Enhancement of molecular-level ordering of isoindigo based organic materials through deprotecting of cleavable carbamate groups with long alkyl chains

Abstract

A new highly soluble isoindigo based organic material with both cleavable carbamate protecting groups bearing long alkyl chains and thiophene groups was successfully synthesized. The carbamate protecting groups were easily removed by solvent-vapor thermal annealing using a mixture of trifluoroacetic acid and chloroform. Deprotection of the NH functional groups in the isoindigo backbone in situ facilitated H-bonding that dramatically improved the strength of the intermolecular interactions. X-ray diffraction and high-voltage electron microscopy studies of the resulting organic material showed long-range ordered crystalline structure. High crystallinity due to enhanced π-π stacking and hydrogen bonding significantly improved the charge carrier mobility. The hole mobilities of isoindigo based organic material measured by SCLC method improved from 3.46 x 10−6 cm2 V−1 s−1 to 1.13 x 10-3 cm2 V−1 s−1 upon deprotection of the NH functional groups. © 2018 Elsevier B.V.