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標題: | 量子點發光材料之合成鑑定與發光二極體應用 Quantum dots Materials: Synthesis, Characterization, and Application in Light-Emitting Diodes |
作者: | Hung-Chia Wang 王宏嘉 |
指導教授: | 劉如熹(Ru-Shi Liu) |
關鍵字: | 量子點,白光發光二極體,量子點式有機發光二極體, quantum dots,white-light LEDs,quantum dot light-emitting diodes, |
出版年 : | 2018 |
學位: | 博士 |
摘要: | 量子點具可藉溶液法製備、易加工、波長可調性與量子效率高等突出特點,非常適合光電領域之應用,本研究主要研究量子點其於白光發光二極體(white-light LEDs)與量子點式有機發光二極體(quantum dots LEDs; QLED)之應用。本研究主要分成三部份,分別為(1)鈣鈦礦量子點應用於光激放光式白光發光二極體、(2)鈣鈦礦量子點應用於電激放光式有機發光二極體、(3)無鎘量子點應用於電激放光式有機發光二極體。鈣鈦礦量子點因其放光光譜較窄,非常適用於廣色域顯示。然因量子點存在表面缺陷、熱穩定性差與鹵素易離子交換之缺點,使其於白光發光二極體之應用受限。本研究乃提出利用多孔性二氧化矽材料合成鈣鈦礦量子點複合材料,所得之多孔性鈣鈦礦量子點粉末具較佳之熱穩定性與耐水性,並為窄譜帶綠色螢光材料,將其應用於背光顯示之晶片型白光發光二極體, 在通過濾色片後計算之色域值較傳統含鎘量子點高,其白光發光二極體之色域可達 NTSC 113%之結果。此外,電致發光量子點有機發光二極體技術近年也愈來愈受重視,QLED像OLED一樣屬自發光背光模組,不需要背光源,並且實現柔性顯示,卻不存在OLED的缺陷,是一個顛覆性的技術革新。本研究亦將探討鈣鈦礦量子點與無鎘磷化銦應用於此電致發光元件之潛力。本研究第二部分為鈣鈦礦量子點應用於電激放光式有機發光二極體,簡單之熱注射方式合成鈣鈦礦量子點,以較穩定之Sn4+部分取代之Pb2+。其中Sn4+ doped CsPbBr3樣品之絕對量子效率從45%提高至83%。並由飛秒瞬態吸收、時間解析螢光光譜與單粒子光譜之分析鑑定,獲得量子效率提升之原因為Sn4+之取代使鈣鈦礦量子點中帶電激子(trion)之形成減少。此高量子效率之Cs(Pb0.67Sn0.33)Br3製成之量子點式有機發光二極體之元件表現明顯提升,元件電流效率(current efficiency)為11.63 cd/A,外部量子效率為4.13%,此元件表現為目前含錫鈣鈦礦量子點式有機發光二極體中表現最優異者。第三部分為磷化銦量子點應用於電激放光式有機發光二極體,本研究合成之厚殼層磷化銦量子點效率可達70%,其應用於發光二極體之穩定性佳,且旋塗成薄膜後可避免以下問題 (1)量子點之間之螢光共振能量轉移(FRET)、(2)俄歇複合(Auger recombination)、(3)減少水氧之影響。其應用於倒置式(Inverted)有機發光二極體裝置,可達放光強度(luminescence) 10000 cd/m2 、電流效率4.4 cd/A與功率效率(power efficiency) 4.32 lm/w,發光強度與能量效率為目前文獻中最佳表現之無鎘QLED裝置。 Quantum dots (QDs) attracted significant interests in recent years because of their unique optical properties, such as tunable wavelength, narrow emission, high photoluminescence quantum efficiency (PLQY) and facile solution synthesis. Our quantum dot research could be divided into three major part, (1) perovskite quantum dots (PQDs) used in white-light LEDs, (2) Perovskite quantum dots used in quantum dots light-emitting diodes (QLEDs), (3) Cd-free Indium phosphide quantum dots application in QLEDs. The stability of PQDs requires further improvement to prevent their degradation by temperature, oxygen, moisture, and light. In this thesis, we used mesoporous silica integrated with perovskite quantum dots. This MP-CsPbBr3 nanocomposite show the highly thermal and water resistant. All-inorganic PQDs in white-light LEDs for backlight application. The color gamut overlap of the NTSC space was approximately 113% which is higher than previously phosphor and Cd QDs based white-light LEDs. Furthermore, we demonstrate a hot-injection synthesis of CsPb1-xSnxBr3 perovskite QDs with Sn(IV) substitution. Moreover, Sn(IV) doping can effectively suppress the formation of trions, as revealed by the measurement of single-dot, time-resolved PL, and TA spectroscopies. The best perovskite QLED device displays a luminescence of 12,500 cd/m2, a CE of 11.63 cd/A, an EQE of 4.13%, a power efficiency 6.76 lm/w, and a low turn-on voltage of 3.6 V, which are the highest values among reported Sn-based perovskite QLEDs. Finally, the thick-shelled green InP/ZnSeS/ZnS cadmium-free QDs were used in the inverted QLED device. Cadmium-free thick-shelled InP/ZnSeS/ZnS heter-ostructured quantum dots (QDs) were synthesized using the heating-up approach. In this approach, the InP/ZnSeS/ZnS QDs (7.9 nm) are thicker than the InP/ZnSeS QDs. The inter ZnSeS buffer layer can decrease the lattice mismatch between the InP core and the ZnS outer passivated layer. With the increase in ZnS shell, the stability of the InP QDs can be improved when the QD solution is changed to film type during fabrication. In QLEDs, a thin-shelled InP QD film face numerous problems, such as non-radiative decay, oxygen effect, and Auger recombination. Thick-shelled InP/ZnSeS/ZnS can reduce the effect of these factors, and thus, enhance the efficiency of a QLED device. This inverted thick-shelled InP/ZnSeS/ZnS QLED device exhibits luminescence of over 10000 cd/m2, current efficiency of 4.4 cd/A, power efficiency of 4.32 lm/w, and low turn-on voltage (2.2 V). Results show the good performance of cadmium-free QLEDs. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/69650 |
DOI: | 10.6342/NTU201800967 |
全文授權: | 有償授權 |
顯示於系所單位: | 化學系 |
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