Light-Emitting Substituted Polyacetylenes

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Abstract
A series of polyacetylene derivatives such as poly[(o-i-propylphenyl)acetylene] (PPA-iPr), poly[1-(p-n-butylphenyl)-2-phenylacetylene] (PDPA-nBu), and poly(1-hexyl-2-n-phenylacetylene) (PHPA) are systematically studied and compared, with emphasis on the dependence of the luminescence efficiency on the side groups and the optical and electronic excitation processes in the polymers. Orange-red (600 nm), green (530 nm), and blue (450 nm) photoluminescent (PL) and electroluminescent (EL) emissions from these polymers are observed. The corresponding PL quantum efficiencies are measured using an integrating sphere and found to be lower than 0.1% for PPA-iPr, 49% for PDPA-nBu, and 62% for PHPA. The ionization energies are 5.3, 5.2, and 5.9 eV for PPA-iPr, PDPA-nBu, and PHPA, respectively, measured by ultraviolet photoelectron spectroscopy (UPS). It is shown that some of the substituted polyacetylenes can be employed for lightemittingdiode (LED) fabrication, the quantum efficiencies of which are comparable to those of other light-emitting polymers.