8:30 AM - 8:45 AM
▲ [9a-Z04-1] Strain-Enhanced Luminescence in Octabutoxy Phthalocyanine Small Molecule Thin Films
Keywords:thin film, Phthalocyanine, Strain-Enhanced
Phthalocyanines (Pc’s) exhibit high mobilities and long-range interactions due to the highly directional π-orbital overlap and are alternative for certain traditional silicon-based semiconductor applications. Long range ordered thin films with macroscopic grain sizes containing octabutoxy phthalocyanine small molecules were prepared with solution-based process pen writing technique. The typical grain sizes are orders of magnitude larger that the diffraction-limited focused white light beam diameters. Disordered thin film was also prepared with spin coating technique. Crystals are randomly oriented in such thin films and are only bound by week interaction. Absorption spectra indicates additional exciton states (between 750 nm and 890 nm) in the bandgap arise due to the long-range interactions between molecules along the stacking axis. Incident light K-vector resolved absorption/linear dichroism experiment result further indicates that this exciton state is perpendicular to the molecule stacking axis within plane. The effect of stress on the exciton states was investigated by applying uniaxial strain along molecule stacking axis of ordered thin films on flexible substrate. Band gap absorption undergoes a red shift from 861 nm to 868 nm under 28.0% applied strain with no significant difference in absorbance. However, photoluminescence (PL) results show that the emission peak position from the ordered thin film undergoes a much larger red shift around 30 nm (from 890 nm to 919 nm) and the emission intensity greatly increases by 78.8%, as the applied strain increases from 0 to 18%. Further experiment involving low temperature PL and tip-enhanced Raman spectra under applied strain would be conducted to gain more insight of the effect of stress on the intermolecular interaction and optical property of the OBPc 2D thin film.