The 4th International Conference on Matter and Radiation at Extremes (ICMRE 2019)

533 / 2019-03-19 22:44:43

Tunable Photoluminescence of Organic Molecular Crystals under High Pressure

Photoluminescence,Diphenylfluorenone,High pressure

Plenary track > High Pressure Physics and Materials Science

Pressure is a powerful tool to modulate the crystal structure and the molecular packing, especially for supramolecular systems. In situ high-pressure IR spectra and synchrotron X-ray diffraction (XRD) have been employed to investigate the behavior of the organic solid-state light-emitting supramolecular material diphenylfluorenone (DPFO) crystals under high pressure. The reversible phase transition at around 3 GPa have been corroborated by experimental results. Further analysis of in situ photoluminescence spectra indicate the fluorescence shifts continuously to longer wavelength with obvious decrease of its intensity when we applied pressure to DPFO. Remarkably, a red-shift of about 300 nm was observed for its PL peak when applying the pressure to 13.32 GPa. Applying pressure to DPFO crystals also leads to the remarkable color variation from yellow to red after phase transition. In situ UV-vis absorption spectra show red-shift of a new absorption peak across nearly entire visible light region corresponding to the color variation. Theoretical calculations show the intermolecular - interactions and the overlap of the molecular oribitals in the new phase are responsible for the red shift in the PL and UV-vis absorption spectra. DPFO can be used as pressure-responsive optical molecular switch which can both control shift and intensity of fluorescence. Furthermore, this work reveals the application of high pressure technique is a straightforward and effective way to explore the structural and optical properties of organic materials.