Multiple Exciton Generation in PbSe Quantum Dots and Quantum Dot Solar Cells
Multiple exciton generation in quantum dots (QDs) has been intensively studied as a way to enhance solar energy conversion by channeling the excess photon energy (energy greater than the bandgap) to produce multiple electron-hole pairs. Among other useful properties, quantum confinement can both increase Coulomb interactions that drive the MEG process and decrease the electron-phonon coupling that cools hot-excitons in bulk semiconductors. We have demonstrated that MEG in PbSe QDs is about two times as efficient at producing multiple electron-hole pairs than bulk PbSe. I will discuss our recent results investigating MEG in PbSe, PbS and PbSxSe1-x, which exhibits an interesting size-dependence of the MEG efficiency. Thin films of electronically coupled PbSe QDs have shown promise in simple photon-to-electron conversion architectures with power conversion efficiencies above 5%. We recently reported an enhancement in the photocurrent resulting from MEG in PbSe QD-based solar cells. We find that the external quantum efficiency (spectrally resolved ratio of collected charge carriers to incident photons) peaked at 114% in the best devices measured, with an internal quantum efficiency of 130%. These results demonstrate that MEG charge carriers can be collected in suitably designed QD solar cells. We compare our results to transient absorption measurements and find reasonable agreement.
- Research Organization:
- National Renewable Energy Lab. (NREL), Golden, CO (United States)
- Sponsoring Organization:
- USDOE Office of Science, Basic Energy Sciences
- DOE Contract Number:
- AC36-08GO28308
- OSTI ID:
- 1087210
- Resource Relation:
- Conference: American Chemical Society. Abstracts of Papers of the 244th ACS National Meeting, 19-23 August 2012, Philadelphia, Pennsylvania; Related Information: Abstract No. ENFL-1
- Country of Publication:
- United States
- Language:
- English
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