Non-coherent photon upconversion by rapid intramolecular triplet-triplet annihilation has been observed following nanosecond laser excitation of Ru(dmb)(3) and sequential two-fold triplet energy sensitization of a polymer containing 30 pendant diphenylanthracene groups. A global kinetic analysis of the system has been performed; the intramolecular annihilation step occurs on a sub-nanosecond time scale. (C) 2014 Elsevier B.V. All rights reserved.