Energy relaxation dynamics of photoexcited C-60 solid

Abstract

The time-resolved photoluminescence (PL) of C-60 solid film was measured at various detection wavelengths, excitation laser fluences, and temperatures. Two emission bands were identified which possess different decay profiles, and these profiles exhibited completely opposite temperature dependence. The bands were attributed to free exciton states and self-trapped exciton states, which decay through diffusive recombination and activated intersystem crossing, respectively. For the latter case, a distinct rise component in the PL time profile was observed at low temperature. This strongly suggests that there exists a nonnegligible barrier between the free exciton states and self-trapped exciton states.