High efficiency deep-blue organic light-emitting diode with a blue dye in low-polarity host

A high efficiency deep-blue organic light-emitting diode was fabricated using a blue light-emitting dye, 2,7-bis{2[phenyl(m-tolyl)amino]-9,9-dimethyl-fluorene-7-yl}-9,9-dimethyl—fluorene, doped in a low-polarity host, 4,4′-bis(9-carbazolyl)-biphenyl. The resulting device showed a highly saturated blue light with Commission Internationale de l’Eclairage coordinates of (0.14, 0.08) and a record-high external quantum efficiency of 5.1% at 100cd∕m2. The highly saturated blue emission may be attributed to effective solid-state solvation of the employed host, being able to effectively separate the blue dopants due to similar host-guest polarity. The high efficiency may result from efficient energy transfer from the host to dopant and a proper device architecture, leading excitons to favorably form on the host instead of on the dopant.