The Charge Transport Anisotropy in MEHPPV (poly(2-methoxy-5-(2’-ethylhexykoxy)-1,4-phenylene vinylene) Devices

• Main Authors: Zhan-Wei Chang, 張展瑋
• Other Authors: 范文祥
• Format: Others
• Language: en_US
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/73703243743470607474

碩士 === 國立臺灣大學 === 高分子科學與工程學研究所 === 95 === The hole mobility in vertical and horizontal directions were measured by means of time-resolved or transient electroluminescence (TrEL) and field-effect transistor (FET) methods for poly(2-methoxy-5-(2’-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV). The optical properties and morphology were studied for understanding the optical and morphological effects on charge transport properties. MEH-PPV films prepared from chlorobenzene (CB) and toluene (TL) were used and fabricated into devices in this work. The results indicted the optical properties are identical but different in hole mobility. In addition, the charge mobility shows obvious difference in vertical and horizontal direction. Further, the morphological effect in conjugated polymer films was induced by using different solvents. Through scattering measurements, the solvent induced layered structure within polymer films spun from chlorobenzene (CB) solution is more predominant, however, the films spun from toluene (TL) solution show weak layered feature. Comparing morphological effects with the hole transporting results measured by thin film transistor device (horizontal direction) and polymer light emitting diode (PLED) based time resolved electroluminescence method (vertical direction), charge transport anisotropy was observed as a result of the layered structure in the conjugated polymer. Amazingly, this structural anisotropy corresponds with the mobility anisotropy and it is believed to be consistent with hole carriers owning greater mobility in the regions of high electron density which is parallel to the substrate.