Comparison of Carrier Multiplication Yields in PbS and PbSe Nanocrystals: The Role of Competing Energy-Loss Processes

Stewart, J. T.; Padilha, Lázaro A.; Qazilbash, Muhammad; Pietryga, Jeffrey M.; Midgett, Aaron G.; Luther, Joseph M.; Beard, Matthew C.; Nozik, Arthur J.; Klimov, Victor I.

doi:10.1021/nl203367m

Cited by 114 publications

(187 citation statements)

References 52 publications

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“…36 As illustrated in Figure 1a, we generated MEs using the latter method. Since the behavior of MEs generated by either method has been shown to be the same, 28 the results of this study are valid also for the MEs generated by CM.…”

Section: Resultsmentioning

confidence: 99%

Observation of Biexcitons in Nanocrystal Solids in the Presence of Photocharging

et al. 2013

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In nanocrystal quantum dots (NQDs), generating multiexcitons offers an enabling tool for enhancing NQD-based devices. However, the photocharging effect makes understanding multiexciton kinetics in NQD solids fundamentally challenging, which is critically important for solid-state devices. To date, this lack of understanding and the spectralÀtemporal aspects of the multiexciton recombination still remain unresolved in solid NQD ensembles, which is mainly due to the confusion with recombination of carriers in charged NQDs. In this work, we reveal the spectralÀtemporal behavior of biexcitons (BXs) in the presence of photocharging using near-unity quantum yield CdSe/CdS NQDs exhibiting substantial suppression of Auger recombination. Here, recombinations of biexcitons and single excitons (Xs) are successfully resolved in the presence of trions in the ensemble measurements of time-correlated single-photon counting at variable excitation intensities and varying emission wavelengths. The spectral behaviors of BXs and Xs are obtained for three NQD samples with different core sizes, revealing the strength tunability of the XÀX interaction energy in these NQDs. The extraction of spectrally resolved X, BX, and trion kinetics, which are otherwise spectrally unresolved, is enabled by our approach introducing integrated time-resolved fluorescence. The results are further experimentally verified by cross-checking excitation intensity and exposure time dependencies as well as the temporal evolutions of the photoluminescence spectra, all of which prove to be consistent. The BX and X energies are also confirmed by theoretical calculations. These findings fill an important gap in understanding the spectral dynamics of multiexcitons in such NQD solids under the influence of photocharging effects, paving the way to engineering of multiexciton kinetics in nanocrystal optoelectronics, including NQD-based lasing, photovoltaics, and photodetection.

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Section: Resultsmentioning

confidence: 99%

Observation of Biexcitons in Nanocrystal Solids in the Presence of Photocharging

et al. 2013

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“…via an Auger process). In lead chalcogenide QDs, the latter process proceeds on 20−200 ps time scales [51,124]. As mentioned previously, charge separation can be at least two orders of magnitude faster if an ionising interface is in close proximity to the generated exciton [110].…”

Section: The Choice Of Qd Materialsmentioning

confidence: 80%

“…In these reports, the authors also find a close correlation between MEG th E and the MEG efficiency (η MEG ). While there seems to be general consensus that relaxed crystal momentum conservation rules in quantum-confined materials [47] contribute to MEG th E being close to 2E g , there is disagreement in the literature on how other quantum material properties such as discrete energy levels around the QD band gap [47] enhanced coulomb interaction in nanostructures of lower symmetry than spherical QDs [48] or the increased surface-tovolume ratio [49] contribute to the crucial MEG parameters MEG th E and η MEG [50,51]. What seems clear, however, is that materials with weak charge-phonon coupling (e.g.…”

Section: Enhancing CM In Qdsmentioning

confidence: 99%

Multiple exciton generation in quantum dot-based solar cells

et al. 2017

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Multiple exciton generation (MEG) in quantumconfined semiconductors is the process by which multiple bound charge-carrier pairs are generated after absorption of a single high-energy photon. Such charge-carrier multiplication effects have been highlighted as particularly beneficial for solar cells where they have the potential to increase the photocurrent significantly. Indeed, recent research efforts have proved that more than one chargecarrier pair per incident solar photon can be extracted in photovoltaic devices incorporating quantum-confined semiconductors. While these proof-of-concept applications underline the potential of MEG in solar cells, the impact of the carrier multiplication effect on the device performance remains rather low. This review covers recent advancements in the understanding and application of MEG as a photocurrent-enhancing mechanism in quantum dot-based photovoltaics.

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“…A 2011 study made the comparison between PbSe and PbS to determine why QY for PbSe seemed much higher [45]. ese two QDs are studied particularly as PbS QDs are stable in air and have the same structure as PbSe QDs which, as already mentioned, are relatively unstable in air.…”

Section: Pbx Quantum Dotsmentioning

confidence: 99%

Multiple Exciton Generation in Nanostructures for Advanced Photovoltaic Cells

Siemons

Serafini

2018

Journal of Nanotechnology

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is paper reviews both experimental and theoretical work on nanostructures showing high quantum yields due to the phenomenon of multiple exciton generation. It outlines the aims and barriers to progress in identifying further such nanostructures and also includes important developments concerning solar devices where nanostructures act as the light-absorbing component. It reports on both semiconductor and carbon structures, both monocomposite (of various dimensionalities) and heterogeneous. Finally, it looks at future directions that can be taken to push solar cell efficiency above the classic limit set by Shockley and Queisser in 1961.

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Comparison of Carrier Multiplication Yields in PbS and PbSe Nanocrystals: The Role of Competing Energy-Loss Processes

Cited by 114 publications

References 52 publications

Observation of Biexcitons in Nanocrystal Solids in the Presence of Photocharging

Observation of Biexcitons in Nanocrystal Solids in the Presence of Photocharging

Multiple exciton generation in quantum dot-based solar cells

Multiple Exciton Generation in Nanostructures for Advanced Photovoltaic Cells

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