應用於紅外光發光二極體之Cs4PbI6鈣鈦礦奈米晶體

Cs4PbI6 Perovskite Nanocrystals for the Application in Near-Infrared Light-Emitting Diodes

許喬茵(Chiao-Yin Hsu)

指導教授 ： 劉如熹

國立臺灣大學/理學院/化學研究所/碩士(2020年)

https://doi.org/10.6342/NTU202001113

摘要

根據世界衛生組織最新統計，失智症(含阿茲海默症)為世界上第五大死亡原因，僅次於缺血性心臟病、腦中風、慢性肺阻塞疾病、下呼吸道感染等。全球目前平均每三秒鐘則增加一人罹患失智症，其中阿茲海默症約佔失智症之60%至70%，且死亡率亦步步攀升，因此研發治療或延緩阿茲海默症之方法已成為許多學者相繼研究之領域。於非侵入之方法中，科學家利用紅外線組織穿透性佳之特性，使用將其照射於大腦患部，促進組織之細胞生成修復。
現今微型化發光設備日益蓬勃發展，故為找尋適用於微型化發光設備之材料，本研究則以微乳膠法合成奈米級之零維鈣鈦礦Cs4PbI6晶體為紅外線之發光材料，藉由調控碘化鋅與碘化鉛之比例、銫前驅物注入反應溶劑之含量與表面有機配位體之酸鹼比例以組成最佳合成配方，再經而探討不同陽離子於合成零維Cs4PbI6之影響。經同步輻射之晶格分析與電子顯微鏡之影像鑑定，隨著摻入之碘化鋅由0 M升至0.0097 M，Cs4PbI6之比例逐漸上升，推測其原因為Zn-I之解離能小於Pb-I之解離能，此可提供足量之碘離子，使Cs4PbI6更易於形成。銫前驅物之注入量與有機配位體油胺之比例增加，亦有助於銫離子分離[PbI6]4-八面體，則可形成純相Cs4PbI6而零維鈣鈦礦Cs4PbI6之晶型為rhombohedron。利用激發放射光譜儀測量，可知此奈米晶之發光波長位置為698奈米，且半高寬為34奈米，其為一窄半高寬之近紅外光。再利用變溫光譜量測，可於低溫下觀察Cs4PbI6具兩放射峰，亦藉時間衰變光譜分析，推測奈秒級之A波長為激子放光，微秒級之B波長為缺陷態放光。將其封裝於次毫米發光二極體，並於3 V與9.3 mA下進行穿透能力實驗，於0.5公分下之肉片厚度，仍可觀測到紅外線之螢光，其強度為原先之20%。
本研究乃將鈣鈦礦Cs4PbI6材料應用於次毫米發光二極體晶片，發現其可發紅外光且其量子效率不亞於可見光之效率，並可應用於微型紅外光發光二極體，作為治療阿茲海默症方法之一。

關鍵字

鈣鈦礦 ； 紅外線 ； 微乳膠法

並列摘要

According to the latest information released by the World Health Organization, Dementia (including Alzheimer's disease) is the fifth leading cause of death in the world, next to Ischemic Heart Disease, Stroke, Chronic Obstruction Pulmonary Disease, and Lower Respiratory Tract Infections. At present, an average of one person suffers from dementia every three seconds. Alzheimer's disease accounts for about 60% to 70% of Dementia, and the mortality rate is increasing. Therefore, the development of the pharmacological and non-pharmacological methods for treating Alzheimer's disease has been investigated. In non-drug methods, scientists have developed a method that uses low-infrared light to penetrate human tissues. This method of irradiating the brain with infrared light not only promotes the growth of various types of cells but also stimulates cell repair.
Nowadays, miniaturized light-emitting devices are booming. To find materials suitable for miniaturized light-emitting devices, a zero-dimensional perovskite Cs4PbI6 nanocrystal was synthesized by the microemulsion method as infrared light-emitting materials. The ratio of zinc iodide to lead iodide, the content of cesium precursors and the acid-base ratio of the surface organic ligands have been adjusted to form the best synthetic formula, following by comparing the effects of the remaining different cations on the synthesis of zero-dimensional Cs4PbI6. By XRD of NSRRC and SEM image identification, the percentage of Cs4PbI6 gradually increased when the zinc iodide was incorporated from 0% to 57%. It is speculated that the dissociation energy of Zn-I is smaller than that of Pb-I, so iodide ions can be provided to make Cs4PbI6 easier to form. Increasing the proportion of cesium precursor and the organic ligand oleylamine also contributes to the separation of [PbI6]4-octahedron from cesium ions, which can form a pure phase Cs4PbI6. The crystal form of zero-dimensional perovskite Cs4PbI6 is Rhombohedron. The emission position measured by the excitation-emission spectrometer is 698 nm, and the full width at half maximum is 34 nm, which is a narrow near-infrared light. By temperature dependence of luminescence spectra, it can be observed that Cs4PbI6 has two emission peaks at low temperature. By time decay spectroscopy analysis, it is speculated that the nanosecond A wavelength is excitonic emission and the microsecond B wavelength is defect state emission.
The infrared-emitting material is packaged in a Mini light-emitting diode, and a penetration test of meat pieces was performed at 3 V and 9.3 mA. The fluorescence intensity at the initial penetration thickness of 0.5 cm is 20% of the original. As the thickness of the slice increases, its penetrating fluorescence intensity gradually approaches zero. The results are consistent with the performance of the previous literature.
This thesis is the application of the perovskite Cs4PbI6 material to a light-emitting diode in sub-millimeters. It was found that it can emit infrared light and its quantum efficiency is no less than that of visible light. It can also be applied to miniature infrared light-emitting diodes as one of the strategies for treating Alzheimer's disease.

並列關鍵字

Cs4PbI6 ； perovskite ； near-infrared light-emitting diode

參考文獻

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