藉陽離子取代調控近紅外光螢光粉之放光特性

Abstract

近年來，近紅外光源之應用日益蓬勃發展，然因傳統白熾燈與鹵素燈效率低、便攜性低、工作溫度高等劣勢，促使螢光粉轉換發光二極體(phosphor-converted light-emitting diodes; pc-LEDs) 之需求增加，故優化近紅外光螢光粉並將其利用於光源為首要發展目標。 本研究第一部分著重於寬化近紅外光一區Ga2–x(Al0.68In0.32)xO3:Cr3+螢光粉放射光譜。藉(Al0.68In0.32)3+比例之陽離子取代主結構Ga2O3中半徑相同之Ga3+陽離子，增加結構中之亂度以提升電子–聲子耦合效應，使結構中Cr3+放射光譜增寬。於摻雜量達x = 0.8時，可得放射光譜涵蓋近紅外光一區650–1000 nm波段，且半高寬增寬30%達148 nm，同時維持內部量子效率約80%，並於LED封裝測試藉350 mA之驅動電流下得68.8 mW之輸出功率。 本研究第二部分專注於提升近紅外光二區Mg1–yGa2–xO4:xCr3+,yNi2+螢光粉之放光效率。此系統藉部分尖晶石結構與共摻雜活化劑之能量轉移概念，欲將藍光LED能量自Cr3+之吸收轉移至Ni2+之放光系統並放射二區近紅外光。於調控Cr3+濃度時揭示Cr3+團簇之產生，且其可大幅提升Cr3+與Ni2+間之能量轉移效率，優化後得其放射光譜涵蓋近紅外光二區1000–1650 nm波段，並可得高達97%之放光效率，為現今文獻中最高紀錄。 本研究之新穎性為藉陽離子取代法優化近紅外光螢光粉，此方法於第一部分寬化放射光譜，於第二部分提升放光效率，並於合成後以結構精修等結構鑑定方法探討其對於配位環境與放光性質之影響，最終藉LED進行封裝測試並證實其於應用層面之潛力。

The application of near-infrared (NIR) light sources has been increasingly popular recently, which has led to an increase in demand for phosphor-converted light-emitting diodes (pc-LEDs). Therefore, the primary goal is to optimize the NIR phosphors. The first part of this study focuses on broadening the emission spectrum of Ga2–x(Al0.68In0.32)xO3:Cr3+ phosphors in the NIR-I region. By substituting the cation Ga3+ in the main structure of Ga2O3 with the same radius cation (Al0.68In0.32)3+ to increase the disorder in the structure and enhance the electron–phonon coupling effect, the emission spectrum of Cr3+ in the structure is broadened. At the highest concentration of substitution, the emission spectrum covers the NIR-I region of 650–1000 nm with a 30% increase in the full width at half-maximum to 148 nm, while maintaining an internal quantum efficiency (IQE) of about 80%. Furthermore, under the condition of 350 mA current in LED packaging testing, an output power of 68.8 mW can be obtained. The second part of this study aims to improve the IQE of Mg1–yGa2–xO4:xCr3+,yNi2+ phosphor that emits light in the NIR-II region. This system uses the energy transfer (ET) concept in intermediate spinel structure by co-doping activators, resulting in emission in the NIR-II region. When adjusting the concentration of Cr3+, Cr3+ clusters were found to be induced, which can significantly enhance the ET efficiency between Cr3+ and Ni2+. After optimization, the radiative spectrum covers the NIR-II region with an IQE up to 97% can be obtained, which is the highest record in the works of literature. This study investigates the effects of the changed coordination environment and luminescent properties of synthesized samples by cation substitution and studies the luminescent mechanism along with a demonstration of practical application.