Carbazole/triphenylamine-functionalized phenanthro[4,5-abc]phenazines: Synthesis and luminescence properties

Two phenanthro[4,5-abc]phenazine derivatives, 11-(3,6-di-tert-butyl-9H-carbazol-9-yl)phenanthro[4,5-abc]phenazine (PyQ-Cz) and 4-(phenanthro[4,5-abc]phenazin-11-yl)-N,N-diphenylaniline (PyQ-TPA), were synthesized by grafting the an electron-donating carbazole and triphenylamine segments onto the pyrene-fused quinoxaline (PyQ) core, respectively and characterized by NMR (1H and 13C) and high resolution mass spectrometry. Their thermal, photophysical and electrochemical properties were systematically investigated. These compounds exhibited excellent thermal stability and intense yellow emission and orange emission in dichloromethane solution, whereas they exhibited green emission in solid films. Based on their high photoluminescence quantum yields and the frontier orbital energies, the doped devices with a structure of ITO/PEDOT:PSS (30 nm)/CBP:PyQ derivatives (x wt%) (25 nm)/TPBi (35 nm)/Liq (2 nm)/Al (150 nm) were fabricated by solution-processed the emitting layers to investigate their electroluminescence (EL) performances, in which the doped devices of PyQ-Cz exhibited the maximum external quantum efficiency (EQEmax) of 1.86%, while the PyQ-TPA doped devices showed an EQEmax of 0.82%.