A Surface Engineering Approach for Promoting Dexter Energy Transfer from Lead Halide Perovskite Nanocrystals

Efficient Dexter energy transfer from colloidal semiconductor nanocrystals lays the foundation for applications like photocatalysis and photon upconversion. We design a two-step functionalization strategy based on aromatic zwitterionic anchoring motifs to fix molecular triplet acceptors to the surface of CsPbBr3 perovskite nanocrystal (PNC), which increases the energy transfer rate by 120-fold. The binding condition of triplet acceptors and the influence on energy transfer during each surface treatment step are illustrated using steady-state and time-resolved optical spectroscopies and NMR. The results show that this new strategy can preclude competitive adsorption from residual synthetic ligands and achieve stable anchoring for triplet acceptors. Compared to acceptors that undergo rapid exchange on and off the dynamic PNC surface, the fixation significantly strengthens the electronic coupling with the PNC and hence promotes the Dexter energy transfer. Our strategy can be extended for quantitatively grafting other functional groups that require strong electronic coupling with lead halide perovskite surface.