| 摘要: | 本論文主要以共軛發光高分子poly(9,9-dioctylfluorene -alt-benzothiadiazole) (F8BT)摻雜離子液體 tetradecyltrihexylphosphonium (trifluoromethylsulfonyl) amide (P66614-TFSA) 作為主動層製作平面 (planar) 與垂直 (sandwich)結構之高分子電化學發光元件(Light-emitting electrochemical cell, LEC)，藉此研究其光電特性，並比較使用高與低分子量 F8BT 之差異。
實驗上，首先透過空間電荷限制電流擬合單載子元件特性曲線，得知高與低分子量的 F8BT分別具有平衡與不平衡的電子與電洞遷移率。接著以不同分子量 F8BT 摻雜不同濃度之P66614-TFSA製作planar LEC 和 sandwich LEC。
比較所有元件表現，發現無論高或低分子量摻雜的 F8BT LEC 元件相較於未摻雜的F8BT 元件可具有較高外部量子效率。此效應在 planar 結構下尤其顯著，其中未摻雜元件不具備導電及發光之表現，而摻雜元件可大幅提升電流密度並在通道中觀察到發光的現象。以摻雜濃度為10：1的高分子量 F8BT 之planar LEC達到高的外部量子效率(約0.05%)。相較之下，以同樣摻雜濃度的低分子量 F8BT planar LEC 則具有較低的外部量子效率(0.004%)。然而無論高或低分子量 F8BT之摻雜元件，均有發光線偏向陰極的現象，推測可能是電化學副反應 (electrochemical side reaction) 的發生，使得高分子在陰極的還原反應較慢發生。
另一方面，在高與低分子量 F8BT sandwich LEC，以摻雜濃度為10：1的高分子量 F8BT 之sandwich LEC達到最高的外部量子效率(約0.02%)，同樣摻雜濃度的低分子量 F8BT sandwich LEC 則具有較低的外部量子效率(0.001%)，並透過光學顯微鏡可發現摻雜元件具有完整的發光面積，推論電子的注入效率有大幅的提升。
此實驗結果證實高分子電化學發光元件可應用於高電流密度以及低驅動電壓之有機發光元件的研究。
;In this thesis, we used of blends composed of poly(9,9-dioctylfluorene-alt-benzothiadiazole), F8BT and a ionic liquid ,tetradecyltrihexylphosphonium (trifluoromethylsulfonyl) amide (P66614-TFSA), as the active layer, in planar structure polymer light-emitting electrochemical cell (LEC) and sandwich structure LEC.We study the optic and electric property of the device,and compare the difference between using high and low molecular weight F8BT.
First,the carrier mobility of difference molecular weight F8BT at carrier only device has been estimated by using space-charge-limited current measurements in experiment.After that,we use different molecular weight of F8BT for difference doping concentration to fabricate the planar LEC and sandwich LEC.
We observe whether the high or low molecular weight F8BT doping device has higher external quantum efficiency than undoped F8BT device and in all device performance.The effect is obvious especially in planar LEC.Undoped device don’t have conductivity and emit the light among the device.However the doping device current density can increase dramatically,and observe the light in the channel.When the planar LEC is used high molecular weight F8BT for doping concentration 10：1 condition,the device can achieve high external quantum efficiency(~0.05%) in all device.By contrast,when the planar LEC is used low molecular weight F8BT for same doping concentration,the device has lower external quantum efficiency(~0.004%).However High or low molecular weight F8BT of doping device,the emission line is close to cathode. we surmise that situation is caused by electrochemical side reaction,it make polymer reduction happened slow in cathode.
On the other hand, When the sandwich LEC is used high molecular weight F8BT for doping concentration 10：1 condition,the device can achieve high external quantum efficiency(~0.02%) in all device. When the sandwich LEC is used low molecular weight F8BT for same doping concentration,the device has lower external quantum efficiency(~0.001%).We observe the doping device have whole emission area by optic microscope.we surmise the electron injection efficiency increase dramatically.
The work prove that polymer LEC apply high current density and low driving voltage to organic light emitting device investigation. |
