Growth of Pentacene-Doped p-Terphenyl Crystals by Vertical Bridgman Technique and Doping Effect on Their Characterization

Abstract

High quality pentacene-doped p-terphenyl crystals were successfully grown by the modified vertical Bridgman technique with a specially designed double-walled ampule. Upon the dopant addition, the growth crystal exhibits a color change from colorless to purple due to the guest-induced absorption changes. Powder X-ray diffraction, Fourier transform infrared (FTIR), 1H nuclear magnetic resonance (NMR), and fluorescence spectra studies of the doped crystal were carried out and compared with those of a pure p-terphenyl crystal. The decrease in both crystallinity and fluorescent intensity of the doped crystal clearly indicates that the guest molecules appear as defects in the form of irregularly oriented molecules which do not significantly distort the crystal structures. No significant changes on FTIR and 1H NMR spectral features of the doped crystal in relation to the corresponding features observed for the single crystal shows that the crystal doping in such small amounts does not lead to noticeable changes ...