ChemPlusChem | 2019
A Solution-Processable meso-Phenyl-BODIPY-Based n-Channel Semiconductor with Enhanced Fluorescence Emission.
Abstract
The molecular design, synthesis, and characterization of an acceptor-donor-acceptor (A-D-A) semiconductor BDY-Ph-2T-Ph-BDY comprising a central phenyl-bithiophene-phenyl π-donor and BODIPY π-acceptor end-units is reported. The semiconductor shows an optical band gap of 2.32\u2005eV with a highly stabilized HOMO/LUMO (-5.74\u2005eV/-3.42\u2005eV). Single-crystal X-ray diffraction (XRD) reveals D-A dihedral angle of ca. 66° and strong intermolecular C-H\u2009⋅⋅⋅\u2009π (3.31\u2005Å) interactions. Reduced π-donor strength, increased D-A dihedral angle, and restricted intramolecular D-A rotations allows for both good fluorescence efficiency (ΦF =0.30) and n-channel OFET transport (μe =0.005\u2005cm2 /V\u2009⋅\u2009s; Ion /Ioff =104 -105 ). This indicates a much improved (6-fold) fluorescence quantum yield compared to the meso-thienyl BODIPY semiconductor BDY-4T-BDY. Photophysical studies reveal important transitions between locally excited (LE) and twisted intramolecular charge-transfer (TICT) states in solution and the solid state, which could be controlled by solvent polarity and nano-aggregation. This is the first report of such high emissive characteristics for a BODIPY-based n-channel semiconductor.