The Fluorine And Cyano Substituent Effect On Supermolecular Structures And Their Photoelectronic Properties: A Theoretical Study

Organic functional materials are always processed in condensed state in devices. These condensed state are formed by molecules with supermolecular interactions which can dramatically effect on the photoelectronic properties and even determine the ability of devices. Hence, it is very significant to investigate and understand the mechanism of these interactions.In this dissertation, The fluorine(F) and cyano(CN) substituent effect on supermolecular structures and their photoelectronic properties have been systematically studied by theoretical method, which including five sections:1. The different substituent effects of F and CN in naphtho[2,3-b]thiophene(NaT) at the molecular and supramolecular levels on ambipolar charge transport have been investigated. All the analyses(such as reorganization energy, transfer integral, carrier mobility and so on) show that F and CN are playing a distinct role in NaT derivatives and CN is more suitable than F for ambipolar charge transport in NaT.2. The interactions between F or CN subsitituted corannulene(electron-withdrawing) and pyrene or coronene(electron-rich) have beed studied. The results show that CN can affect on the electronic structure more strongly than F, induce remarkable polarization and enhance the absorption at long wavelength.3. The interactions between pentagon–octagon–pentagon defect graphene(DG) and molecules with F and/or CN(FNa, TCNQ and F4TCNQ) were revealed. All the analyses indicate that the CN group in TCNQ and F4 TCNQ, rather than the F group in FNa, exhibit much stronger interactions via wavefunction overlap with DG, changing the bands near the Fermi level and enhancing the infrared light absorption significantly.4. The interactions between F or CN subsitituted(fluorene-thiophene)nanogrid(electron-rich) and C60(electron withdrawing) have beed investigated. The results show that both F and CN cannot change the energy level, but CN can decrease the Pauli repulsion between grid and C60, therefore induce the delocalization of LUMO and also CN can enhance the absorption at long wavelength. In addition CN can change the electron trap behaviour in condensed state.5. The F and CN subsitituted fluorene(electron-rich) and 4,5-diazafluorene(electron withdrawing) were noncovalently introduced in monolayer MoS2 by vertical way, and the noncovalent interactions have been investigated. The results show that all the molecules(except FDAF) cannot effect on the photoelectronic properties(except work function). CN subsitituted fluorene and 4,5-diazafluorene can dramatically change the work function about 1.1 eV.