調控尖晶石型態螢光粉之結構與近紅外光放光特性

Abstract

近紅外光因其特殊性質，於各領域中展現巨大潛力。螢光粉轉換發光二極體為現今廣泛應用之光源，因其具可調控放射帶與放光波長、高效率、便攜帶性等優勢，造就其於近紅外光源之極大競爭力，故發展可應用於螢光粉轉換發光二極體之近紅外光螢光粉為本研究之目標。 本研究第一部分致力於研究不同尖晶石結構之近紅外光螢光粉，藉Cr3+/Ni2+共摻雜之MgAl2O4–MgGa2O4–Mg2SnO4固態溶液，探討自部分反尖晶石至正尖晶石與反尖晶石之結構轉換過程與近紅外光放光性質。此部分著重探討尖晶石結構中Cr3+團簇與Ni2+放光於結構轉換之變化，並引入能量轉換與化學壓力之概念，於拓展放光至近紅外光二區之同時，進一步調控放光波長之紅移與藍移，最終，開發相異波長之近紅外光二區光源可利用於生醫影像之應用。 本研究第二部分致力於研究Cr3+單摻雜類尖晶石結構LiGa5O8之晶體結構與近紅外光性質。藉一系列相異摻雜濃度之LiGa5–xO8:xCr3+螢光粉，探討高濃度活化劑摻雜下離子間作用力變化，除離子對與離子團簇外，離子對間之內部價電荷轉移機制被揭示為近紅外光二區放光之來源，故此部分藉結構、放光性質及機制分析探究近紅外光之生成原因。 本研究之新穎性為系統性研究不同種類之尖晶石結構，提供兩相異機制作為二區近紅外光之放光策略。第一部分藉雙摻雜活化劑進行能量轉移，第二部分藉高濃度單一摻雜活化劑促使內部價電荷轉移之躍遷。除螢光粉之合成外，藉一系列長程與短程之結構精修、放光性質鑑定、穩定性測試等，分析性能與探討機制，最終進行封裝測試揭示其應用性，證實近紅外光光源之巨大發展潛力。

Near-infrared (NIR) light has great potential in various fields due to its special properties, so it is necessary to develop an NIR light source. Phosphor-converted light-emitting diodes (pc-LED) are widely used nowadays since their advantages include adjustable emission wavelengths, high efficiency, and portability. Therefore, creating the NIR phosphor for the pc-LED application is the goal of this research. The first part of this research is devoted to developing NIR phosphors with different spinel structures. This work focuses on Cr3+/Ni2+-doped MgAl2O4–MgGa2O4–Mg2SnO4 spinel-type solid solutions to investigate the dynamic change of structure and luminescence properties. By the cation substitution strategy, the chemical pressure and energy transfer (ET) induce the tunable emission in the NIR region. Finally, the NIR pc-LED is fabricated and demonstrated as the light source for bio-image and anti-counterfeiting applications. The second part of this research is dedicated to studying the heavy Cr3+-doped spinel-like LiGa5O8 phosphor. This work focuses on investigating the relation between luminescence properties with different Cr dopant interactions. The NIR-II emission is confirmed to undergo the intervalence charge transfer (IVCT) mechanism and successfully explore the way for Cr3+ single-doped phosphor to reach the dual-emission cover in both the NIR-I and II regions. The novelty of this research is to systematically study different types of spinel structures and provide two different mechanisms as strategies for tuning NIR emission, in which the first part applies energy transfer and the second part applies intervalence charge transfer transition.