Phosphorescent mechanism for single-dopant white OLED of FPt: electronic structure and electron exchange-induced energy transfer

A comprehensive theoretical model of electron exchange-induced energy transfer combined with the CASPT2//CASSCF theory is first applied to explore the mechanism of tunable emission for the single-dopant WOLED of FPt and the related photophysical processes. The monomer-like bluish emission is demonstrated to depend on the efficiency of direction-specific charge transfer along O1 → Pt → pyridinyl ring, while the dimer-like reddish emission from the TLC state is dominated by the electron exchange that takes place between the TMLCTx and TLC states via the ground state. The strategy of molecular design is proposed to improve the efficiency of emission for the analogous C⁁NPt(O⁁O) complex on the basis of accurate electronic structure calculations and quantitative rates of Dexter energy transfer as well as comparisons with the case of Pt-4.