Planarity Engineering of 4,5,9,10‐Pyrene Diimide ( PyDI )‐Based Semiconducting Triads Decorated with Naphthothiophene Imide ( NTI ) for Regulating n‐Type Charge Carrier Mobility

Abstract

Planarity engineering plays a crucial role in optimizing molecular packing and charge transport in OFETs. Here, four 4,5,9,10‐pyrene diimide (PyDI)‐based semiconducting triads were innovatively designed and synthesized, collectively denoted as PyDIs (PyDI‐BNTI, PyDI‐BMd‐BNTI, PyDI‐BPz‐BNTI, and PyDI‐BBTz‐BNTI). By selecting specific naphtho[2,3‐ b ]thiophene diimide (NTI) end groups and introducing various π‐bridges, we precisely modulated the planarity and molecular orbital energy levels of the molecules. DFT calculations on the triads show that the enhanced planarity lowers the calculated LUMO energy levels to −3.54 to −3.61 eV and strengthens intermolecular π‐π interactions, while electrochemical measurements reveal LUMO energy levels approaching −4.0 eV, facilitating electron transport. The four triads exhibit unipolar electron transport characteristics in solution‐processed BGTC OFETs under ambient conditions. The electron mobility increases dramatically from 6.4 × 10 ‐4 cm 2 ·V ‐1 ·s ‐1 for the twisted PyDI‐BNTI to 0.10 cm 2 ·V ‐1 ·s ‐1 for the fully planar PyDI‐BBTz‐BNTI. X‐ray diffraction (XRD) and atomic force microscopy (AFM) analyses reveal that the improved planarity leads to tighter molecular packing and more ordered crystal structures, further enhancing charge transport efficiency. This study highlights the potential of the 4,5,9,10‐pyrene diimide framework as a versatile building block for high‐performance organic electronics, providing an effective molecular design strategy to overcome the limitations of traditional n‐type semiconductors.