Extremely low-threshold amplified spontaneous emission of 9,9′-spirobifluorene derivatives and electroluminescence from field-effect transistor structure

By doping 2,7-bis[4-(/V-carbazole)phenylvinyl]-9,9′-spirobifluorene (spiro-SBCz) into a wide energy gap 4,4′-bis(9-carbazole)-2,2′- biphenyl (CBP) host, we demonstrate an extremely low ASE threshold of E _th = (0.11±0.05) μJ cm^-2 (220 W cm^-2) which is the lowest ASE threshold ever reported. In addition, we confirmed that the spiro-SBCz thin film functions as an active light emitting layer in organic light-emitting diode (OLED) and a field-effect transistor (FET). In particular, we succeeded to obtain linear electroluminescence in the FET structure which will be useful for future organic laser diodes.