Preparation And Structure Researching Of Poly (3-hexylthiophene) Oriented Film

As the information era has come, the demand of semiconductorbecomes larger and larger. Most of the traditional semiconductors areinorganic semiconductors which have quite good performance. However,the disadvantages of high production cost and severe environmentcontamination also limit the application of inorganic semiconductors. Asa new kind of semiconductor, organic semiconductors have lots ofadvantages compared to inorganic semiconductors, such as light weight,soft, easy to obtain and modify, and so on. Because of its high optical andelectrical characteristic, poly (3-hexylthiophene)(P3HT) attracts the mostattention in organic semiconductors researching.In this thesis, we focused on the preparation and structureresearching of P3HT oriented film. The main content includes four partsshown as follows:1. Morphology and structure of P3HT filmThe performance of P3HT film is closely related to the morphology and structure of the film. In order to obtain P3HT film with goodmorphology and structure, the conditions of film-forming and follow-uptreatments were studied. With the help of acetonitrile vapor, P3HTuniform film was obtained. And after annealed in THF vapor at differenttemperatures, many P3HT dendritic crystals and nanowire crystalsappeared in the film. The a-axis of crystal unit cell was found to beoriented out of plane in both of dendritic crystals and nanowire crystals.The growth conditions of dendritic crystals were also discussed in orderto control the number and size of the crystals.2. Morphology and structure of P3HT friction-transferred filmThe orientation of P3HT molecular chain in film can improve theoverlap of π electrons between different chains, which is very importantfor the migration of charger carrier. High molecular weight P3HToriented film was obtained by friction transfer technique. The molecularchain of P3HT was found to be oriented along the rubbing direction andthe b-axis of crystal unit cell was perpendicular to the film surface.However, because the shear force was focused on the interface betweensubstrate and P3HT film, the orientation in the bottom of the film is betterthan that on surface. Several methods were tried to improve theorientation of P3HT friction-transferred film, such as self-seedingcrystallization, heat annealing and vapor annealing. It was found thatTHF vapor can improve the surface orientation of the film without destroying the inner oriented structure.3. Epitaxial crystallization of P3HT on highly oriented PE substrateAlthough the orientation of P3HT friction-transferred film can beimproved by follow-up treatments, the spatial arrangement of backbonechain plane is not good for charger carriers to migrate in the film. Highlyoriented P3HT film with large area was obtained by epitaxial crystallizedon highly oriented PE film. The molecular chains of P3HT and PE wereparallel to each other, and the b-axis of P3HT crystal unit cell wasoriented in film plane. The epitaxial relationship between P3HT and PEcrystals was also revealed.4. Defects in PE-39-propyl single crystalThere are always some defects in polymer crystals, and these defectswill affect the spatial arrangement of molecular chains in crystals. As thesubstrate of P3HT epitaxial crystallization, the crystal structure anddefects of PE crystals also have impact on the growth of P3HT crystals.The crystal structure and defects in PE-39-propyl single crystal werestudied. Crystal structure defects were observed in PE-39-propyl singlecrystal by STEM. The defects were attributed to the inclusion of sidechains in crystal. As the results of crystal defects, both of the meltingtemperature and lamellae thickness of PE-39-propyl reduced and thelattice constants also changed. According to the electron diffractionpatterns, the arrangement of defects in crystal was simulated. Besides, the strange polycrystalline diffraction patterns, which look like the DPs offibrous crystals, were also obsearved and explained.