一种基于芴的大环结构的有效降低内重组能的理论研究

Organic semiconductor materials are widely used in organic light-emitting diodes (OLEDs), organic field-effect transistors (OFETs), and organic solar cells (OSCs), but their low mobility is not conducive to electron transport. In this work, a novel class of grid structures based on fluorene (OF) with a “口” structure has been designed and calculated, which has a geometric structure that can extend laterally compared with ordinary macrocyclic molecules. Density functional theory was utilized to study its molecular structure, ring strain energy, and various electronic properties, including molecular orbitals, adiabatic ionization potential, adiabatic electron affinity potentials, and reorganization energies. In addition, the weak interactions within molecules and the contribution of each vibration mode to the reorganization energy of OF were investigated by using non-covalent interaction analysis and Normal Mode (NM) analysis, respectively. The results show that OF has a weak ring strain energy (8.20 kJ/mol) which will be easily synthesized. Through intramolecular weak interaction analysis, it is found that in cis-OF the two fluorene elements on the beam are close and produce a certain angle, the π-π interaction is generated. Compared with Bis-Fl1, Bis-Fl2, Quarter-Fl1 and Quarter-Fl2, the energy gap of OF molecules decreases, the highest occupied molecular orbital (HOMO) energy level increases, and the lowest unoccupied molecular orbital (LUMO) energy level decreases, corresponding to adiabatic ionization potential (IPa) and adiabatic electron affinity(EAa), that is, the IPa of OF molecules decreases and EAa increases, which proves that the lattice effect can improve the hole and electron injection ability of molecules. At the same time, OF has a lower IPa which would be a very potential p-type molecular material. Interestingly, the reorganization energy of both OF molecules decreased compared with BF and QF, indicating that the lattice effect is an effective way to reduce the hole and electron reorganization energy which provides a strategy for the design of organic semiconductor materials with excellent charge transport properties.