New Light Emitting Materials: Alternating Copolymers with Hole Transport and Emitting Chrompophores

摘要

A new type of novel high-efficiency light-emitting nitrogen-containing poly-(phenylene vinylene) (PPV)-related copolymers,which have hole-transfer moieties such as triphenylamine (TPA) and conjugated aromatic units such as 4,4'-biphenylene,1,4-phenylene,2,5-dimethyl-1,4-phenylene,1,4- or 1,5-naphthylene,and 9,10-an-thrylene,was designed and synthesized by the well-known Wittting-Hornor reaction.The resulting alternating copolymers were highly soluble in common organic solvents.They can spin-cast onto various substrates to give highly transparent homogeneous thin films without heat treatment.The introduction of TPA units in the PPV backbone improved processibility and limited the #pi#-conjugation length.Furthermore,the additional #pi#-electron delocalization between the lone-paired electron in the nitrogen atom and #pi#-electrons in the conjugated units contributed to the improvement of the fluores-cence quantum yields of these copolymers.All these alternating copolymers except TPA-PAV have high-effciency photoluminescence and they are very promising for light-emitting diodes (LEDs).It is very promising that TPA-PAV will emit white light when used in LED device due to the broad emission spectra.The origin of the broad spectrum is contributed by teh charge-transfer complex formation,which can be proved by the absorption and emission spectra of TPA-PAV solutions.When the aromatic units were 1,4-phenylene,1,4- or 1,5-naphthylene,4,4'-biphenylene,and 9,10-anthrylene,respectively,with increase of the capability to accept electrons in aromatic units,the charge transfer from TPA to aromatic units occurred;consequently,the fluorescence quantum yield decreased.The introduction of the alkoxy-substitute group on the aromatic units in the polymer backbone caused the red shift of the absorption and emission spectra of the copolymers due to the stronger delocalization of the #pi#-conjugated system.