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 ⊿E_ST (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.