為了製作演色性較高的白光LED，將黃色螢光粉混合紅色螢光粉並結合藍光LED為一可行的方式，因此本研究試圖在常壓下利用固態反應法合成適用於藍光激發的氮氧化物CaSi2O2N2:Eu2+與氮化物Ca2Si5N8:Eu2+螢光粉。此兩種螢光粉的放射峰分別在560及608 nm，且具有良好的熱穩定性(T50至少大於160℃)，在450 nm激發下，最佳化Ca0.63Si2O2N2:0.37Eu2+螢光粉與最佳化Ca1.97Si5N8:0.03Eu2+螢光粉的外部量子效率分別為30.83%與24.02%，因此，此兩種螢光粉皆適合應用在藍光LED，此外，由於此兩種螢光粉均具有寬廣的激發光譜(300~520 nm)，所以也可以應用在近紫外LED。
其中CaSi2O2N2:Eu2+螢光粉由於Eu2+之摻雜，使得晶格擴張，產生微結構改變，相對提高Eu2+在主體中之濃度淬滅點，放光強度不斷上升直至37 mol%出現最大值，而此時已達到Eu2+在主體中的最高固態溶解度，當摻雜濃度再上升，結構開始些微崩解，單位晶胞之體積變小，在這樣狀況下Eu2+濃度處於過飽和狀態，使濃度淬滅開始形成，放光強度下降。而因為此晶格變化，使得CaSi2O2N2主體相較於其它氮氧化物主體能夠允許較多的Eu2+摻雜量，經由量測，高摻雜濃度(37 mol%)的CaSi2O2N2:Eu2+螢光粉之外部量子效率為低摻雜濃度(5 mol%)者的2.47倍，其大大的提升在LED上的應用性。
將上述所合成的螢光粉應用在藍光LED上製作白光LED，並探討不同的螢光粉塗佈結構、遠距式塗佈結構及材料折射率對白光LED光學特性的影響，實驗結果顯示在350 mA驅動下，使用Y down/ R up Type (黃色螢光粉層在下，紅色螢光粉層在上)之螢光粉塗佈結構，及Step index (漸進式折射率)作為遠距式塗佈結構之白光LED的照明效率及光功率較使用Mixed Type (黃色、紅色螢光粉混和)之螢光粉塗佈結構及Silicone gel作為遠距式塗佈結構之白光LED分別提升20%及21.4%，其白光LED之照明效率、光功率、色度座標、色溫及演色性分別為32.58 lm/W、146.19 mW、(0.3217, 0.2704)、6401 K及78。

It was known that the combination of blue light-emitting diodes (LEDs) and the mixture of yellow and red phosphors was an alternative way to fabricate a phosphor-converted white LED (pc-WLED) with the high color rendering index (CRI). In this study, we sought to synthesize CaSi2O2N2:Eu2+ and Ca2Si5N8:Eu2+ phosphors which could be well excited by blue lights by the solid-state reaction under normal atmosphere. The main emission bands of CaSi2O2N2:Eu2+ and Ca2Si5N8:Eu2+ phosphors were located at 560 and 608 nm, respectively. Besides, they also exhibited the good thermal stability with T50 at ＞160℃. The external quantum efficiency of optimized Ca0.63Si2O2N2:0.37Eu2+ and optimized Ca1.97Si5N8:0.03Eu2+ were 30.83% and 24.02% under 450-nm excitation, respectively. Accordingly, both CaSi2O2N2:Eu2+ and Ca2Si5N8:Eu2+ phosphors showed the potential to be applied on the blue LEDs. Furthermore, their excitation spectra in a broad range of 300-520 nm indicated that these phosphors could also be applied on the pc-WLEDs with the near-UV LEDs.
The host lattice of CaSi2O2N2:Eu2+ phosphors would expand because of the substitution of Ca2+ by Eu2+ ions, which lead to the change of micro-structure. Therefore, the concentration quenching point could be enhanced, and the emission intensity reached a maximum at 37 mol% where the solid solubility of Eu2+ ions was saturated. With a further increase in the Eu2+ doping level, the crystal structure started to disintegrate and the volume of the unit cell decreased, which caused the supersaturation of Eu2+ concentration; therefore, the concentration quenching occurred and the emission intensity began to decrease. Due to the said variation of the lattice, the CaSi2O2N2 host could allow more amount of Eu2+ doping than that of other oxynitride hosts, indicating the possibility of higher emission intensity. As a result, the external quantum efficiency of the high-doping sample (37 mol%) was 2.47 times than that of the low-doping sample (5 mol%). Such an eye-catching improvement significantly enhanced the feasibility of this phosphor for application to the pc-WLEDs.
The pc-WLEDs were fabricated by the blue LED chips, Ca0.63Si2O2N2:0.37Eu2+ and Ca1.97Si5N8:0.03Eu2+ phosphors. The effects of phosphor configurations and the reflective index of remote layers on optical characteristics of pc-WLEDs were investigated. Under 350 mA, the results demonstrated that the luminous efficiency and luminous power of pc-WLEDs utilizing the Y down/ R up type (red phosphor layer was above yellow phosphor layer) phosphor configuration and the step index (step-refractive index) remote configuration were 20% and 21.4% respectively higher than those of pc-WLEDs utilizing the Mixed Type (red and yellow phosphors mixed together) phosphor configuration and the silicone gel as remote layers. The luminous efficiency, luminous power, C.I.E. coordinates, correlated color temperature (CCT), and CRI of the former pc-WLED were 32.58 lm/W, 146.19 mW, (0.3217, 0.2704), 6401 K, and 78, respectively.

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