Electroabsorption measurements of polysquaraine

We report an electroabsorption signal for the main IR-Vis absorption peak in thin films of polysquaraine. Spectra from 1.0 to 2.0 eV at a temperature of 10 K show a positive peak at 1.29 eV, followed by a negative peak at 1.35 eV with vibronic structure on the high energy wing. The results are discussed in terms of a Stark effect on molecular states. Using the results a Stark shift of about 1 meV is calculated, consistent with values for other π-conjugated polymer systems.