Synthesis and luminescent properties of the indolo[3,2-b]carbazole derivatives containing coumarin fluorophores

Two new indolo[3,2-b]carbazole derivatives containing coumarin fluorophores (2,8-ICZ-C and 3,9-ICZ-C) were synthesized by the introduction of two 7-diethylamino-3-coumarinyl fluorophores at 2,8-positions and 3,9-positions of the indolo[3,2-b]carbazole (ICZ) core, respectively, as the organic emitters for organic light-emitting devices (OLEDs). The photophysical and electrochemical properties and thermal stabilities of the compounds were systematically investigated. These compounds exhibited good thermal stability as well as strong blue emission (Φf of 79.67 % for 2,8-ICZ-C and Φf of 55.90 % for 3,9-ICZ-C) in CH2Cl2 solution. The doped devices with a structure of ITO/PEDOT:PSS (50 nm)/2,6DCzPPy:ICZ derivative (x, wt%) (30 nm)/TPBi (20 nm)/Liq (3 nm)/Al (130 nm) were fabricated by solution-processed the emitting layers, in which the 2,8-ICZ-C device exhibited a maximum luminance (Lmax) of 1425 cd/m2, a maximum current efficiency (CEmax) of 1.24 cd/A and a maximum external quantum efficiency (EQEmax) of 0.71 %, and the 3,9-ICZ-C device showed Lmax, CEmax and EQEmax of 1005 cd/m2, 1.14 cd/A and 0.53 %, respectively.