Polymorphs of Pentacene and 6,13-Pentacenequinone in Solution and Vapor Phase Growths

A new polymorph of PQ-S was demonstrated for the first time. This polymorph was grown in solution through the oxidation of PEN, creating a zigzag structure that was tilted by 21 .deg. with respected to a-axis. The PQ-V crystal had a packing structure similar to a thin-film phase, where oxygen was a critical factor in determining the molecular packing. The remarkable shift in the PL maximum wavelength between PQ-S and PQ-V of up to 30 nm confirmed that the molecular packing difference strongly influenced the light emitting properties. The structural changes from pentacene to pentacenequinone that occured through oxidation were carefully studied in the single crystal analysis and provided useful information on the quality and performance of the pentacene-containing devices. This present study on the polymorph of pentacene and pentacene-quinone provides some basic structural data. Conjugated organic compound thin films have received considerable attention because of their great potentials in thin-film transistors, light emitting diodes and photovoltaic cells. The investigation of organic materials with large charge carrier mobilities has recently become the main research interest in semiconductors. One of the most interesting organic semiconductor materials is pentacene (PEN), which exhibits a remarkably high charge carrier mobility (≥ 1 cm²V^-1s^-1), despite being composed of molecular crystals with a relatively weak van der Waals interaction between the molecules