Abstract
New conjugated polymers based on separated PPV-type chromophores and incorporating different types of solubilizing side-groups (ethoxy:
P1, hexyloxy:
P2, dodecyloxy:
P3 and benzyloxy:
P4) were synthesized via Wittig polycondensation, using a series of bisphenol A-derived di(triphenylphosphonium) salts as starting monomers. The polymers are soluble in common organic solvents and their structures were confirmed by
1H NMR,
13C NMR and FTIR spectroscopies. The optical properties of these materials were investigated by UV–vis absorption and fluorescence spectroscopies. In dilute solution, quasi-identical fluorescence spectra were obtained and all the polymers showed a blue emission (420, 445
nm) and a narrow spectrum. In thin solid films, the polymers show side-group-dependent optical behavior and, whereas the emission remains blue in the case of
P2,
P3 and
P4, a green fluorescence was observed for the ethoxylated polymer
P1. From cyclic voltammetry analysis, the electrochemical band gaps were estimated to be 2.99, 3.07, 3.15 and 3.06
eV for
P1,
P2,
P3 and
P4, respectively. Single-layer diode devices of the [indium tin oxide/polymer/aluminum] configuration have been fabricated and show relatively low turn-on voltages between 2.6 and 4.9
V.