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The delayed luminescence and phosphorescence of ladder-type methyl-poly(para-phenylene) (MeLPPP) doped with benzil at a concentration of 20% by weight has been measured. The introduction of benzil leads to a dramatic reduction of the polymer singlet emission. At the same time, a new band with maximum at 611 nm appears, corresponding to the phosphorescence of MeLPPP. The phosphorescence decay on the short time scale is close to an exponential law with a time decay of 15 ms. This indicates that benzil can efficiently sensitize the phosphorescence of the polymer. In addition, a broad and featureless emission is observed in the delayed luminescence spectra of benzil-doped MeLPPP, which is attributed to an exciplex formed between the polymer host and the dopant. We further observe that the delayed fluorescence is enhanced by the addition of benzil. It is concluded that the delayed fluorescence of benzil-doped MeLPPP is mainly due to the annihilation of triplet excitons on the polymer. Finally, efficient triplet-triplet energy transfer from the benzil-doped polymer to the red-emitting phosphorescent dye Pt(II)octaethylporphyrin is established. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The question of the origin of delayed fluorescence from a phenyl-substituted poly(p-phenylenevinylene)-type copolymer (Ph-PPV) is addressed. Two origins have to be considered, i.e., triplet-triplet annihilation and recombination of geminate electron-hole pairs. Ph-PPV is investigated in the form of two different samples, namely diluted in 2-methyltetrahydrofuran (MTHF) glass at 80 K and as a thin film of optical density of 0.6. It will be shown that in the diluted solution, delayed fluorescence is due to triplet-triplet annihilation and in the thin film, it is due to geminate pair recombination. The assignment of delayed fluorescence to geminate pair recombination in the thin film could be made due to delayed fluorescence experiments under applying an electric field of 2 × 10[SUP6] V/cm. The delayed fluorescence is strongly influenced by the electric field which is a sign that charged species, i.e., geminate electron-hole pairs, are involved in the process of delayed fluorescence. [ABSTRACT FROM AUTHOR]

Abstract: The luminescence of a ladder-type methyl-poly(para-phenylene) (MeLPPP) doped with platinum–porphyrin dye PtOEP covering the concentration 10−3–5% by weight has been measured employing cw and transient techniques. Upon excitation into the range of absorption of the host, strong phosphorescence of the dopant is observed. Possible ways of populating the dopant triplet state are considered. [Copyright &y& Elsevier]

Luminescence of a ladder-type methyl-poly(para-phenylene) (MeLPPP) doped with 5% (by weight) platinum-porphyrin (PtOEP) has been investigated. It is shown that upon exciting in the spectral range of absorption of the guest the delayed fluorescence of the polymer is observed. Based upon field quenching of delayed fluorescence it is argued that it originates from an exciplex between PtOEP and MeLPPP generated by exciting the S1 state of PtOEP. [Copyright &y& Elsevier]

The luminescence of a ladder-type methyl-poly(para-phenylene) (MeLPPP) doped by platinum-porphyrin dye PtOEP covering the concentration 10−3 to 5% by weight has been measured employing cw and transient techniques. Upon excitating into the range of absorption of the host strong phosphorescence of the dopant is observed. Possible ways of populating of the dopant triplet state are considered. It is shown that the main channel is singlet–singlet energy transfer among chromophor groups of the polymer followed by Fo¨rster-type transfer to the guest and subsequent intersystem crossing. [Copyright &y& Elsevier]