ИСТИНА

Organic semiconducting materials promise the new generation of electronics especially in the light-emitting and photovoltaic applications, such as displays, lighting, solar cells and photodetectors. Thorough understanding of charge transport depending on the material structure is one of the main milestones on the way to an efficient device. Highly ordered organic semiconducting single crystals can be considered as a test bench for studying structure – semiconducting properties correlation on the molecular scale. Raman spectroscopy is considered a powerful tool for studying conjugated organic materials at the molecular level. Importantly, Raman spectroscopy could be used to probe intermolecular interactions using low frequency (LF) Raman spectra . Here, we present our recent results on Raman spectroscopy of thiophene−phenelyne co-oligomers (TPCOs) single crystals. These molecules are promising candidates for organic light emitting transistors (OLETs) combining efficient luminescence and charge transport properties. We show that Raman microscopy is sensitive to the orientation of single crystal domains. For that, we analyze the frequency range of covalent C—C vibrations and found clear domain boundaries. We also show that LF Raman spectroscopy can be used as a sensitive tool to study molecular packing and intermolecular interactions in a highly ordered crystal. Fig.1 shows typical dependence of LF Raman spectra of TCPO single crystal on temperature that can be used to analyze the dependence of molecular order and vibrations on temperature. Fig. 1. (a) Raman spectra for different temperatures; (b) LF Raman peak position dependence on temperature; (c) TPCO chemical structure. By studying the temperature data for the LF Raman spectra, we were able to correlate the intermolecular vibrations with the crystal structure parameters. The correlation between intermolecular packing, vibrations and the semiconducting properties of the crystals studied are discussed.