Influence of free carriers on exciton ground states in quantum wells

Klochikhin, A. A.; Кочерешко, В. П.; Tatarenko, S.

doi:10.1016/j.jlumin.2014.04.039

Cited by 5 publications

(5 citation statements)

References 19 publications

(45 reference statements)

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“…As has been previously reported, , the decay of this feature is fluence-dependent with a relatively long lifetime (> 1 ns). We note that the bleaching of exciton features is weakly visible in the NIR pumping data, consistent with the idea that exciton absorption will be a complex function of the local carrier concentration, available phase space, and local structural distortions. − …”

supporting

confidence: 83%

Edge States Drive Exciton Dissociation in Ruddlesden–Popper Lead Halide Perovskite Thin Films

Kinigstein

Tsai

Nie

et al. 2020

ACS Materials Lett.

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Efficient photovoltaic cells based on thin films of solution-processed 2D Ruddlesden–Popper hybrid perovskites (RPPs) represent an exciting breakthrough due to their enhanced tunability and chemical stability relative to those fabricated from 3D phases. However, reports of efficient charge separation and current collection are in apparent contradiction with the well-known enhancement of the exciton binding energy in multilayered halide perovskites, which should lower the device’s internal quantum efficiency and voltage. This controversy has led to various proposals for the electronic and physical structure of RPP thin films, including phase inhomogeneity as the driving force for exciton dissociation and transport. We address this apparent paradox in high-quality hot-cast RPP films by correlating ultrafast transient absorption spectroscopy with X-ray scattering measurements. We show that a hot-casting fabrication method produces highly phase pure n = 3 (BA)2(MA) n−1Pb n I3n+1 RPP structures. The high-phase purity and large grain sizes allow us to observe vertical transport of excitons via a diffusive process and allow us to determine that charge separation is primarily driven by dissociation at surface localized subgap electronic states. We analyze the differential absorption kinetics in films of varying thickness to directly determine that the excitonic diffusion constant is ∼0.18 cm2 s–1. We propose that a surface localized structural distortion, observed using surface selective grazing incidence X-ray scattering measurements, is responsible for the creation of the surface localized defect states. We find that the density and spatial distribution of these defect states is a function of preparation conditions.

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supporting

confidence: 83%

Edge States Drive Exciton Dissociation in Ruddlesden–Popper Lead Halide Perovskite Thin Films

Kinigstein

Tsai

Nie

et al. 2020

ACS Materials Lett.

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“…The electron-density dependened potential ( 5) is suitable for the description of the dependence of the exciton binding energy on the free career concentrations. Its advantages over the frequently used Yukawa potential are addressed in 29,30 For the trion case we simplify the problem and assume that the two electrons (we consider the X − case without loss of generality) are in the singlet state so that they are characterized by orthogonal spin functions and identical spatial wave functions. The trion binding energy may be found as the solution of the Coulomb problem with a hole of charge +e and mass m h and an electron pair of charge −2e and mass 2m e .…”

Section: /8mentioning

confidence: 99%

The interplay between excitons and trions in a monolayer of MoSe2

Lundt

Cherotchenko

Iff

et al. 2018

Applied Physics Letters

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We study the impact of a free carrier reservoir on the optical properties of excitonic and trionic complexes in a MoSe 2 monolayer at cryogenic temperatures. By applying photodoping via a non-resonant pump laser the electron density can be controlled in our sample and in turn the exciton and trion densities can be tuned. We find a significant increase of the trion binding energy in the presence of an induced electron gas both in power-and in time-resolved photoluminescence spectra. This behaviour is reproduced within the original variational approach that takes into account both screening and phase space filling effects.

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“…Optical spectra associated with excitons in the presence of a Fermi sea (FS) in bulk 1 or quantum well [2][3][4][5][6][7][8][9][10][11][12] semiconductors have been a subject of great interest for decades. Depending on the doping concentration, the Coulomb interaction between the photocreated exciton and the FS electrons can lead to various exotic complexes that come from the dressing of the exciton by Fermi-sea excitations, i.e., FS electron-hole pairs-the "FS hole" which corresponds to a missing electron in the doped conduction band, being fundamentally different from the valence hole making the exciton.…”

Section: Introductionmentioning

confidence: 99%

“…Depending on the doping concentration, the Coulomb interaction between the photocreated exciton and the FS electrons can lead to various exotic complexes that come from the dressing of the exciton by Fermi-sea excitations, i.e., FS electron-hole pairs-the "FS hole" which corresponds to a missing electron in the doped conduction band, being fundamentally different from the valence hole making the exciton. Interestingly, at low doping, a bound state can emerge from the interaction of a trion (two opposite-spin electrons bound to a valence hole) and a FS hole, known as Suris tetron [10][11][12] . When the FS contains just one electron, this 4-particle complex reduces to the conventional X − trion because there is no other hole state for the FS hole to scatter into to possibly form a bound state with the trion through repeated interactions.…”

Section: Introductionmentioning

confidence: 99%

“…This increase in energy difference contradicts common physical understanding: Indeed, the trion binding should decrease when the doping increases because of the increase of Pauli blocking and the reduction of Coulomb interaction due to screening by the doping electrons. Theoretical studies using many-body Green functions have con-firmed that absorption spectra should show two prominent peaks, separated by an energy difference that increases with doping [9][10][11][12] . Although the precise nature of these two peaks has not been established, it is clear that they must come from many-body interactions between an exciton and FS electron-hole pairs.…”

Section: Introductionmentioning

confidence: 99%

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Crossover from trion-hole complex to exciton-polaron inn-doped two-dimensional semiconductor quantum wells

2018

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We present a theoretical study of photo-absorption in n-doped two-dimensional (2D) and quasi-2D semiconductors that takes into account the interaction of the photocreated exciton with Fermi-sea (FS) electrons through (i) Pauli blocking, (ii) Coulomb screening, and (iii) excitation of FS electronhole pairs-that we here restrict to one. The system we tackle is thus made of one exciton plus zero or one FS electron-hole pair. At low doping, the system ground state is predominantly made of a "trion-hole"-a trion (two opposite-spin electrons plus a valence hole) weakly bound to a FS holewith a small exciton component. As the trion is poorly coupled to photon, the intensity of the lowest absorption peak is weak; it increases with doping, thanks to the growing exciton component, due to a larger coupling between 2-particle and 4-particle states. Under a further doping increase, the trion-hole complex is less bound because of Pauli blocking by FS electrons, and its energy increases. The lower peak then becomes predominantly due to an exciton dressed by FS electron-hole pairs, that is, an exciton-polaron. As a result, the absorption spectra of n-doped semiconductor quantum wells show two prominent peaks, the nature of the lowest peak turning from trion-hole to excitonpolaron under a doping increase. Our work also nails down the physical mechanism behind the increase with doping of the energy separation between the trion-hole peak and the exciton-polaron peak, even before the anti-crossing, as experimentally observed.

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Influence of free carriers on exciton ground states in quantum wells

Cited by 5 publications

References 19 publications

Edge States Drive Exciton Dissociation in Ruddlesden–Popper Lead Halide Perovskite Thin Films

Edge States Drive Exciton Dissociation in Ruddlesden–Popper Lead Halide Perovskite Thin Films

The interplay between excitons and trions in a monolayer of MoSe2

Crossover from trion-hole complex to exciton-polaron inn-doped two-dimensional semiconductor quantum wells

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