| dc.description.abstract | 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. | en_US |