Triplet–Triplet Energy Transfer inside the Single Organic Nanocrystal Revealed by Microscopic Time Resolved Spectroscopy

The study on triplet–triplet energy transfer in organic photoelectric materials is desirable because triplet excitons are beneficial to storing and transporting excitation energy. Two platinum(II)-β-diketone complexes were selected as the energy transfer donor (PtD) and acceptor (PtA). We have studied the triplet–triplet energy transfer inside the single pure PtD and 2% PtA-doped nanocrystals by home-built microscopic time-resolved photoluminescence spectroscopy and transient absorption microscopy. The results indicate that the time constant of the triplet–triplet energy transfer between the donor and acceptor inside the 2% PtA-doped nanocrystal is ∼38 ns, the hopping process of the donor triplet inside the single nanocrystals has a diffusion constant of approximately 3 × 10–3 cm2 s–1, and the triplet transport distance along the long axis is approximately 70 nm in 7 ns. The long-range triplet transport between donors inside the nanocrystal would magnify the efficiency of light-harvesting energy transfer to the few doped acceptors.