Room-Temperature Exciton Storage in Elongated Semiconductor Nanocrystals

Kraus, Robert; Lagoudakis, Pavlos G.; Rogach, Andrey L.; Talapin, Dmitri V.; Weller, Horst; Lupton, John M.; Feldmann, Jochen

doi:10.1103/physrevlett.98.017401

Cited by 112 publications

(105 citation statements)

References 30 publications

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“…The bulky arms effectively prevent aggregation between cores, which cannot be fully excluded in the CdSe/CdS sphere-rod structures studied previously. 23 With the tetrapods, one can therefore be certain that electric field effects arise purely from the intraparticle electronic structure, and not from bulk-like interactions between particles. Secondly, the absorption cross section of the CdS arms in the ultraviolet (UV) spectrum, where optical excitation occurs, is over 300 × larger than that of CdSe.…”

Section: Tetrapod Nanocrystals and Field-induced Luminescence Quementioning

confidence: 99%

“…Figure 1(b) displays the basic capacitive device geometry employed, as described previously, 23 consisting of two electrodes with insulating layers to prevent charge injection, and a spin-coated dispersion of the nanocrystals in polystyrene. We note that great care has to be taken when choosing deposition rates and the overall thickness to prevent the formation of pinholes, which can lead to current breakdown of the device.…”

Section: Tetrapod Nanocrystals and Field-induced Luminescence Quementioning

confidence: 99%

“…23 The storage mechanism can be described as a reversible transition between a direct radiative and an indirect nonradiative exciton state. [24][25][26][27][28] This nonradiative state is more reminiscent of spatially charge-separated excitations in coupled quantum well structures than of dipoleforbidden excitations such as the dark exciton in CdSe or triplet excitons in molecular semiconductors.…”

Section: Introductionmentioning

confidence: 99%

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Exciton storage in CdSe/CdS tetrapod semiconductor nanocrystals: Electric field effects on exciton and multiexciton states

et al. 2012

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CdSe/CdS nanocrystal tetrapods are interesting building blocks for excitonic circuits, where the flow of excitation energy is gated by an external stimulus. The physical morphology of the nanoparticle, along with the electronic structure, which favors electron delocalization between the two semiconductors, suggests that all orientations of a particle relative to an external electric field will allow for excitons to be dissociated, stored, and released at a later time. While this approach, in principle, works, and fluorescence quenching of over 95% can be achieved electrically, we find that discrete trap states within the CdS are required to dissociate and store the exciton. These states are rapidly filled up with increasing excitation density, leading to a dramatic reduction in quenching efficiency. Charge separation is not instantaneous on the CdS excitonic antennae in which light absorption occurs, but arises from the relaxed exciton following hole localization in the core. Consequently, whereas strong electromodulation of the core exciton is observed, the core multiexciton and the CdS arm exciton are not affected by an external electric field.

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Section: Tetrapod Nanocrystals and Field-induced Luminescence Quementioning

confidence: 99%

Section: Tetrapod Nanocrystals and Field-induced Luminescence Quementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Exciton storage in CdSe/CdS tetrapod semiconductor nanocrystals: Electric field effects on exciton and multiexciton states

et al. 2012

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“…In this way photodeposition can be used as a unique probe of both reduction and oxidation reaction pathways. This is one example of the new and exciting possibilities afforded by the combination of photodeposition and cutting edge colloidal synthesis [18][19][20] .…”

Section: Introductionmentioning

confidence: 99%

Photochemical Oxidative Growth of Iridium Oxide Nanoparticles on CdSe@CdS Nanorods

Kalisman

Nakibli

Amirav

2016

JoVE

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We demonstrate a procedure for the photochemical oxidative growth of iridium oxide catalysts on the surface of seeded cadmium selenidecadmium sulfide (CdSe@CdS) nanorod photocatalysts. Seeded rods are grown using a colloidal hot-injection method and then moved to an aqueous medium by ligand exchange. CdSe@CdS nanorods, an iridium precursor and other salts are mixed and illuminated. The deposition process is initiated by absorption of photons by the semiconductor particle, which results with formation of charge carriers that are used to promote redox reactions. To insure photochemical oxidative growth we used an electron scavenger. The photogenerated holes oxidize the iridium precursor, apparently in a mediated oxidative pathway. This results in the growth of high quality crystalline iridium oxide particles, ranging from 0.5 nm to about 3 nm, along the surface of the rod. Iridium oxide grown on CdSe@CdS heterostructures was studied by a variety of characterization methods, in order to evaluate its characteristics and quality. We explored means for control over particle size, crystallinity, deposition location on the CdS rod, and composition. Illumination time and excitation wavelength were found to be key parameters for such control. The influence of different growth conditions and the characterization of these heterostructures are described alongside a detailed description of their synthesis. Of significance is the fact that the addition of iridium oxide afforded the rods astounding photochemical stability under prolonged illumination in pure water (alleviating the requirement for hole scavengers). Video LinkThe video component of this article can be found at

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“…4 To date, most techniques for exciton storage rely on strong electric fields which dissociate the exciton confined in the nanostructure. This was, e.g., the case for excitons in quantum wells, 1,5 natural quantum dots (QDs), 6 quantum dot molecules, 3 quantum posts 7 and rods, 8 or quantum rings. 9 Recently, however, Simonin and co-workers studied the behavior of excitons in semiconductor quantum rings subject to perpendicular magnetic and in-plane electric fields.…”

mentioning

confidence: 99%

Exciton storage in type-II quantum dots using the optical Aharonov-Bohm effect

Climente

Planelles

2014

Applied Physics Letters

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We investigate the bright-to-dark exciton conversion efficiency in type-II quantum dots subject to a perpendicular magnetic field. To this end, we take the exciton storage protocol recently proposed by Simonin and co-workers [Phys. Rev. B 89, 075304 (2014)] and simulate its coherent dynamics. We confirm the storage is efficient in perfectly circular structures subject to weak external electric fields, where adiabatic evolution is dominant. In practice, however, the efficiency rapidly degrades with symmetry lowering. Besides, the use of excited states is likely unfeasible owing to the fast decay rates. We then propose an adaptation of the protocol which does not suffer from these limitations. Exciton storage in semiconductor nanostructures is a long-pursued goal in condensed matter physics. Potential applications range from optical 1 and quantum 2 memory elements to light retarders for optical communication and smart pixels, 3 allowing image detection, processing, and generation in one semiconductor element. 4 To date, most techniques for exciton storage rely on strong electric fields which dissociate the exciton confined in the nanostructure. This was, e.g., the case for excitons in quantum wells, 1,5 natural quantum dots (QDs), 6 quantum dot molecules, 3 quantum posts 7 and rods, 8 or quantum rings. 9 Recently, however, Simonin and co-workers studied the behavior of excitons in semiconductor quantum rings subject to perpendicular magnetic and in-plane electric fields. 10 Based on their stationary results, they envisaged a protocol for exciton storage through a sequence of magnetic flux and electric field modulations. The underlying idea is that the initially bright exciton (envelope angular momentum L ¼ 0) is transformed into a dark one (L ¼ 1) by means of the AharonovBohm (AB) optical effect. 11 As opposed to previous protocols, here electron-hole recombination is prevented by angular momentum selection rules. The exciton is then expected to remain bound and no strong electric fields are needed.In this work, we extend the study of the exciton storage mechanism proposed in Ref. 10 by simulating the corresponding dynamics. This allows us to assess on the feasibility of the adiabatic or diabatic steps required by the protocol. The exciton storage protocol conceived in Ref. 10 was originally proposed for InGaAs quantum rings with slightly polarized electron and holes, where the optical AB effect should be observable. For convenience, however, we propose using type-II ZnTe/ZnSe QDs instead. 12 Stacks of such QDs have been fabricated and studied by Sellers and co-workers. 13 They found that the hole in these structures is localized inside the dot, while the electron is outside, orbiting radially around the dot, bound by Coulomb attraction. This is illustrated schematically in Fig. 1(a), which shows side and top views of the system. We note that type-II QDs present two clear advantages with respect to InGaAs rings. First, the difference between electron and hole radii, jR e À R h j, is much larger. As a result, so is...

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Room-Temperature Exciton Storage in Elongated Semiconductor Nanocrystals

Cited by 112 publications

References 30 publications

Exciton storage in CdSe/CdS tetrapod semiconductor nanocrystals: Electric field effects on exciton and multiexciton states

Exciton storage in CdSe/CdS tetrapod semiconductor nanocrystals: Electric field effects on exciton and multiexciton states

Photochemical Oxidative Growth of Iridium Oxide Nanoparticles on CdSe@CdS Nanorods

Exciton storage in type-II quantum dots using the optical Aharonov-Bohm effect

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