We compared detailed dynamics of the excited-state absorption for C60 in solution, thin films, and entrapped in an inorganic sol-gel glass matrix. Our results demonstrate that the microscopic morphology of the C60 molecules plays a crucial role in determining the relaxation dynamics. This is a key factor for applications in optical limiting for nanosecond pulses using reverse saturable absorption. We find that the dynamics of our C60-glass composites occur on long (ns) timescales, comparable to those in solution; thin film samples, by contrast, show rapid decay (60-sol-gel glass composites contain C60 in a molecular dispersion, and are suitable candidates for solid-state optical limiting. Multispectral analysis of the decay dynamics in solution allows accurate determination of both the intersystem crossing time (600±100ps) and the relative strengths of the singlet and triplet excited-state cross sections as a function of wavelength from 450-950 nm. The triplet excited-state cross section is greater than that for the singlet excited-state over the range from 620-810 nm.
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