Supramolecular Self-Assembly of Diketopyrrolopyrrole with Unprecedented Photoconductivity

The oscillation of chemical bonds in molecular semiconductors plays a key role in fragmenting the electric conducting pathways due to the large fraction of free volumes, acting as "trap sites" for charge carriers. Incorporating directional noncovalent chemical bonds between the monomeric unit in organic semiconductors is an excellent approach to reducing thermally induced structural fluctuations, resulting in a decrease in a trap densities. In this work, we utilize noncovalent interactions in diketopyrrolopyrrole (DPP)-based supramolecular assembled systems to enhance or tune the photoconductivity and charge transport properties. Infinitesimal molecular design by substituting different side chains and introducing intramolecular dihedral angles leads to a notable difference in solid-state packing, transient photoconductivity, and thin film morphology. Grazing incidence wide-angle X-ray scattering, and thin film X-ray diffraction measurements reveal that the packing order is enhanced for hexyl substituted DPP derivatives, resulting in high intrinsic charge carrier mobility of ∑μ = 1.7 cm2 V–1 s–1. At the microscopic level, electron microscopy reveals that the unique self-assembly remarkably improves the structural order via directional hydrogen bonding. These findings exemplify that the supramolecular self-assembly strategy via hydrogen bonding networks is an efficacious way to reduce the molecular vibration and structural defects in molecular semiconductors and ameliorate the performance in optoelectronic devices.