Vibronic coupling effect on intersystem crossing rates of TADF emitters

To take advantage of all the singlet and triplet excitons and then achieve 100%internal quantum efficiency in OLED devices,the scientists have proposed the thermally activated delayed fluorescence(TADF)strategy which tries to achieve"delayed"fluorescence by converting triplet excitons to singlet excitons through a reverse intersystem crossing(ISC/RISC)process with the help of thermal activation[1].In the early days,the efficient RISC processes were facilitated by a negligible energy gap(△E_(ST))and a large spin-orbit coupling(SOC)matrix element(SOCME)between the first singlet(S_(1))and triplet(T_(1))excited states.