Red-light-emitting diodes via efficient energy transfer from poly(9,9-dioctylfluorene) to tetraphenylporphyrin

We present a system of a blue-light-emitting host polymer, poly(9,9-dioctylfluorene) [PFO], and a red-light-emitting molecular guest, tetraphenylporphyrin [TPP], suitable for use in light-emitting diodes (LEDs). The strong overlap of the Soret absorption band of TPP and the 0-0 emission peak of PFO results in very efficient Forster transfer. We calculate a Forster transfer radius of 5.4 nm and determine that at TPP concentrations greater than 0.4%, at least 95% of the singlet excitons photogenerated on the PFO is transferred to the TPP. TPP-doped PFO LEDs have a maximum external electroluminescence quantum yield of 0.9% at a luminance of 90 cd/m(2) in the red. (C) 2000 Elsevier Science S.A. All rights reserved.