調節施加電壓脈衝週期對於 主客體白光電化學元件電致發光光譜的影響

Effects of Tuning the Applied Voltage Pulse Periods on the Electroluminescence Spectra of Host-Guest White Light-Emitting Electrochemical Cells

吳明倫(Ming-Lun Wu)

指導教授 ： 蘇海清

國立交通大學/光電學院/光電系統研究所/碩士(2018年)

摘要

固態發光有機電化學元件具有簡單的元件構造、低操作電壓與安定的注入陰極金屬等優點。現今智慧照明發跡，光色的變化需求更顯得重要。在此研究中，將追尋一個創新的方式來達到改變固態發光元件光色的需求。利用脈衝電壓驅動白光固態照明元件，並且調整週期來改變光色。在短週期下，元件無法被完整充電，使得有效電場較低，在主客體摻雜之下，客體發光較明顯，因此得到較紅的光色與較低的色溫。在長週期的脈衝電壓驅動下，元件較能完整的充電，因而得到較藍的光色與較高的色溫。在定電壓驅動下，色溫提高將伴隨亮度的大幅增強，本實驗提出以脈衝電壓驅動白光電化學元件，提供靜置時間，可讓元件維持在相似的亮度下得到不同的色溫。週期調整的範圍為 0.2 到 20毫秒，由頻譜可得到色溫變化由2482 到5723 K，可有效的達到照明需求。此改變光色的創新方法不需要外加光學元件，即可達到隨時調變色溫的效果，極具照明用途的應用潛力。

關鍵字

有機電化學元件 ； 脈衝電壓調控 ； 固態發光

並列摘要

Solid-state white light-emitting electrochemical cells (LECs) are potential candidates in solid-state lighting due to their promising advantages of simple device structure, low-voltage operation and compatibility with inert cathode metals. Adjusting the correlated color temperature (CCT) of background illumination is highly desired for modern smart lighting systems. In this work, a novel technique to tune the CCT of EL from white LECs is proposed. The white LECs are driven by voltage pulses and color tuning is achieved by simply adjusting the voltage pulse period. A shorter voltage pulse period is insufficient to completely charge the capacitive LEC device and thus the average voltage applied on the device is lower. Since the energy level offsets of the host and guest molecules induce carrier trapping, lower average applied voltage results in more pronounced guest emission. Therefore, reddish white EL with a lower CCT can be obtained. On the other hand, a longer voltage pulse period facilitates more complete charging and the average voltage applied on the white LEC is higher, rendering bluish white EL with a higher CCT. By tuning the voltage pulse period from 0.2 to 20 ms, the CCT of EL from white LECs ranges from 2482 to 5723 K. The CCT range is sufficient for general lighting applications. In contrast to color tuning of white LECs under constant-voltage driving, in which > 10X brightness enhancement is accompanied by higher-CCT white EL, the discharging half-period in pulse-voltage driving provides relaxation time to turn off the device and reduces average brightness of the white LECs driven under a longer voltage pulse period. Therefore, similar brightness can be achieved for white EL with different CCT. No additional optical filtering device is needed for this novel color tuning technique and it is potential for use in solid-state lighting applications.

並列關鍵字

light-emitting electrochemical cells ； pulse-voltage driving ； solid-state lighting

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