Molecular-scale-ordered structures of isoindigo and bithiophene-based small molecules through hydrogen bonding

Abstract

The synthesis of molecular-scale-ordered isoindigo and bithiophene-based small molecules has been achieved through hydrogen bonding by using ethylenediamine (EDA) as a linking material, or by the cleavage of the carbamate protecting groups bearing long alkyl chains. X-Ray diffraction and high-voltage electron microscopy (HVEM) studies show that the molecules are arranged to form body-centered cubic (BCC) or face-centered cubic (FCC) lattice structures. Formation of hydrogen-bonded networks resulted in enhanced molecular ordering that facilitated charge carrier mobility. The hole mobilities of isoindigo and bithiophene-based organic materials estimated by hole only devices enhanced from 2.42 × 10−6 cm2 V−1 s−1 to 1.23 × 10−3 cm2 V−1 s−1 for ID2T after crosslinking with ethylene diamine and from 2.79 × 10−6 cm2V−1 s−1 to 2.52 × 10−3 cm2 V−1 s−1 for NHID2TC after removing the protecting groups which are upon the formation of hydrogen bonding between molecules.