We present a novel method to detect and characterize the properties of defect-induced excitons in molecular crystals. By driving ultrafast coherent evolution along different normal coordinates using an impulsive Raman pump pulse, we construct vibrational coherence spectra detailing the presence of discrete electronic states inside the bandgap of diphenyl tetracene. The mode dependence of these coherence spectra indicate defects cause efficient sub-gap luminescence while their polarization dependence suggests assignment of specific structrual defects. We further propose this technique as a tool to understand defect-structure relationships in both traditional and emergent semiconducting materials.

Characterizing defect-induced excitons with coherent vibrational spectroscopy

256th National Meeting (2018)

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