Substituent effects on the luminescence and charge transport properties of novel bis-lactam-based molecules

A series of bis-lactam-based molecules were synthesized and applied in organic field-effect transistors (OFETs) and organic light-emitting diodes (OLEDs). Among the derivatives, 1,5-dioctyl-3,7-bis(9-phenyl-9H-carbazol-2-yl)-1,5-naphthyridine-2,6-dione (NTD-pCz) exhibited the highest maximum hole mobility of 0.11 cm2 V−1 s−1, with on–off current ratios (Ion/Ioff) of >105 in OFETs, which was attributed to NTD-pCz exhibiting the lowest reorganization energy, extended π-conjugation with a relatively small dihedral angle between the NTD core and the side group, and the strongest intermolecular interaction in the thin-film state. In addition, NTD-pCz exhibited the highest maximum external quantum efficiency of 3.56%, with a current efficiency of 9.95 cd A−1, when incorporated into nondoped OLEDs, which is ascribed to its excellent solid-state photoluminescence quantum yield of 83%. These results reveal the potential of NTD-based molecules for use in efficient next-generation multifunctional optoelectronic devices.