Time-resolved study of luminescence in highly luminescent disubstituted polyacetylene and its blend with poorly luminescent monosubstituted polyacetylene

Abstract

A highly luminescent disubstituted polyacetylene, poly(1-phenyl-2-$p\ensuremath{-}n$-butylphenylacetylene) $(\mathrm{PDPA}\ensuremath{-}n\mathrm{Bu}),$ and its blend with a poorly luminescent monosubstituted polyacetylene, poly(1-$o$-trimethylsilylphenylacetylene) $(\mathrm{PPA}\ensuremath{-}o{\mathrm{SiMe}}_{3})$, are studied by time-resolved photoluminescence (PL) spectroscopy. In pure $\mathrm{PDPA}\ensuremath{-}n\mathrm{Bu},$ PL intensity at short wavelength decays faster than that at long wavelength, whereas PL spectra exhibit a dynamic Stokes shift to longer wavelengths with time. In blends of PDPA-$n\mathrm{B}\mathrm{u}/\mathrm{P}\mathrm{P}\mathrm{A}\ensuremath{-}o{\mathrm{SiMe}}_{3},$ only PL originating from $\mathrm{PDPA}\ensuremath{-}n\mathrm{Bu}$ is observed, without contribution from $\mathrm{PPA}\ensuremath{-}o{\mathrm{SiMe}}_{3}.$ The PL lifetime drastically decreases upon mixing a small amount of $\mathrm{PPA}\ensuremath{-}o{\mathrm{SiMe}}_{3}$ in $\mathrm{PDPA}\ensuremath{-}n\mathrm{Bu}.$ The PL characteristics of pure $\mathrm{PDPA}\ensuremath{-}n\mathrm{Bu}$ and its blend with $\mathrm{PPA}\ensuremath{-}o{\mathrm{SiMe}}_{3}$ are discussed in terms of lattice/vibrational relaxation of the excitonic state and exciton migration.