Optimization schemes for efficient multiple exciton generation and extraction in colloidal quantum dots

Damtie, Fikeraddis A.; Karki, Khadga Jung; Pullerits, Tõnu; Wacker, Andreas

doi:10.1063/1.4960507

Cited by 11 publications

(5 citation statements)

References 35 publications

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“…In traditional semiconductors, photogenerated energetic carriers, i.e., hot-carriers or hot-excitons, relax rapidly to band edges by the emission of phonons [ 8 , 9 ]. The multiexciton generation is a process in which two or even more electron–hole pairs are created in nanostructured semiconductors by absorbing a single high-energy photon [ 10 ]. It is difficult to harvest the excess energy above the band edges of the hot carriers due to the carrier relaxation that usually occurs on a sub-picosecond timescale [ 8 ].…”

Section: Introductionmentioning

confidence: 99%

Excitation Wavelength and Intensity-Dependent Multiexciton Dynamics in CsPbBr3 Nanocrystals

et al. 2021

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CsPbBr3 has attracted great attention due to unique optical properties. The understanding of the multiexciton process is crucial for improving the performance of the photoelectric devices based on CsPbBr3 nanocrystals. In this paper, the ultrafast dynamics of CsPbBr3 nanocrystals is investigated by using femtosecond transient absorption spectroscopy. It is found that Auger recombination lifetime increases with the decrease of the excitation intensity, while the trend is opposite for the hot-exciton cooling time. The time of the hot-carriers cooling to the band edge is increased when the excitation energy is increased from 2.82 eV (440 nm) to 3.82 eV (325 nm). The lifetime of the Auger recombination reaches the value of 126 ps with the excitation wavelength of 440 nm. The recombination lifetime of the single exciton is about 7 ns in CsPbBr3 nanocrystals determined by nanosecond time-resolved photoluminescence spectroscopy. The exciton binding energy is 44 meV for CsPbBr3 nanocrystals measured by the temperature-dependent steady-state photoluminescence spectroscopy. These findings provide a favorable insight into applications such as solar cells and light-emitting devices based on CsPbBr3 nanocrystals.

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Section: Introductionmentioning

confidence: 99%

Excitation Wavelength and Intensity-Dependent Multiexciton Dynamics in CsPbBr3 Nanocrystals

et al. 2021

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“…It would be interesting to study these processes experimentally by specifically designed optical pulses to provide specific single highly excited states similar to our states ñ A | and ñ B | in such nanowire structures. These experiments can be directly modeled by our approach, if the optical field is explicitly taken into account extending earlier work [50]. In this context it is also interesting to take into account non-ideal nanowire shapes seen in real systems, which, however, requires a substantially larger numerical effort.…”

Section: Resultsmentioning

confidence: 91%

“…Following the method used in [49,50] we model the time evolution of the density operator during the extraction of electrons using the Lindblad master equation…”

Section: Density Operator Master Equationmentioning

confidence: 99%

Electron extraction from excited quantum dots with higher order coulomb scattering

Kalaee

Wacker

2020

J. Phys. Commun.

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The electron kinetics in nanowire-based hot-carrier solar cells is studied, where both relaxation and extraction are considered concurrently. Our kinetics is formulated in the many-particle basis of the interacting system. Detailed comparison with simplified calculations based on product states shows that this includes the Coulomb interaction both in lowest and higher orders. While relaxation rates of 1 ps are obtained, if lowest order processes are available, timescales of tens of ps arise if these are not allowed for particular designs and initial conditions. Based on these calculations we quantify the second order effects and discuss the extraction efficiency, which remains low unless an energy filter by resonant tunnelling is applied.

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“…in an operational solar cell), strengthening the quantum confinement also weakens the interparticle coupling within the QD film [54] and is thus detrimental for efficient charge extraction. It follows that changing the quantum confinement has an effect not only on the MEG process itself, but also alters device parameters that are crucial for PV performance [29,49,[54][55][56].…”

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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Optimization schemes for efficient multiple exciton generation and extraction in colloidal quantum dots

Cited by 11 publications

References 35 publications

Excitation Wavelength and Intensity-Dependent Multiexciton Dynamics in CsPbBr3 Nanocrystals

Excitation Wavelength and Intensity-Dependent Multiexciton Dynamics in CsPbBr3 Nanocrystals

Electron extraction from excited quantum dots with higher order coulomb scattering

Multiple exciton generation in quantum dot-based solar cells

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