Synthesis, luminescence and charge transport properties of furan/phenylene co-oligomers: The study of conjugation length effect

Heteroaryl-containing co-oligomers are considered among the most promising materials for organic optoelectronics. In this work we synthesized a series of linear furan/phenylene co-oligomers (FPs) with different molecular length and studied their structure, luminescence and charge transport properties. The X-ray diffraction experiments revealed the higher distortion of molecular planarity for the longer FPs which is assigned to the crystal environment effect. All FPs demonstrated stability and high photoluminescence quantum yield (PL QY) both in solution and vapor-grown single crystals. The absolute PL QY as high as 70% was demonstrated for FP6 single crystal. The top-contact top-gate organic field-effect transistors (OFETs) demonstrated virtually the same mobility ∼0.35 cm2/Vs for a FPs with different conjugation chain. However the threshold voltage for the studied OFETs was demonstrated to be significantly reduced for a co-oligomer FP7 with longer conjugation chain. Thus we conclude that the increase of conjugation chain for co-oligomers does not benefit an increase of charge carrier mobility but improve the crystal/dielectric interface.