Red-light-driven photo(electro)catalysis in perovskite nanocrystal@donor-chromophore-acceptor hybrids through nonlinear exciton generation.

Harvesting low energy photons to drive chemical transformations remains a key challenge in light-to-chemical energy conversion. Herein, we report CsPbBr3 nanocrystals functionalized with a donor-chromophore-acceptor (DCA) Cu(I)-bisdiimine complex to enable charge transfer processes upon association with the nanocrystals. Under low power density (5 mW cm-2) red light photoexcitation (λmax = 625 nm), well below the bandgap energy, pristine CsPbBr3 nanocrystals exhibit band-edge photoluminescence with a nonlinear power dependence (n ≈ 1.6), demonstrating a nonlinear sub-bandgap response. Upon functionalization with the DCA, this emission is quenched while the structure of the nanocrystals is maintained, suggesting the introduction of additional nonradiative decay pathways. This interpretation was further supported by photoelectrochemistry, where DCA-functionalized nanocrystals adsorbed onto TiO2 yielded photoelectrodes that show measurable photocurrent (0.5 μA cm-2) under red light photoirradiation. Furthermore, this hybrid material was successfully used as a photocatalyst for styrene photopolymerization (29% isolated yield after 48 hours) under the same low power density red light. These findings open the door for the use of metal halide perovskite nanocrystals as low energy, red light photocatalysts.