Uncovering the Role of Hole Traps in Promoting Hole Transfer from Multiexcitonic Quantum Dots to Molecular Acceptors
| Autor: | Zi-jie Liu, Eran Rabani, Dipti Jasrasaria, Yi Liu, John P. Philbin, Matthew A. Kolaczkowski, Adam M. Schwartzberg, Daniel Weinberg, Arunima D. Balan, A. Paul Alivisatos, Chang Yan |
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| Rok vydání: | 2020 |
| Předmět: |
Physics
Auger effect General Engineering General Physics and Astronomy 02 engineering and technology Condensed Matter::Mesoscopic Systems and Quantum Hall Effect 010402 general chemistry 021001 nanoscience & nanotechnology 01 natural sciences 0104 chemical sciences symbols.namesake Quantum dot Chemical physics symbols Astrophysics::Solar and Stellar Astrophysics General Materials Science Astrophysics::Earth and Planetary Astrophysics 0210 nano-technology |
| Zdroj: | ACS Nano. 15:2281-2291 |
| ISSN: | 1936-086X 1936-0851 |
| DOI: | 10.1021/acsnano.0c08158 |
| Popis: | Understanding electronic dynamics in multiexcitonic quantum dots (QDs) is important for designing efficient systems useful in high power scenarios, such as solar concentrators and multielectron charge transfer. The multiple charge carriers within a QD can undergo undesired Auger recombination events, which rapidly annihilate carriers on picosecond time scales and generate heat from absorbed photons instead of useful work. Compared to the transfer of multiple electrons, the transfer of multiple holes has proven to be more difficult due to slower hole transfer rates. To probe the competition between Auger recombination and hole transfer in CdSe, CdS, and CdSe/CdS QDs of varying sizes, we synthesized a phenothiazine derivative with optimized functionalities for binding to QDs as a hole accepting ligand and for spectroscopic observation of hole transfer. Transient absorption spectroscopy was used to monitor the photoinduced absorption features from both trapped holes and oxidized ligands under excitation fluences where the averaged initial number of excitons in a QD ranged from ∼1 to 19. We observed fluence-dependent hole transfer kinetics that last around 100 ps longer than the predicted Auger recombination lifetimes, and the transfer of up to 3 holes per QD. Theoretical modeling of the kinetics suggests that binding of hole acceptors introduces trapping states significantly different from those in native QDs passivated with oleate ligands. Holes in these modified trap states have prolonged lifetimes, which promotes the hole transfer efficiency. These results highlight the beneficial role of hole-trapping states in devising hole transfer pathways in QD-based systems under multiexcitonic conditions. |
| Databáze: | OpenAIRE |
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