Long-Lived Delayed Emission from CsPbBr₃ Perovskite Nanocrystals for Enhanced Photochemical Reactivity

Lead halide perovskite nanocrystals (NCs) developed in recent years are strong light absorbers and fast-yet-efficient emitters with many potential optoelectronic or quantum-optical applications. In terms of photochemistry, however, while strong light absorption is a desired property for a photosensitizer, the short exciton lifetime of these NCs (on the order of a few nanoseconds) strongly limits the efficiency of charge/energy extraction from these NCs and hence their photochemical reactivity. Herein, we report that in quantum-confined CsPbBr3 NCs surface-functionalized with phenanthrene ligands, triplet energy transfer from photoexcited NCs to phenanthrene is followed by thermally activated repopulation of NC excitons, leading to delayed NC emission as long as ∼80 μs at room temperature, four orders of magnitude longer than that of unmodified CsPbBr3 NCs (∼5 ns). Leveraging the exceptionally long lifetime, phenanthrene-functionalized CsPbBr3 NCs efficiently drive steady-state photoreduction reactions via diffusion-controlled electron transfer. This study establishes a general strategy for applying strongly light-absorbing NC materials to photochemical transformations.