Luminescence due to intra- and inter-molecular transition in C70 single crystals

We have investigated absorption and luminescence spectra and temporal behaviors of luminescence in solutions and solids of C70. The luminescence bands observed for C70 in solution originate from the S1–S0 transition. The luminescence decay kinetics of C70 single crystal exhibits two-component decay with decay times of ∼400 ps and ∼1.4 ns. The fast component is assigned to the intra-molecular S1–S0 transition, and the slow one is attributable to the self-trapped state of charge-transfer exciton. It is found that there are two relaxation channels of photoexcitations in C70 crystals: intra-molecular and inter-molecular relaxations.