Efficient Multiexciton Energy Transfer from Quantum Dots to Molecular Triplets

Area of Science:

• Materials Science
• Photochemistry
• Quantum Chemistry

Background:

• Colloidal quantum dots (QDs) are vital for light harvesting but suffer from rapid multiexciton decay via Auger recombination.
• Existing methods for multiexciton utilization are limited by charge recombination.
• Triplet energy transfer from QDs to molecules offers long-term exciton energy storage, but multiexciton transfer was previously unachieved.

Purpose of the Study:

• To demonstrate efficient multiexciton energy transfer from quantum dots (QDs) to surface-anchored aggregation-induced-emission (AIE) molecules.
• To investigate the mechanism of stepwise charge-transfer for populating molecular triplet states.
• To explore the utilization of these multiexciton-derived triplet states for photochemical applications.

Main Methods:

• Utilized Cd, Pb-free ZnSe-based QDs functionalized with AIE molecules.
• Employed stepwise interfacial electron and hole transfer to dissociate multiexcitons and populate AIE triplet states.
• Quantified multiexciton dissociation efficiency and triplet energy transfer yields.

Main Results:

• Achieved highly efficient (96%) multiexciton dissociation even at high exciton numbers (⟨N⟩=5.2).
• Demonstrated efficient energy transfer from QD multiexcitons to AIE molecular triplets.
• Observed a near-linear increase in AIE triplet and singlet-oxygen yields with increasing exciton number (⟨N⟩).

Conclusions:

• Established efficient multiexciton energy transfer from QDs to AIE molecules via stepwise charge-transfer.
• Confirmed that multiexciton triplet energy transfer is as efficient as single-exciton transfer.
• Opened new avenues for utilizing multiexcitons in photochemical applications like singlet-oxygen generation and organic photocatalysis.