Spectral Properties Of Perylene Under High Pressure

The dye molecules perylene and its derivates have good electron acceptor capacity,high absorption coefficient,high electron mobility,high fluorescence quantum yield,outstanding photophysical and photochemical stability.Thus,perylene and its derivates are widely used in solar cells,dye lasers,organic light-emitting diodes,fluorescent sensors and other optoelectronic devices.The molecular loops of perylene contain overlapping p-orbitals,which can extend above and below the plane of the molecule to form π-bonds.Such structure can be pressure-responsive and thus affect the optoelectronic properties of molecules.In order to explore the pressure response of perylene molecules,Raman spectroscopy and ultra-fast spectroscopy are performed with pressure as variable parameter.The Raman scattering process and relaxation process of perylene under pressure are analyzed.The results show that,with pressure increasing,the peak of Raman shifts to high wave numbers and the intensity of Raman decreases gradually.While,the steady-state absorption spectra undergo peaks red shift,band broaden,and gradually covers the entire visible band.When the pressure reaches 4.25 GPa,color of sample changes from the yellow to red,which indicates that pressure-induced discoloration of the perylene molecules.Furthermore,the perylene molecules can restore the original color with the pressure restoring.Under ambient conditions,the fast components of relaxation time decreases with wavelength increasing,which indicates that the low-lying excited states are all long-lived states.Under high pressure conditions,the interaction between perpendicular long axis dipoles between adjacent molecules increases and the probability of charge-transfer increases with pressure increasing.The main research content of this article:Part I,introduction.Firstly,high-pressure technology and the principle of diamond anvil cell(DAC)technology are introduced generally.The development and principle of ultra-fast technology are outlined.Secondly,the research background of this thesis is described in detail.Part II,experimental methods.Firstly,the assembling and sample loading of DAC is introduced.Secondly,the principle,instrument and manipulation of Raman spectroscopy is introduced.Secondly,home-built high-pressure femtosecond pump-probe set-up is introduced,in which the adjustment of optical path and the spectrum acquisition process are described in detail.Part III,data analysis.The spectra obtained in the experiment are summarized and analyzed.Raman spectroscopy,steady-state absorption spectroscopy,and time-resolved spectroscopy of perylene are systematically described under pressure.