Photo- and electro-luminescence properties of the organic bipolar molecules containing phenothiazine and phenanthoimidazole moieties

Three new organic bipolar molecules containing phenothiazine and phenanthoimidazole moieties, 10-butyl-3-(phenanthroimidazol-2-yephenothiazine (PI-PTZ), 10-butyl-3((4-(tert-butyl)phenyephenanthroimidazol-2-yl) phenothiazine (PPI-PTZ) and 10-butyl-3,7-bis((4-(tert-butyl)phenyephenanthroimidazol-2-yephenothiazine (PPI-PTZ-PPI), were successfully synthesized for organic light-emitting devices. Their thermal stabilities, photophysical and electrochemical properties were investigated systematically. These compounds exhibited strong blue or blue-green emissions with photoluminescence quantum efficiency (Phi(f)) of 41.48 %, 40.51 % and 61.52 % in chloroform solutions, while their Phi(f) in the solid thin films decreased to 37.53 %, 34.05 % and 47.77 %, respectively. Furthermore, the vacuum-processed doped devices based on these compounds were fabricated, in which the devices based on the compound PPI-PTZ-PPI exhibited the best electroluminescence performance with a maximum brightness of 30,180 cd/m(2), a maximum current efficiency of 10.65 cd/A and a maximum external quantum efficiency (EQE) of 4.0 %.