The photophysical and electrochemical properties of poly(PCT-T) and poly(PCT-2T) were investigated by UV/vis absorption and photoluminescence (PL) spectroscopy as well as cyclic voltammetry (CV) (Figure ) and compared to the properties of PCT. The key characteristics obtained from these measurements are summarized in Tables and. Solution UV/vis absorption measurements were performed in CHCl3 (solid lines in Figure ), showing one absorption band with a maximum at 305 nm for poly(PCT-T) and two absorption bands with maxima at 308 nm and 374 nm for poly(PCT-2T), with the (first) absorption maximum being almost identical to the absorption maximum of PCT at 306 nm. Similar observations were made in the thin film measurements (Figure ), with absorption maxima at 318 nm for PCT, 330 nm for poly(PCT-T), and 314 nm and 379 nm for poly(PCT-2T). However, significant peak broadening and a drastic redshift of the absorption onset was observed in the thin films. The rather large optical gaps (Eg,opt) in solution of 3.2 eV for poly(PCT-T) and 2.7 eV for poly(PCT-2T), determined from the absorption onsets, are drastically reduced in the solid state, with an absorption tail to approximately 700 nm (corresponding to 1.8 eV) found for poly(PCT-2T).