Optoelectrical Properties of a Novel Organic Semiconductor: 6,13- Dichloropentacene
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Organic semiconductors (OSCs), as a family of novel semiconducting materials, possess intriguing optoelectrical and mechanical properties enabling the applications to various new fields (such as flexible displays, solar cells and biosensors), which outreach the possibility of traditional semiconducting materials. Scientifically, new physical mechanisms are required to understand the light-matter interaction in OSCs and elucidate the related optical, electrical and optoelectrical properties. In this thesis, we adopt 6,13-dichloropentacene (DCP), as a platform to study light-matter interaction in OSCs. The ultimate goal is to better understand the physical mechanism related to the optoelectrical properties of organic semiconductors. Large-area well-aligned DCP nanobelt arrays have been obtained by solution methods. DCP molecules self-assemble into one-dimensional (1D) crystalline structures because of the strong anisotropic interactions between them. The highly ordered crystalline structure of DCP nanobelts enables precise polarization-resolved spectroscopic measurement. We show that both the intramolecular excitons and intermolecular excitons are formed in DCP nanobelts at optical excitation. The angular dependence of PL signals follows a quartic rule , which agrees well with the optical selection rule of individual DCP molecules in DCP nanobelts, and thus demonstrates that the PL emission arises only from the relaxation of intramolecular excitons despite the coexistence of intermolecular excitons. Moreover, the average PL polarization ratio reaches 0.91±0.02, which is among the highest range for organic semiconducting structures.