Enhanced Charge-Transport Property of F8BT Films with Electric-Field-Assisted Casting
Date Issued
2011
Date
2011
Author(s)
Kao, Yu-Tai
Abstract
In this study, the morphology of poly((9,9-di-n-octylfluorenyl-2,7-diyl)-alt- (benzo(2,1,3)thiadiazol-4,8-diyl)) (F8BT) were studied for understanding its effect on optical properties and carrier mobility. The morphology of films was observed by polarized optical microscope (POM) and the actions of molecules were deduced by UV-visible absorption spectra and photoluminescence (PL) spectra. The carrier mobility in horizontal direction was measured by using a field-effect transistor (FET) geometry.
Comparison of films prepared from different methods, spin-coating, drop-casting and drop-cast film at presence of a static electric field (E-drop-casting) offered an opportunity to characterize the influence of film morphology on charge transport. The films suffered heat treatments showed a nematic liquid crystalline (LC) phase and kept on through quenching resulting in red-shifted absorption spectra. Only the E-drop-cast film revealed an optical anisotropic phase viewed by POM, implying that F8BT molecules rearranged to an ordered structure under the presence of a static electric field. Furthermore, the E-drop-cast film after annealing came into the most obvious LC phase. Both the E-drop-cast films and the films after heat treatment showed the similar carrier mobility.
The results indicated that static electric field could drive F8BT polymer chains to pack with each others and generated ordered structure. The films after annealing also exhibited ordered structure in nematic liquid crystalline phase. These ordered structures enhanced the mobility approximate to one order. The advantage of preparing the film at presence of electric field could not only avoid heat treatment but also raise charge transport mobility.
Subjects
Polarized Optical Microscope
UV-visible Absorption Spectra
Field-Effect Transistor
Morphology
Nematic Liquid Crystalline phase
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-100-R96549021-1.pdf
Size
23.54 KB
Format
Adobe PDF
Checksum
(MD5):465096bb7e81b3332fb0d80ee9e97ded