Synthesis and properties of new triphenylamine based luminescent hole transporting materials containing naphthyl and butadiene units

Abstract

Two new triphenylamine based hole transporting materials (HTM1 and HTM2) containing naphthyl and butadiene moiety were synthesised via Witting–Horner reaction and characterised by 1H NMR, 13C NMR, Fourier transform infrared and mass spectrometry. The optical, electronic and thermal properties of HTM1 and HTM2 were studied in detail. The highest occupied molecular orbital level of HTM1 and HTM2 is −5·22 and −5·04 eV respectively. These two compounds show similar Ultraviolet–visible and photoluminescence spectra in solution of tetrahydrofuran and soiled films, which indicated that these compounds remain as an amorphous state in thin solid films. HTM1 shows strong blue green emission with high solution fluorescence quantum efficiency (0·87), suggesting that HTM1 has promising potential applied as emitting materials. The two compounds could form amorphous film by spin coasting, and no crystallisation was observed after annealing at 80°C for 24 h, indicating the capability of forming stable amorphous glassy states of HTM1 and HTM2. These results show the potential of HTM1 and HTM2 as hole transporting and light emitting materials applied in organic light emitting devices.