The time dependence of the carrier relaxation in undoped solid C60 thin films has been studied by monitoring changes in the optical transmission upon photoexcitation at the HOMO- LUMO band edge. The relaxation closely follows a Kohlrausch-Williams-Watts decay with an exponent of (beta) equals 0.4. This functional form is typical of carrier relaxation associated with states of localized rather than extended character. Observation of this decay is highly dependent on film purity, which in turn is highly dependent on the methods used in the fullerene purification and separation processes. The effects of fullerene processing procedures on the observed carrier dynamics in solid C60 is discussed.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.