臺灣博碩士論文加值系統

此論文將以藍光晶片激發鈦酸鹽類紅色螢光粉應用於白光LED之研究，其目標為改善演色性，並使白光LED從冷白光偏向暖白光移動，增加人眼舒適度。在螢光粉的文獻研究中，發現錳離子(Mn4+)佔據於六配位的晶格中，會發出紅光色波段。因此，本研究是以Li2MgTiO4為摻雜主體，因為此結構由[LiO6]，[MgO6]和[TiO6]等元素所組成八面體結構中含有相當豐富的六配位環境，十分適合發光中心錳離子的進入。
以固態反應法合成Hf4+共摻Mn4+於Li2MgTiO4主體，並發出深紅色波段的光(~680 nm )，其中XRD並無雜相之產生，表示Hf4+進到主體時並沒有破壞原有的結構。由於摻雜了Hf4+離子，增加了Mn4+和Mn4+之間的間距，進而減少了濃度淬滅的發生並使發光強度提升了1.45倍，也同時改善了此螢光粉之熱穩定性，其中外部效率也由9% 提升至16%。而元件封裝的部分，由低溫燒製的碲玻璃粉取代矽膠(Silicone)混合螢光粉，而此方式稱之為phosphor-in-glass (PiG)，並利用WO3摻雜於TeO2-B2O3-ZnO-Na2O (TBZN) 碲玻璃系統中，大幅地提升其透明度，穿透度從67%增加至80%，同時也調整了玻璃的折射率達到和YAG：Ce3+螢光粉相匹配的1.83。PiG型WLED的合成是利用商用黃色螢光粉YAG：Ce3+以及上述之紅色螢光粉混入自製之玻璃粉燒製而成，其中，紅色螢光粉並無玻璃的二次燒結製成而產生化學變化，展現出相對穩定性。PiG型WLED之演色性由72.8提升至83.3改善約14.5% 的幅度，色溫則是由5311 K減少致4570 K，而其熱穩定性以及顏色穩定性的測試中都優於傳統矽膠之封裝方式。

Issues of phosphor-converted white light-emitting diodes (pc-WLEDs) such as lack in red component and degradation of silicone package (phosphor-in-silicone, PiS) are still a big challenge for practical application. Hence, phosphor-in-glass (PiG) becomes a substituted way which is a method of LED fabrication by mixing low-melting glass powder and phosphors to improve above-mentioned problems. In this thesis, a series of Li2MgTiO4:Mn4+, Hf4+ co-doped red phosphors were synthesized by solid-state reaction. This co-doped phosphor shows a deep red emission around 680 nm due to 2Eg → 4A2g transition and with addition of Hf4+ dopants, the external quantum efficiency (EQE) increased from 9% to 16%. Furthermore, the thermal stability has been improved and the intensity of rad part also enhanced by 1.45 times. In the aspect of package, low-melting glass component of TeO2-B2O3-ZnO-Na2O doped with WO3 shows a high transmittance above 80% and has a good match RI of YAG:Ce3+ phosphor (1.83). A warm PiG-based WLED is fabricated successfully, which is combined with commercial YAG:Ce3+ and Li2MgTiO4:Mn4+, Hf4+ red phosphor in TeO2-B2O3-ZnO-Na2O-WO3 glass matrix. The color rending index (CRI) of PiG-based WLED increased from 72.8 to 83.3 which was improved by 14.5% and the correlated color temperature (CCT) shifted from bluish white (5311 K) to warm white (4570 K) under driven current of 350 mA. Moreover, the results of thermal stability and color stability between PiS- and PiG-based WLEDs have been compared and investigated in this thesis.

Table of Contents
Abstract II
摘要 III
致謝 IV
List of Tables VIII
List of Figures IX
Chapter 1 Introduction 1
1-1 Background 1
1-2 Motivation 2
1-2-1 Improvement of the CRI 2
1-2-2 Enhancement of encapsulant 4
Chapter 2 Fundamentals and Literature Reviews 5
2-1 Theories of fluorescent material 5
2-1-1 Optically active centers 5
2-1-2 Transition metal ions 6
2-1-3 3dn Sugano–Tanabe diagrams 6
2-2 Optical properties of phosphor 8
2-2-1 Introduction of luminescence 8
2-2-2 Photoluminescence and absorption spectra 10
2-2-3 Phenomena of stoke shift 13
2-2-4 Nonradiative tansitions 15
2-2-5 Energy transfer 16
2-2-6 Thermal quenching 17
2-3 Structural theories of glass 19
2-3-1 Formation of glass 19
2-3-2 Structural roles of glass 20
2-3-3 Zachariasen rule for glass formation 20
2-3-4 Properties of bond strength 21
2-3-5 Non-bridging oxygen (NBO) and bridging oxygen (BO) 23
2-3-6 Diffraction pattern 24
2-3-7 Devitrification effect 25
2-4 Overview of Li2MgTiO4:Mn4+ phosphor 26
2-5 Inorganic encapsulants of phosphor 28
2-6 Overview of phosphor-in-glass (PiG) 29
Chapter 3 Experimental 31
3-1 Raw materials and InGaN LED chip 31
3-2 Experimental procedures 32
3-2-1 Li2MgTiO4：Mn4+, Hf4+ red phosphor 33
3-2-2 Preparation of glass powder 34
3-2-3 Fabrication of PiG-based WLEDs 36
3-3 Instrument characterization 37
3-3-1 Fluorescence spectrophotometer 37
3-3-2 X-ray diffraction (XRD) 39
3-3-3 Temperature controller 39
3-3-4 TGA/DSC 40
Chapter 4 Results and Discussions 41
4-1 Li2MgTiO4:Mn4+, Hf4+ phosphor 41
4-1-1 XRD analysis 41
4-1-2 Photoluminescence properties 45
4-1-3 Tanabe-Sugano diagram analysis 48
4-1-4 Thermal stability analysis 50
4-2 TeO2-based glass analysis 53
4-2-1 TeO2-B2O3-ZnO-Na2O-Al2O3 glass 53
4-2-2 TeO2-B2O3-ZnO-Na2O-WO3 glass analysis 55
4-3 Phosphor-in-glass (PiG) plate for WLED 64
4-3-1 Design for PiG-based WLED 64
4-3-2 PL/PLE spectra and XRD Analysis 65
4-3-3 EL Spectra 70
4-4 Comparison between PiG and PiS 72
4-4-1 Thermal stability 72
4-4-2 Color stability 74
Chapter 5 Conclusions and Future Work 77
5-1 Conclusions 77
5-2 Future Works 79
References 80

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