Abstract
It is critical to find methods to control the thermodynamic driving force for photoexcited charge transfer from quantum dots (QDs) and explore how this affects charge transfer rates, since the efficiency of QD-based photovoltaic and photocatalysis technologies depends on both this rate and the associated energetic losses. In this work, we introduce a single-pot shell growth and Cu-catalyzed cation exchange method to synthesize CdxZn1-xSe/CdyZn1-yS QDs with tunable driving forces for electron transfer. Functionalizing them with two molecular electron acceptors-naphthalenediimide (NDI) and anthraquinone (AQ)-allowed us to probe nearly 1 eV of driving forces. For AQ, at lower driving forces, we find that higher Zn content results in a 130-fold increase of electron transfer rate constants. However, at higher driving forces electron transfer dynamics are unaltered. The data are understood using an Auger-assisted electron transfer model and analyzed with computational work to determine approximate binding geometries of these electron acceptors. Our work provides a method to tune QD reducing power and produces useful metrics for optimizing QD charge transfer systems that maximize rates of electron transfer while minimizing energetic losses.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 3209-3216 |
| Number of pages | 8 |
| Journal | Journal of Physical Chemistry Letters |
| Volume | 13 |
| Issue number | 14 |
| DOIs | |
| State | Published - Apr 14 2022 |
Funding
We are grateful for Maxwell Hoffman’s assistance with effective mass modeling, Sonja Lazovic’s insightful suggestions on figure aesthetics and accessibility, and Prof. David Hansen’s guidance with the microwave synthesis of NDI. We are thankful to the University of Massachusetts, Amherst, electron microscopy facilities for TEM imaging. Acknowledgment is made to the Donors of Petroleum Research Fund, administered by the American Chemical Society, for partial support of this research, under Grant Number 61874-UNI4. This material is based upon work supported by the National Science Foundation Graduate Research Fellowship Program under Grant No. DGE-1842165 (A.B.). Use of the Center for Nanoscale Materials, an Office of Science user facility, was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
ASJC Scopus subject areas
- General Materials Science
- Physical and Theoretical Chemistry
