Photodegradation-induced photoluminescence behaviors of π-conjugated polymers upon the doping of organometallic triplet emitters

The different effects on the photodegradation-induced photoluminescence (PL) of π-conjugated polymeric thin films upon the doping of Ir(III) containing triplet emitters in ambient conditions at room temperature were investigated. In this study, we prepared spin-coated thin films using three different polymer matrices including poly(9-vinylcarbazole) (PVK), poly[9,9-bis(2-ethylhexyl)fluorene-2,7-diyl] (PF2/6), and poly[2-(5′- cyano-5′-methyl-hexyloxy)-1,4-phenylene] (CNPPP) derivatives doped with (III) containing triplet emitters: Ir(III) bis[(4,6-fluorophenyl)-pyridinato-N, C²′] picolinate (FIrpic), or Ir(III)fac-tris(2-phenylpyridine) (Ir(ppy)₃), or Ir(III)bis(2-(2′-benzothienyl) pyridinato-N-acetylacetonate) (Ir(btp)₂acac). Using the doped films, and their neat films, on quartz substrates, the UV-Visible absorption (UV-Vis) and PL spectra were recorded under continuous illumination with the excitation wavelengths at the absorption maxima of the corresponding matrix polymers. The dopant effects on the photodegradation-induced PL were extracted from the kinetic data obtained from the doped films by subtracting the mutual degradation kinetics of their corresponding neat films. The obtained dopant effects show a strong correlation between the photo-induced PL degradation and the exciton migration behaviors.