZnS QDs using medium-size Au NPs-4.6 with Silica coating 85

4.3.4. Effect of hybrid nanostructures on Photovoltaics 90

4.4. Conclusion 91

References 93

Chapter 5. Passive radiative cooling and colour effect through multi-functional Silica/Silver decorated Quantum dot for Photovoltaic application 97

5.1. Introduction 98

5.1.1. Introduction to Radiative Cooling and Literature Review 100

5.2. Experimental Section 103

5.3. Results and Discussion 106

5.3.1. Synthesized SiO₂@Ag particles 106

5.3.2. Synthesized CdSe/ZnS QDs decorated SiO₂@Ag particles 112

5.3.3. Effect of LSPR light scattering on Photovoltaics 116

5.4. Conclusion 122

References 123

Chapter 6. The encapsulation of Quantum Dots onto Silica Microspheres in Polymer films for Photonic Devices 129

6.1. Introduction 130

6.2. Experimental Section 131

6.3. Results and Discussion 134

6.3.1. Analysis of QDs/SiO₂ hybrid particles powder 134

6.3.2. CdSe/ZnS QDs decorated SiO₂@Ag particles 138

6.3.3. Optical properties of QDs@SiO₂/EVA on blue LED performance 140

6.4. Conclusion 142

References 143

Chapter 7. General Conclusion and Perspective 147

7.1. General Conclusion 147

7.2. Perspectives 148

Appendix 150

Experimental methods 150

Synthesis and Characterization of CdSe/ZnS QDs 150

Materials characterization 151

Device performance characterization 152

References 153

List of Publications 153

Publications Contributing to This Dissertation 153

Additional Publications & Conference Proceeding 153

Table 2-1. Literature Review on QD LED enhancement. 42

Table 3-1. Summary data of synthesized oleylamine capped gold nanoparticles (OLA-GNPs) 60

Table 3-2. J-V characteristics of reference cell, GNPs-OLA 3 cell and GNPs-OLA 3/QDs composite cell measured under the artificial light. 64

Table 4-1. Estimated average lifetime, Radiative rate, Non-radiative rate and Energy transfer efficiency of Au@SiO₂/QDs hybrid structures. 84

Table 4-2. The separation distance for quenching efficiency between QDs and Au/Au@SiO₂ NPs. 90

Table 5-1. Elementary composition analysis of SiO₂ and SiO₂@Ag particles 109

Table 5-2. J-V characteristics of CIGS cells with/without QDs/SiO₂@Ag particles. 118

Table 5-3. Summary of recent radiative cooling researches gathered from literatures. 121

Table 6-1. Elementary composition analysis of MQDS and SQD particles 136

Table 6-2. Emission data of QDs and SiO₂ structures with EVA film. 140

Figure 2-1. Fluorescence absorption and emission processes illustrated by the Jablonski diagram. 28

Figure 2-2. (a) Schematic of QDs illustration. (b) Nor. Fluorescence intensity of ten distinguishable emission colours of ZnS-capped CdSe QDs excited with a near-UV lamp. From left to right, the... 30

Figure 2-3. Schematic illustrate (a) The generation of single and multiple exciton in QDs. (b) Electronic energy levels depending on the number of bound atoms. 31

Figure 2-4. Schematic diagram illustrated formation process of (a) Epitaxial QDs. (b) Colloidal QDs.. 32

Figure 2-5. Ligand passivation reduces non-radiative recombination and enhances the PLQY of colloidal quantum dots. 33

Figure 2-6. Schematics of (a) Propagating surface plasmon resonance. (b) Localized surface plasmon resonance of metal nanospheres. 34

Figure 2-7. Diagram of the reflection spectra displays the outcomes of the intense interaction between light and matter. The microcavity (representing light) and the matter (exciton layer) have resonant... 37

Figure 2-8. (a) Diagram of the experimental setup. The insert shows the scanning electron microscope (SEM) image of a gold particle connected to the tip of a sharp optical fiber. (b) Fluorescence rate plotted... 40

Figure 2-9. Schematic illustrated the design framework for a complete range of highly transparent QLEDs, showcasing blue, green, red, and tri-color QLEDs. 41

Figure 2-10. Schematic of Devices structures (a) the QLEDs embedded Ag nano-islands. (b) All-inorganic QD-LEDs with QD-capped Au layer. (c) CdSe/ZnS QD-LEDs with colloidal Au NPs... 42

Figure 2-11. Schematic of (a) AM1.5 solar spectrum and the description of the light incident absorbed in a 2-μm-thick crystalline Si film (in case single-pass absorption and no reflection). (b) Plasmonic... 43

Figure 2-12. Overview of generalized scatterers used to channel light into waveguide modes within a solar cell. These scatterers can be positioned on the upper surface (1), within the core (2), or at the base... 44

Figure 2-13. (a) Schematic illustrated the optical absorption and optical loss process with a LDS layer on top of PV module and Fitting of experimental EQE spectra of solar cells with LDS layers (literature... 45

Figure 3-1. Synthesis process for Au NPs-OLA. Img.1a to 1d-Synthesis process for small Au NPs. Img. 2a to 2d-Growth reaction process for large Au NPs. 56

Figure 3-2. Schematic of device fabrication process. 56

Figure 3-3. TEM images and distribution histogram of Au NPs-4.6. 57

Figure 3-4. TEM images and distribution histogram of Au NPs-12.3. 58

Figure 3-5. TEM images and distribution histogram of Au NPs-18.3. 58

Figure 3-6. TEM images and distribution histogram of Au NPs-24.7. 58

Figure 3-7. TEM images and distribution histogram of Au NPs-47.4. 59

Figure 3-8. (a) Normalized absorption spectra of Au NPs. (b) Absorption spectra of Au NPs and Emission spectra of CdSe/ZnS QDs. (c) Absorption extinction spectra of Au NPs-QDs conjugates. (d)... 60

Figure 3-9. (a) Current density versus voltage curves. (b) Incident photon to current conversion efficiency (IPCE) spectra of all devices. (c) Energy band diagram at the equilibrium condition. 61

Figure 3-10. J-V characteristics of n-Si solar cells with GNPs/QD. 63

Figure 3-11. Variation of photovoltaic characteristics extracted for all devices with different diameters of Au NPs (a) J SC and V OC . (b) Fill factor and Efficiency. (c) Series resistance and Shunt resistance. 64

Figure 4-1. Synthesis of hybrid nanostructures flowchart. 73

Figure 4-2. The processing steps for fabricating solar cells. 74

Figure 4-3. (a) Schematic of the preparation for the composite of silica-coated gold nanoparticles and quantum dots (Au@SiO₂ @QDs). (b) FTIR spectra of pure oleylamine (OLA) and Au@SiO₂ NPs. 75

Figure 4-4. (a) QDs-Au NPs conjugates. (b-c) QDs-AuNPs-24@SiO₂ conjugates. 76

Figure 4-5. TEM images of (a) Au NPs-47, (b) Au-47@SiO₂-16, (c) Au-47@SiO₂-30. 76

Figure 4-6. Absorbance extinction spectra of Au@SiO₂. 77

Figure 4-7. The effect of Au NPs@SiO₂ on the PL spectra of (a) QDs-528. (b) QDs-627. The inset shows the dependence of PL intensity on the SiO₂ thickness. 78

Figure 4-8. TEM images of (a) Au NPs-24, (b) Au-24@SiO₂-15, (c) Au-24@SiO₂-26. 79

Figure 4-9. Normalized Absorbance spectra of Au-24@SiO₂. 80

Figure 4-10. (a) The effect of Au-24@SiO₂ on the PL spectra of QDs-528 nm. The inset shows the dependence of PL intensity on the SiO₂ thickness. (b) PL decay curves of QDs-528/Au-24@SiO₂... 81

Figure 4-11. (a) The effect of Au-24@SiO₂ on the PL spectra of QDs-528 & QDs-627 combination. (b) The dependences of PL enhancement factor IPL/IPL,₀ of QDs-627 and QDs-528 and PL ratio...[이미지참조] 83

Figure 4-12. TEM images of (a) Au NPs-4.6, (b) Au-4.6@SiO₂-4.8, (c) Au-4.6@SiO₂-10.7. 85

Figure 4-13. Normalized Absorbance spectra of Au-4.6@SiO₂. 86

Figure 4-14. (a) The effect of Au-4.6@SiO₂ on the PL spectra of QDs-528 nm. The inset shows the dependence of PL intensity on the SiO₂ thickness. (b) PL decay curves of QDs-528−Au-4.6@SiO₂... 87

Figure 4-15. (a) The effect of Au-4.6@SiO₂ on the fluorescence spectra of QDs-528 and QDs-627 combination. (b) The dependences of PL enhancement factor IPL/IPL,₀ and PL ratio IPL(A)/I PL(D) on SiO₂...[이미지참조] 88

Figure 4-16. (a) Photovoltaic characteristics extracted for devices W/Wo hybrid structure. (b) Current density versus voltage curves. (c) Incident photon to current conversion efficiency (IPCE) spectra of all... 91

Figure 5-1. (a) Schematic for the energy balance of solar cells. (b) AM 1.5 solar spectrum (yellow) and the atmospheric transmittance spectrum (steel blue). 101

Figure 5-2. SiO₂@Ag structures with two synthesized methods 104

Figure 5-3. Schematic illustration of QDs blending process on SiO₂@Ag structures and CIGS solar cell with QDs decorated SiO₂@Ag plasmonic and scattering layer. 105

Figure 5-4. XRD patterns of SiO₂ and SiO₂@Ag particles 107

Figure 5-5. TEM images and distribution histogram of (a-c) SiO₂@Ag-13.3. (d-f) SiO₂@Ag-20.2. 107

Figure 5-6. EDS mapping of individual elements in SiO₂@Ag-20.2. 108

Figure 5-7. EDX analysis of SiO₂@Ag-13 and SiO₂@Ag-20. 109

Figure 5-8. (a) XPS survey spectrum. XPS analysis of (b)-(c) SiO₂ spheres. (d)-(e) SiO₂@Ag-13.3. (g)-(i) SiO₂@Ag-20.2. 110

Figure 5-9. Normalized absorption spectra of SiO₂, SiO₂@Ag-13.3 and SiO₂@Ag-20.2. 111

Figure 5-10. EDS mapping of individual elements in (a) SiO₂@Ag-13.3. (b) SiO₂@Ag-20.2 with QDs. 113

Figure 5-11. (a) Absorption extinction spectra of SiO₂ and SiO₂@Ag on SLG with the emission spectra of QDs. (b) Absorption extinction spectra of SiO₂@Ag-QDs conjugates. 113

Figure 5-12. (a) The effect of SiO₂@Ag on the PL intensity of QDs. The inset shows the dependence of PL intensity on the Ag NPs size. (b) Schematic diagram of SiO₂@Ag enhanced QDs' PL. 115

Figure 5-13. (a) PL decay curves of QDs/SiO₂@Ag conjugates. (b) Energy transfer of (1) Ag NPs with a direct contact to QDs. (2) SiO₂@Ag-13.3 particles contact to QDs. (3) SiO₂@Ag-20.2 particles... 115

Figure 5-14. (a-d) Current density versus voltage curves of bare cells (short dash line) and cells integrated QDs/SiO₂@Ag (solid line). Variation of photovoltaic characteristics extracted for all devices.... 117

Figure 5-15. (a) The atmospheric transmittance spectrum (steel blue) and the calculated IR emissivity of CIGS cells with/without QDs/SiO₂@Ag particles (2-12.5 μm). (b) AM 1.5 solar spectrum (orange)... 119

Figure 5-16. (a) Temperature of cells under different solar simulator illumination. (b) Temperature rise and decrease of cells under Tungsten light at 450 W m¯². Stabilized temperature distribution for cells... 119

Figure 5-17. Outdoor measurement (a) experimental setup (b) environmental conditions (October 03-05, 2023). Radiative cooling performances and temperature differences compared with the reference... 120

Figure 6-1. (a-b) Schematics of Silanized-QD assembled in SiO₂ spheres. Photo of CdSe/ZnS QDs (c) Initial product. (d) Final product. 132

Figure 6-2. (a-b) Schematics of Silanized-QD assembled in SiO₂ spheres synthesized process. Photo of CdSe/ZnS QDs (c) Initial product. (d) QDs-adsorbed MPS-SiO₂. (e) Final product. 133

Figure 6-3. TEMimages of (a)MQDS. (b)MPS-SiO₂ spheres and QDs adsorbed SiO₂ spheres process. (c) SQD. (d) SQDS. 134

Figure 6-4. EDS mapping of individual elements in (a) MQDS. (b) SQD. 135

Figure 6-5. XRD Patterns. (b) FT-IR spectra of CdSe/ZnS QDs, SiO₂ spheres, MQDS, SQD, SQDS. 136

Figure 6-6. (a) UV−vis absorbance and (b) PL spectra of Green QDs, MQDS, SQD, and SQDS. 138

Figure 6-7. FT-IR spectra QDs, MQDS, SQD, and SQDS in the distinct segments of wavenumber (a) 4000~800 cm¯¹. (b) 3840~3030 cm¯¹. (c) 1185~985 cm¯¹. 138

Figure 6-8. Photos of QDs/SiO₂/EVA film (a) under room light and (b-c) under UV light (365 nm). (d) The uniformity analysis of QDs/EVA film. (e) PL intensity of Bare QDs, MQDS, SQD, and SQDS... 139

Figure 6-9. (a) Photos of QD film package for EL characteristic (1) Blue Flip chip. (2) Metal package. (3) KOPTI blue LEDs. (b) Photos of QDs films on blue-LEDs (a) before measurement. (b) after... 140

Figure 6-10. The optical properties of Bare QDs/EVA,MQDS/EVA, SQD/EVA, SQDS/EVA films (a) EL intensity under 40, 120, and 200 mA. (b) Luminescence intensities of green light versus driving... 141