High Upconversion Efficiency from Hetero Triplet–Triplet Annihilation in Multiacceptor Systems

We report the observation of very high triplet–triplet annihilation (TTA) upconversion efficiency in single-sensitizer/multiacceptor systems. A hetero-TTA process between triplet acceptors of different types is believed to account for the synergistic effect leading to the high upconversion efficiency. The upconversion quantum yield of the dual-acceptor system is much higher than the sum of the two single-acceptor systems.