Color tunable organic light-emitting diodes using coumarin dopants

A series of 4-hydroxy coumarin derivatives, C-1, C-2 and C-3, were synthesized, and their photoluminescence and electroluminescent properties were investigated. The peak emission wavelengths of the dopants can be tuned between 574 and 618 nm, depending upon the electronic properties of the substituents. Multilayer electroluminescent devices were fabricated using C-1, C-2 and C-3 as the dopants. Among these devices, an external quantum efficiency of 3.2% and a maximum brightness of 1.6 × 10⁴ cd/m² were achieved.