Photophysics of Pt-porphyrin electrophosphorescent devices emitting in the near infrared

The triplet annihilation dynamics of near infrared organic light-emitting devices are studied with peak electrophosphorescence at a wavelength of 772 nm using a platinum-porphyrin derivative Pt(II)-tetraphenyltetrabenzoporphyrin as dopant. Both the photoluminescent decay transients of the thin films and the quantum efficiency versus current density characteristics of devices using tris(8-hydroxyquinoline) aluminum or 4 , 4 ′ -bis( N -carbazolyl)biphenyl (CBP) as hosts are fitted by a model based on triplet-triplet annihilation. When the phosphor is codoped with Ir(III) bis(2-phenyl quinolyl- N , C 2 ′ ) acetylacetonate in CBP, the quantum efficiency is enhanced, and the observed decrease of efficiency at high current densities is explained by field-induced charge pair dissociation. The external quantum efficiency has a maximum of ( 8.5 ± 0.3 ) % , decreasing to ( 5.0 ± 0.3 ) % at 1 mA ∕ cm 2 .