Efficient blue-green and white organic light-emitting diodes with a small-molecule host and cationic iridium complexes as dopants

Abstract

Using cationic iridium complexes as dopants and a small molecule, 9,9-bis[4-(3,6-di-tert-butylcarbazol-9-yl)phenyl]fluorene, as the host, efficient organic light-emitting diodes (OLEDs) have been fabricated from a solution process. The blue-green OLEDs achieve a peak current efficiency of 19.8 cd A−1 and a maximum brightness of 17700 cd m−2. White OLEDs have been fabricated with a peak current efficiency of 16.8 cd A−1 and Commission Internationale de l’Eclairage coordinates around (0.37, 0.44). It is suggested that cationic iridium complexes, in addition to their use in light-emitting electrochemical cells, are promising phosphorescent dopants for solution-processed small-molecule OLEDs.