Photophysics and thermally activated delayed fluorescence (TADF) of fullerene C70 and C70 methano and pseudodihydro monoadducts: A comparative study

A comparative study of the photophysical properties of pristine C 70 and two C 70 derivatives, including their thermally activated delayed fluorescence (TADF) is reported. It is observed that the addition of a substituent group to the C 70 cage -like structure changes both the radiative and the nonradiative rate constants, the change being more pronounced for the nonradiative processes (S 1 -> S 0 internal conversion and S 1 -> T 1 and T 1 -> S 0 intersystem crossings). A new method of TADF analysis (global analysis of time -resolved and steady-state data) is presented and applied. Both derivatives are found to display a less efficient TADF when compared with C 70 .