Investigating Energy-Transfer Interactions in Perovskite Quantum Dot–Dye Assemblies

Colloidal quantum dots (QDs) exhibit several advantageous photophysical properties combined with a high surface-to-volume ratio, making them very attractive for use in processes relying on energy-transfer (ET) interactions. We have tested the effectiveness of CsPbBr3 perovskite quantum dots (PQDs) as energy-transfer donors in hybrid PQD–dye assemblies. We combined PQDs and various cyanine dye molecules that present zwitterionic moieties and/or salt groups to promote tailored binding via electrostatic interactions and control the spectral overlap in PQD–dye pairs. This enabled the manipulation of the donor–acceptor stoichiometry of the assemblies. Using steady-state and time-resolved fluorescence spectroscopy, we evaluated the impact of varying the dye structure, photophysical characteristics, and dye-to-PQD ratio on the fluorescence properties of these hybrid conjugates. We find that the fluorescence quenching efficiency measured for these assemblies depends on key parameters, such as spectral overlap and number of dyes per assembly (or valence). Thorough analysis of our results indicates that invoking the Förster dipole–dipole and Dexter charge-transfer interaction mechanisms provides the best interpretation of the energy-transfer interaction in these donor–acceptor assemblies.