於本研究中，本團隊嘗試使用低溫(200℃)、高反應時間(24h)之水熱法，合成擁有下轉換能力之螢光粉體－YEO4(E=P或V)共摻雜鋱離子(Tb3+)與鐿離子(Yb3+)。在本實驗中，我們成功合成出了具有下轉換機制之粉體，並且在室溫環境中，透過473 nm雷射激發下，成功放出一系列Tb3+之藍綠光放光 (4D5 → 7FJ)，以及透過下轉換機制將能量透過Tb3+離子轉換到Yb3+離子上，而放出的近紅外光 (2F5/2 → 2F7/2)。首先，本團隊嘗試改變Yb3+離子之摻雜濃度，來觀察可見光區段與近紅外光區段之放光有甚麼不同。發現到通常Yb3+離子之摻雜濃度為5%時，會獲得最佳之可見光與近紅外光強度；之後，由於濃度淬減效應(concentration quenching effect)，放光強度即會隨著Yb3+離子之摻雜濃度增加而下降。接著，我們進一步透過觀察近紅外光放光強度與入射激發光源能量之關係，發現到在YEO4 (E=P或V)共摻雜鋱離子(Tb3+)與鐿離子(Yb3+)系統中，其量子切割能量轉換的機制傾向於透過中間虛擬能階(Intermediate virtual state)進行能量轉換。以上各系統，對於減少太陽能電池廢熱進而增加轉換效率有相當不錯之前瞻性。

In this research, we have successfully synthesized YEO4 (E=P or V) co-doped with Tb3+ and Yb3+ phosphor which is capable to conduct down-conversion in low temperature (200℃) and long reaction time (24h). Next, we use the 473 nm laser to excite the phosphor, then, we measure the visual emissions which come from the Tb3+ (4D5 → 7FJ) and also the NIR emissions which corresponding to the Yb3+ (2F5/2 → 2F7/2), energy transfer from the Tb3+.
Later, we try to adjust the concentration of Yb3+. The highest emission of visual and NIR are appearing as the concentration of Yb3+ is 5%. As the concentration of Yb3+ higher than 5%, the emission intensity of visual and NIR are lower, due to the concentration quenching effect.
Furthermore, we try to figure out the quantum cutting energy transfer mechanism of Tb3+-Yb3+ system co-doped in YEO4 (E=P or V) by the slope of the logarithmic dependence of 1%Tb3+, 5%Yb3+ NIR down-conversion emission intensity as a function of logarithmic of input excitation power. However, both two systems prefer to appear the energy transferring via intermediate virtual level process, where the energy transfer is from one Tb3+ ion to two Yb3+ ions mediated by a virtual level.
All the systems above are the promising materials as reducing the loss of energy in conventional solar cells and also enhancing their efficiencies.

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