3:30 PM - 3:45 PM
△ [17p-B201-5] Analysis of the Molecular Orientation of Poly(3-hexylthiophene) on Silicon Treated with Silane Coupling Agents, by Infrared p-Polarized Multiple-angle Incidence Resolution Spectrometry
Keywords:molecular orientation, organic semiconductor, silane coupling agents
In organic devices such as dye-sensitized solar cells and organic light-emitting diodes (OLEDs), the molecular orientation of the organic thin film has a strong influence on device performances; thus, its control is an important subject. An effective method for controlling the molecular orientation of the organic thin film, is to control the surface condition of the substrate by subjecting the latter to surface modification such as silane coupling, UV, or plasma treatment. Therefore, for device development, it is important to know the relationship between the surface modification of the substrate and the molecular orientation of the organic thin film. Infrared p-polarized multiple-angle incidence resolution spectrometry (pMAIRS) measurements were performed for poly(3-hexylthiophene) (P3HT) on silicon treated with silane coupling agents. Two types of silane coupling agents, with different functional groups, were used; 3-aminopropyltriethoxysilane (APS) and n-octyltrichlorosilane (OTS). Analysis of the orientation angle of the thiophene ring revealed that the ring was oriented in a more perpendicular direction to the substrate in the APS-treated substrate, and a more parallel direction in the OTS-treated substrate. It appears possible that the P3HT orientation varied due to aggregation resulting from the presence of the amino group of the silane coupling agent on the substrate surface. The amino group forming the end group of the APS strongly influences the P3HT molecular orientation, causing it to shift to a more perpendicular direction with respect to the substrate.