ENERGY RELAXATION DYNAMICS OF PHOTOEXCITED C-60 SOLID

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