Liquid Crystalline Perylene Diimides:  Architecture and Charge Carrier Mobilities

Abstract

The phase behavior of three N-alkyl-substituted perylene diimide derivatives is examined by differential scanning calorimetry and polarized optical microscopy. The occurrence of multiple phase transitions indicates several crystalline and several liquid crystalline phases. X-ray diffraction measurements show that the liquid crystalline phases display high structural ordering in all three dimensions: smectic layers are formed, and within these smectic layers an additional ordering in columns is observed. Molecular modeling confirms this result and substantiates smectic ordering with interdigitating alkyl chains that determine the distance between the smectic layers. The ordering in columns is favored by π-π interactions between the cofacially oriented perylene molecules and by the elliptic shape of the molecule. Finally, intermolecular dipole-dipole interactions between the carbonyl groups of the imide moieties cause the perylene molecules to orient on average with a slight rotation between neighboring molecules within a columnar stack. Following the determination of the electronic transition dipole moment, this orientation, which still involves substantial π-π interactions, could be confirmed by UV/vis spectroscopy of perylene aggregates. To gauge the potential of these materials as organic semiconductors, the charge carrier mobility of one of the perylene derivatives has been measured by pulse-radiolysis time-resolved microwave conductivity. A value in excess of 0.1 cm 2 V -1 s -1 is found in the liquid crystalline phase, and a value in excess of 0.2 cm 2 V -1 s -1 is found for the crystalline phase. These values are comparable with the highest values previously found for other discotic materials.

Thermal treatment effects on N-alkyl perylene diimide thin-film transistors with different alkyl chain

“…According to the literatures, the peaks near 140-160°C of DSC data represent the phase transition of PTCDIs between two crystalline phases. 54 These data show us that the phase transition temperature of PTCDIs is shifted to lower temperature as increasing the alkyl chain length, from 156.8°C for C12 to 136.1°C for C18, which is a general phenomenon in alkyl chain substituted molecules. [54][55][56] The long alkyl substituents add highly mobile nature to a rigid perylene skeleton.…”

“…54 These data show us that the phase transition temperature of PTCDIs is shifted to lower temperature as increasing the alkyl chain length, from 156.8°C for C12 to 136.1°C for C18, which is a general phenomenon in alkyl chain substituted molecules. [54][55][56] The long alkyl substituents add highly mobile nature to a rigid perylene skeleton. As the alkyl chain length become longer the mobile nature of molecules becomes stronger, 57,58 which results in the phase transition temperature shift to lower temperature.…”

Characterization of New Materials for Photovoltaic Thin Films: Aggregation Phenomena in Self-Assembled Perylene-Based Diimides

“…X-ray Structural Information. PE-surf systems The chemical structures ofC 12 -PDI+ and PA-are shown based on more conventional surfactants and similar in Figure 1. C 12 -PDI+ is related to several previously polyelectrolytes exhibit a diversity of morphological studied perylene diimides.…”

“…They also indicate that the long Incident Polarization (deg) molecular axes of the C 12 -PDI+ chromophores in these Figure 7. (A) and (B) MPEFM fluorescence images recorded regions are tilted off the sample normal (i.e., they have using the two different excitation polarizations shown for C 12 a component parallel to the film plane). Again, in the model PDI+/PA-thin films.…”

Organic Thin Film Photovoltaic Devices from Discotic Materials

“…4E). Perylene dfunides are known to possess high electron mobilities [32] and have been utilised previously as an electron acceptor and transport material in dye/polymer devices [33].…”