Nongeminate Radiative Recombination of Free Charges in Cation-Exchanged PbS Quantum Dot Films
Using photoluminescence (PL) spectroscopy we explore the radiative recombination pathways in PbS quantum dots (QDs) synthesized by two methods. We compare conventionally synthesized PbS from a PbO precursor to PbS synthesized using cation-exchange from CdS QDs. We show that strongly coupled films of PbS QDs from the cation-exchange luminesce with significant efficiency at room temperature. This is in stark contrast to conventional PbS QDs, which have exceedingly weak room temperature emission. Moreover, the power dependence of the emission is quadratic, indicating bimolecular radiative recombination that is reasonably competitive with trap-assisted recombination, a feature previously unreported in coupled PbS QD films. We interpret these results in terms of a greatly reduced defect concentration for cation-exchanged QDs that mitigates the influence of trap-assisted recombination. Cation-exchanged QDs have recently been employed in highly efficient and air-stable lead chalcogenide QD devices, and the reduced number of trap states inferred here may lead to improved current collection and higher open circuit voltage.
- Research Organization:
- Energy Frontier Research Centers (EFRC) (United States). Center for Advanced Solar Photophysics (CASP); National Renewable Energy Laboratory (NREL), Golden, CO (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- AC36-08GO28308
- OSTI ID:
- 1257548
- Report Number(s):
- NREL/JA-5900-64153
- Journal Information:
- Chemical Physics, Vol. 471; Related Information: Chemical Physics; ISSN 0301-0104
- Publisher:
- Elsevier
- Country of Publication:
- United States
- Language:
- English
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journal | January 2017 |
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journal | October 2018 |
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