Light-emitting substituted polyacetylenes

A series of polyacetylene derivatives such as polyl(o-i-propylphenyl)acetyl ene] (PPA-iPr), poly[1-(p-n-butylphenyl)-2-phenylacetylene] (PDPA-nBu), and poly(1-hexyl-2-n-phenylacetylene) (PHPA) are systematically studied and co mpared, with emphasis on the dependence of the luminescence efficiency on t he side groups and the optical and electronic excitation processes in the p olymers. Orange-red (600 nm), green (530 nm), and blue (450 nm) photolumine scent (PL) and electroluminescent (EL) emissions from these polymers are ob served. The corresponding PL quantum efficiencies are measured using an int egrating sphere and found to be lower than 0.1% for PPA-iPr, 49% for PDPA-n Bu, 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 photoele ctron spectroscopy (UPS). It is shown that some of the substituted polyacet ylenes can be employed for lightemittingdiode (LED) fabrication, the quantu m efficiencies of which are comparable to those of other light-emitting pol ymers.