Crystal Structural Change of Poly(3-Alkylthiophene) Induced by Iodine Doping as Revealed by X-Ray Diffraction and Infrared/Raman Spectroscopic Measurements^*

Abstract

Based on the X-ray fiber diagram, polarized infrared and Raman spectra, the crystal structural model of iodine-doped poly(3-alkylthiophene) has been proposed: polythiophene chains are displaced along the chain axis to give the tunnels extending along the b axis, in which the I- 5 ions are mainly intercalated. The resultant charge transfer between thiophene rings and iodine molecules is considered to give polaron and bipolaron with intense transition dipole moments along the chain axis, as judged from the infrared dichroism.

Linear optical properties and electronic structures of poly(3-hexylthiophene) and poly(3-hexylselenophene) crystals from first principles

“…However, the optimized interplanar distance between two PT backbones is about 3.50Å, which is shorter than that 3.77Å, obtained from experiment. [21] Furthermore, the calculated monoclinic angle β has not yet been reported by experiments.…”

“…Tashiro et al proposed various possible schematic models of rr-P3HT using computational modeling techniques. [21,22] Quite recently, a monoclinic structure of rr-P3HT with a P 2 1 /c space group was proposed by the electron diffraction measurements. [20,29] Here, there are two uncertain points related to the structural type; does crystalline rr-P3HT have an orthorhombic or monoclinic structure, and is the lattice constant a about 32Å or 16Å.…”

“…To compare the differences in stabilities between the two structures, we first constructed the crystal structures employing the experimentally determined lattice parameters observed by Tashiro et al [21,22] The lattice constant a for the type-α structure is set to be twice as large as that for type-β, and the monoclinic angle β is set to be 90…”

“…[18][19][20] Structural determinations for the Forms I of rr-P3HT (n=6) have been performed on the basis of X-ray/electron diffraction measurements. [21][22][23][24][25][26] Most papers published in the 1990's, only show schematic models and lattice constants of crystal rr-P3AT; none are about internal coordinates and space groups. [18,21,22,27,28] In recent years, a monoclinic structure of rr-P3HT with a P 2 1 /c space group was proposed by small angle electron diffraction measurements.…”

“…[21][22][23][24][25][26] Most papers published in the 1990's, only show schematic models and lattice constants of crystal rr-P3AT; none are about internal coordinates and space groups. [18,21,22,27,28] In recent years, a monoclinic structure of rr-P3HT with a P 2 1 /c space group was proposed by small angle electron diffraction measurements. [20,29] To determine the stable crystal structure, several groups examined first-principles density functional theory (DFT) calculations, and discussed their structural properties.…”