Theoretical study on optoelectronic properties of fluorene derivatives with pyrene-functional groups: Effect of the heteroatoms and pyrene substituting position

The geometries and photoelectric properties of pyrene-functional fluorene derivatives are investigated by detailed quantum-chemical methods, including density functional theory (DFT), time-dependent density functional theory (TD-DFT) and polarizable continuum model (PCM). The effects of the following factors on the properties were systemically analyzed: (1) the substituting position of the pyrene groups on the central fluorene; (2) the substitution of the central C by the heteroatoms; (3) the introduction of phenyl at the central C position. The rigid pyrene groups play a dominant role in determining their frontier molecular orbitals and reducing the reorganization energies. In these studied molecules, due to its large EST (the splitting between the lowest singlet and triplet excitation energies) and excellent and balanceable charge transport properties, DPF-2 should be a promising emission layer material. The host-guest systems composed of these emitters and rubrene are suitable for emission layer materials of white organic light-emitting devices.