The optical processes that occur in π conjugated materials will bedescribed in Chapter 8. By way of example, Fig. 1.6 shows the absorptionspectrum of the technologically important polyfluorene-based polymercalled ‘F8’. Thin film samples of this material are typically preparedby spin coating the molecules onto a glass slide. The data in Fig. 1.6show that the polymer is transparent throughout most of the visiblespectral region, but absorbs strongly at ultraviolet wavelengths. Thebroad absorption band which peaks at 380nm is caused by vibrational–electronic transitions to the first singlet excited state of the molecule.This band extends slightly into the blue spectral region, and gives thematerial a pale yellow colour
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