CdxZn1-xSe 量子點之合成與其發光元件應用

Abstract

在本篇論文，我們利用熱注射合成法合成CdxZn1-xSe三元合金量子點，並且討論其光學特性和微結構，最後將量子點應用在發光元件上面。在合成的過程中，藉由調整octadecene和oleylamine的比例，可以獲得具不同粒徑大小的量子點和較佳的發光特性。我們發現oleylamine的使用量對於量子點的發光波段和粒徑大小有舉足輕重的影響，oleylamine的使用量增加時，量子點的粒徑從14.2 nm縮小到6.7 nm，而量子點的發光波長則從621 nm藍位移到525 nm。

因為Se對Cd和Zn的反應性不同，我們利用此特性，合成出一個富含CdSe的核心、而外殼是ZnSe的核殼結構量子點。我們將benzoyl peroxide作為一個蝕刻的藥品，將此具核殼結構的量子點進行蝕刻實驗，當量子點經過benzoyl peroxide的處理後，量子點的螢光量子產率開始下降，但是發光波段並沒有任何變動，此現象暗示著ZnSe的外殼已經被蝕刻，如此一來會降低核心的CdxZn1-xSe螢光發光強度，此結果更加可以證明所合成的量子點是一個以核心為CdxZn1-xSe，而外殼為ZnSe成份的核殼結構。

最後，我們將合成的量子點當作發光層，應用在發光元件上面。經由供給一個適當的外加偏壓，量子點發光元件可以發出範圍甚廣的顏色波段。此結果展現了本研究所開發的合成程序的優點，亦即所獲得的量子點產物能進一步被運用在電致發光的元件上，來發出高亮度的顏色且廣闊的波段。

In this work, we synthesized ternary alloyed CdxZn1-xSe quantum dots (QDs) with the hot-injection method, discussed the resultant optical characteristics and microstructures, and investigated their applications as light emitting devices. The ratio of octadecene to oleylamine employed in synthesis was modulated to obtain QDs with different sizes and satisfactory performance. It was found that QDs’ emission and size were dependent on the amount of oleylamine used. With increasing oleylamine amount, the QDs’ size was decreased from 14.2 to 6.7 nm, while their emission wavelength was blue-shifted from 621 to 525 nm.

Because of the difference in reactivity between Cd/Se and Zn/Se, a core-shell structure in which CdSe was rich in core and ZnSe comprised the shell was observed in the as-synthesized QDs. The core-shell structure of QDs was revealed with the etching experiment by using benzoyl peroxide as the etching reagent. As QDs were treated with benzoyl peroxide, the corresponding quantum yield was decreased whereas their emission wavelength did not change, implying that the shell of ZnSe was etched to depress the photoluminescence of the core of CdxZn1-xSe. This outcome provided a solid proof that the as-obtained QDs had the core-shell structure of CdxZn1-xSe-ZnSe.

At last, we applied QD products as active layer in the light emitting devices. With an appropriate external bias, the QD-emitting device could emit a wide range of colors. This result demonstrates the advantage of using the present synthetic route to obtain various QD products that may emit bright colors in their light emitting diode prototypes.