In this thesis photoluminescence(PL) characteristics of conjugated polymers, poly(3,6-N-2-ethyhexyl carbazolyl cyano-terephthalidene) (Polymer 1), poly(3,6-N-2-ethyhexyl carbazolyl p-hexane-dioxy-cyano -4-biphenylidene)(Polymer 2), poly(2-ethynyl N-propargyl pyridinium bromide)(Polymer A), and poly(2-ethynyl N-propargyl pyridinium tosylate)(Polymer B) were studied. And the optical properties of poly (vinylcarbazole) were also investigated and compared with Polymer 1 and Polymer 2.
At room temperature, Polymer 1 and Polymer 2 show PL peaks near 2.36 eV and 2.54 eV, respectively. Due to the shortened conjugation length by the nonconjugated spacer group, the energy of PL of Polymer 2 is higher than that of Polymer 1. The shapes of PL spectra of both polymers are highly asymmetric with a long tail in the low energy region, which is considered due to the excimer emission. As the temperature increases, the PL intensity of Polymer 2 decreases and the peak shifts a little to higher energy. But the overall shape of the spectra does not change with the temperature variation. This difference from poly (vinylcarbazole) which has a new emission peak due to the high energy excimer with decreasing temperature shows that there is no emission due to another kind of excimer.
Polymer A and Polymer B show PL peaks near 2.36eV and 2.54eV, respectively. The PL peak of Polymer B shifts to higher energy due to the larger size of tosylate anion than that of bromine, which increases the steric hindrance between substituents, and so decreases the conjugation length. Temperature dependence of PL spectra in Polymer A and Polymer B is similar to that in Polymer 2.
