發光二極體用之活化中心控制螢光材料研發

Activator Controlled Phosphors for Light-emitting Diodes

黃冠維(Kuan-Wei Huang)

指導教授 ： 劉如熹

國立臺灣大學/理學院/化學研究所/碩士(2012年)

https://doi.org/10.6342/NTU.2012.10907

摘要

白光發光二極體具高發光效率、壽命長、低汙染、體積小等優點，使其近年來備受矚目，而成為二十一世紀照明之曙光。因白光發光二極體係以藍光或紫外光發光二極體晶片激發螢光粉而形成白光，故開發適合發光二極體用之螢光粉為當前重要課題。
　　因目前新型螢光粉開發多採嘗試錯誤方法，摻入之活化劑Eu若以Eu3+形式存在，其線光譜特性相對Eu2+之應用性較低，故本研究第一部分係提出利用晶格結構調變方法以開發螢光粉，並施行於新型螢光粉主體Ca12Al14O32F2:Eu，其乃藉由Si4+-O2-摻入晶格取代Al4+-F-，以調控活化中心格位，進而使原難以還原之Eu3+離子漸轉換為Eu2+而產生寬帶光譜放光，並藉由粉末繞射結構精算其晶格變化機制，輔以固態核磁共振光譜、X光吸收光譜佐證光激光譜現象，確立此法可藉調變活化中心格位以開發新型螢光粉主體。
　　本研究第二部分乃為開發新系列螢光粉主體：Li5La3M2O12:Ln3+ (M = Nb, Ta; Ln = Pr, Sm)，利用結構精算其不同活化劑摻入之晶格變化，並以低溫變溫光譜及時間解析光譜探討Pr3+之能階放光機制，提出其躍遷機制，鐠摻雜之粉體放光屬多帶光譜，其於藍綠光及紅色波段皆具放光，其可應用於藍光發光二極體，而釤摻雜之粉體於紫外光激發下可放紅光，具應用潛力。

關鍵字

螢光粉 ； 固態照明 ； 固態反應 ； 結構精算 ； 發光二極體

並列摘要

Light-emitting diodes (LEDs) have received wide attention in the recent decade owing to their high brightness, long lifetime, environmental friendliness and small size. The conventional means of generating white light in white LEDs combine of phosphor layer with UV- or blue-LEDs that converts the initial radiation into a complementary color. The development of new phosphor is of priority concern in LED-driven applications.
The development of new phosphor is limited in try-and-error method. When the incorporation Eu exist in Eu3+ state, comparing the broad band photoluminescence in Eu2+, the line emissions in Eu3+ activated phosphor is less applicable for LED-pumped white light. In this study, we therefore provide a crystal based method approach for developing phosphors. The proposed approach is successful demonstrated in the new phosphor Ca12Al14O32F2:Eu3+. By using of Si4+–O2- to replace Al3+–F- and Eu3+ is therefore able to reduce to Eu2+, which can provide broadband emissions. Combinatorial studies with synchrotron X-ray diffracrion (XRD) refinement, X-ray absorption near-edge structure (XANES), high resolution electron microscope (HRTEM) and solid state nuclear mangetic resonance (NMR) help to understand how the dopant affects the crystal structure and photoluminescence. The results were agreed well with the proposed mechanism of crystal variation in our study.　
We also report a novel phosphor series Li5La3M2O12:Re3+ (M = Nb, Ta; Re = Pr, Sm). The XRD refinement is adopted to characterize the variation of lattice. Based on the results of low temperature photoluminescence measurement and time-resolved spectrum, the transition mechanism of Pr3+ analogue is therefore proposed. The Pr3+ analogue exhibits multiband emission within bluish-green and red range, and can serve as a candidate for blue-LED. In addition, the Sm3+ analogue exhibits red luminescence upon UV light excitation, showing that can apply in UV-LED related applications.

並列關鍵字

phosphors ； solid state lighting ； solid state reaction ； refinement ； light emitting diodes

參考文獻

42. 陳振中，固態核磁共振光譜圖簡介，2006。

9. Gernot Hoffman, CIE Color Space. http://www.fho-emden.de/~hoffmann/ciexyz29082000.pdf

23. Huang, C. H.; Liu, W. R.; Chen, T. M. J. Phys. Chem. C 2010, 114,

63. Kim, T. G.; Lee, H. S.; Lin, C. C.; Kim, T.; Liu, R. S.; Chan, T. S.; Im, S. J. Appl. Phys. Lett. 2010, 96, 061904..

45. Huang, C. H.; Wu, P. J.; Lee, J. F.; Chen, T. M. J. Mater. Chem. 2011, 21, 10489.