請用此 Handle URI 來引用此文件:
http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/21673
標題: | 應用於發光二極體背光顯示器之Cs4PbBr6鈣鈦礦奈米晶體發光特性研究 Luminescence Properties of Cs4PbBr6 Perovskite Nanocrystals for the Application in Light-Emitting Diode Backlight Display |
作者: | Yu-Jui Tseng 曾于芮 |
指導教授: | 劉如熹(Ru-Shi Liu) |
關鍵字: | 鈣鈦礦,奈米晶體,微乳膠合成法,發光特性,廣色域面積, Perovskite,Nanocrystals,Microemulsion synthesis,Luminescence properties,Wide color gamut, |
出版年 : | 2019 |
學位: | 碩士 |
摘要: | 近年,因零維Cs4PbBr6鈣鈦礦奈米晶體具良好之熱穩定性與出色之光學性質而被視為新一代具潛力性之發光材料,引發許多學者之興趣進而相繼研究其性質。零維鈣鈦礦奈米晶體不僅保留傳統鈣鈦礦奈米晶體半高寬窄、吸收度高與量子效率高之光學性質,更為鈣鈦礦奈米晶體存在已久之穩定性問題注入一劑強心針。然而,零維Cs4PbBr6鈣鈦礦奈米晶體其可見光之放光來源仍具爭議性。為解決此爭議,本研究嘗試以實驗與光譜之方法釐清爭議。
本研究首先以微乳膠法成功合成Cs4PbBr6奈米晶體,並利用高溫變溫螢光光譜測定其結構於溫度之耐受性,得知其經150oC高溫烘烤恢復後仍維持96%放光強度。為得知其光學性質,於室溫與低溫變溫之螢光光譜發現Cs4PbBr6與CsPbBr3之光學行為相似,然而先前文獻指出Cs4PbBr6之能隙高達3.9 eV,且經由同步輻射XRD鑑定於本研究並未發現CsPbBr3相之存在,因此得知為Cs4PbBr6內生成CsPbBr3團簇發光中心,使Cs4PbBr6發出綠光。同時由室溫光譜得知Cs4PbBr6於310 nm波段具強吸收力,卻無法受此波段激發而放光,於低溫光譜卻發現當溫度低於200 K,Cs4PbBr6受310 nm光激發出現375 nm與518 nm之雙重放光,證明了能量轉移之現象,亦可得知室溫下由於熱淬滅效應而使螢光淬熄。此外,本研究假設Cs4PbBr6奈米晶體內之Cs+缺陷增加,使鄰近之八面體單元彼此集合,形成鹵素共享之CsPbBr3團簇作為發光中心,因此藉調控不同Cs/Pb前驅物比例之實驗證實,並用量子效率儀量測其放光效率,當Cs/Pb比例下降至2.5時,所得之產物Cs4PbBr6奈米晶體維持純相且外部量子效率提升,證實晶體中由Cs+缺陷引起之CsPbBr3團簇乃其高效率放光之原因;於Cs/Pb比例小於等於2.5時,所得之產物隨Cs/Pb比例減少,CsPbBr3雜相含量逐漸增加且外部量子效率迅速降低,說明晶體之發光非CsPbBr3雜相所致。最後利用變壓螢光光譜得知Cs4PbBr6奈米晶體於不同壓力下之光學特性影響,並以時間解析光譜追蹤其放光性質變化。 與傳統之CsPbBr3相比,Cs4PbBr6奈米晶體具較佳之結構穩定性與耐受性,使其於白光發光二極體之背光顯示器應用具更佳之表現,同時本研究亦成功釐清了Cs4PbBr6之發光來源之爭議。本研究將Cs4PbBr6奈米晶體以藍光發光二極體晶片與次毫米發光二極體晶片進行封裝,封裝光譜於CIE圖之色座標為(0.27,0.24),色域面積達彩色電視廣播標準,具NTSC 129%與126%之廣色域,且色純度高,顯示Cs4PbBr6奈米晶體為一極具潛力之背光顯示器用發光材料。 In recent years, the zero-dimensional Cs4PbBr6 crystals are respected as the new generation of functional materials for their good thermal stability and optical performance. Not only do the zero-dimensional perovskite Cs4PbBr6 nanocrystals retain the optical properties of traditional perovskite nanocrystals with a narrow full width at half maximum (FWHM) of ∼20 nm, high absorbance and high quantum efficiency, but they also solve a long-lasting stability problem in perovskite nanocrystals. However, the mechanism of the green emission from the Cs4PbBr6 crystals is still under debate. In order to solve this controversy, we attempt to clarify the controversy by using fluorescence spectrometer and confirm that the green light source of Cs4PbBr6. In this study, the Cs4PbBr6 nanocrystals were successfully synthesized by low-temperature microemulsion method. The temperature tolerance of the structure was determined by temperature-dependent fluorescence spectroscopy. It was found that the 96% emission intensity was maintained after the high-temperature heating at 150oC. About the optical properties, the fluorescence behaviour of Cs4PbBr6 and CsPbBr3 were similar at low temperature. However, the previous literature pointed out that the band gap of Cs4PbBr6 is about 3.9 eV, so it should not emit the green light. Furthermore, the synchrotron XRD didn’t show the existence of CsPbBr3 phase. We proposed that it generated CsPbBr3 clusters which cause the strong green light in Cs4PbBr6 crystals. At the same time, we found that Cs4PbBr6 has strong absorption at 310 nm, but it could not be stimulated. However, when the temperature was lower than 200 K, Cs4PbBr6 emitted the light in 375 nm and 518 nm. This phenomenon proved the energy transfer, and it also showed the thermal quenching effect at room temperature. In addition, we hypothesized that the Cs+ vacancies in the Cs4PbBr6 nanocrystals induced the formation of CsPbBr3 clusters and we proved it by adjusting the ratio of different Cs/Pb precursors. While the Cs/Pb ratio decreased to 2.5, the quantum efficiency kept increasing and the product maintained the pure Cs4PbBr6 phase. It can be confirmed that the CsPbBr3 clusters were the reason for high quantum efficiency. When the Cs/Pb ratio was less than 2.5, the quantum efficiency quickly decreased and the CsPbBr3 impurity phase appeared. It indicated that the green light was not caused by the CsPbBr3 impurity. The optical properties of Cs4PbBr6 nanocrystals under different pressures were also determined by pressure-dependent fluorescence spectroscopy. Compared with the traditional CsPbBr3 nanocrystals, the Cs4PbBr6 nanocrystals possess better stability and tolerance in environmental factors. These advantages make Cs4PbBr6 have better performance in the backlighting used light emitting diode. About the mechanism of the green light from the Cs4PbBr6 crystals, we also successfully clarified the debate. Finally, the Cs4PbBr6 crystals were succeeded fabricating as traditional WLED and Mini-LED which achieved high color gamut of 129% and 126% and proved Cs4PbBr6 nanocrystals are the potential material for backlight application. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/21673 |
DOI: | 10.6342/NTU201900966 |
全文授權: | 未授權 |
顯示於系所單位: | 化學系 |
文件中的檔案:
檔案 | 大小 | 格式 | |
---|---|---|---|
ntu-108-1.pdf 目前未授權公開取用 | 5.96 MB | Adobe PDF |
系統中的文件,除了特別指名其著作權條款之外,均受到著作權保護,並且保留所有的權利。