ELECTROABSORPTION SPECTRUM OF TETRACENE - HIGH-FIELD MEASUREMENTS ON POLYCRYSTALLINE SAMPLES

Sandwich cell electro-absorption (EA) experiments on polycrystalline tetracene samples are reported. Numerical resolution of the high energy part of the measured EA spectrum into individual bands exhibits a large second derivative contribution from charge-transfer (CT) states, not expected for this geometry of the experiment and texture of the samples. Deviations of the crystallites from the orientation where the ab plane is parallel to the substrate are suggested as the main reason of this behaviour. The new bands observed at 3.26 and 3.38 eV may contain a substantial contribution from the CT states where the electron and the hole are in different ab planes of the crystal.