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In this work we have revisited the charge-transfer crystal system perylene–TCNQ and found that this complex can crystallize with a 2:1 stoichiometric ratio in addition to the 1:1 and 3:1 stoichiometries previously observed. The vibrational and electronic properties of these perylene–TCNQ charge-transfer crystals have been investigated by means of Raman scattering measurements and density functional theory calculations. Electrical measurements were also performed by preparing organic field-effect transistors (OFETs) from the crystals. The Raman spectra in the low-frequency range (below 200 cm^–1) are found to be unique to the specific crystal structure and can therefore be used to determine the stoichiometry. The Raman data and the X-ray diffraction measurements indicate that at room temperature the amount of charge transferred to the TCNQ molecule is less than 0.2e for all three compounds, and is nearly …