Temperature dependent recombination dynamics in InP/ZnS colloidal nanocrystals

Shirazi, Roza; Kopylov, Oleksii; Kovács, András; Kardynał, Beata

doi:10.1063/1.4749276

Cited by 13 publications

(9 citation statements)

References 19 publications

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“…CW VTPL data for the InP, InP/F, and InP/Cd NCs all show decreasing intensities with increasing temperature, consistent with the presence of thermally activated nonradiative decay in all three samples. Similar CW data have been reported elsewhere for unshelled InP NCs, and in fact, most VTPL studies have focused on time-averaged data of shelled InP NC samples, ,,,,,− but it is challenging to deduce any information about bright state population from such CW data. We conclude that the simple surface modifications described here can eliminate nonradiative recombination to a sufficient extent that these NCs behave photophysically similar to InP/ZnS and InP/ZnSe core/shell NCs with relatively thick passivating shells.…”

Section: Resultssupporting

confidence: 70%

“…Beyond their effect on InP NC PLQYs, the surface modifications described here also have interesting effects on other aspects of the NC PL. For example, the data show that the energy of the NC’s first excitonic transition can be tuned in either direction by post-synthetic surface annealing with divalent cations, as detailed previously. , Less obvious is the observation that such submonolayer surface modification manifests itself in distinctive VTPL characteristics previously only observed with InP/ZnS , and InP/ZnSe core/shell NCs involving relatively thick passivating shells. Specifically, the InP/Cd and InP/F NCs show the unusual combination of decreasing short-time PL decay times but increasing short-time PL intensities with increasing temperature, and the data very closely resemble those of the thick-shelled InP NCs reported previously, where this temperature dependence was identified as a signature of thermal dark-bright exciton population equilibration .…”

Section: Resultsmentioning

confidence: 53%

“…g ., Figures and ) indicate the presence of very deep hole traps. Instead, given the well-documented precedent of electronic dark-bright energy splittings stemming from carrier exchange interactions in core/shell InP NCs, ,, we prefer this interpretation of the data in Figures and . It is also noteworthy that this transformation with surface modification is only apparent from VTPL data collected in the time domain.…”

Section: Resultsmentioning

confidence: 99%

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Effects of Surface Chemistry on the Photophysics of Colloidal InP Nanocrystals

et al. 2019

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Indium phosphide (InP) semiconductor nanocrystals (NCs) provide a promising alternative to traditional heavy-metal-based luminescent materials for lighting and display technologies, and implementation of InP NCs in consumer products is rapidly increasing. As-synthesized InP NCs typically have very low photoluminescence quantum yields (PLQY), however. Although empirical methods have led to NCs with near-unity PLQYs, a fundamental understanding of how specific synthetic and post-synthetic protocols can alter the electronic landscape of InP NCs is still lacking. Here, we have studied a series of homologous InP NCs prepared from InP clusters using a combination of room-temperature and low-temperature time-resolved spectroscopies to elucidate how specific charge-carrier trapping processes are affected when various surface modifications are performed. The data allow identification of large PLQY increases that occur specifically through elimination of surface electron traps and provide a rationale for understanding the microscopic origins of this trap suppression in terms of elimination of undercoordinated surface In3+ ions. Despite essentially complete elimination of surface electron trapping when surface In3+ is addressed, hole trapping still exists. This hole trapping is shown to be partially suppressed by even very thin shell growth, attributable to elimination of undercoordinated surface phosphides. We also observe signatures of bright-dark excitonic splitting in InP NCs with only submonolayer surface coverage of select additives (divalent Lewis acids or fluoride anions)−signatures that have only been previously observed in thick-shelled InP NCs. Together, these synthetic and spectroscopic results improve our understanding of relationships between specific InP NC surface chemistries and the resulting NC photophysics.

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Section: Resultssupporting

confidence: 70%

Section: Resultsmentioning

confidence: 53%

Section: Resultsmentioning

confidence: 99%

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Effects of Surface Chemistry on the Photophysics of Colloidal InP Nanocrystals

et al. 2019

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“…Importantly, both experimental and theoretical efforts have begun to explore the fine structure of sustainable materials. On the experimental side, the nature of dark and bright exciton states corresponding to spin-allowed and forbidden transitions, respectively, has been investigated with temperature-dependent PL decay measurements for InP/ZnS, 250 ZnSe 251 and Si 252 NCs. Meanwhile, atomistic pseudopotential calculations have investigated the relationship between the magnitude of the bright/dark exciton splitting and the size of GaAs, InAs and Si QDs.…”

Section: Sustainable Future Quantum Technology With Colloidal Ncsmentioning

confidence: 99%

A sustainable future for photonic colloidal nanocrystals

2015

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Colloidal nanocrystals - produced in a growing variety of shapes, sizes and compositions - are rapidly developing into a new generation of photonic materials, spanning light emitting as well as energy harvesting applications. Precise tailoring of their optoelectronic properties enables them to satisfy disparate application-specific requirements. However, the presence of toxic heavy metals such as cadmium and lead in some of the most mature nanocrystals is a serious drawback which may ultimately preclude their use in consumer applications. Although the pursuit of non-toxic alternatives has occurred in parallel to the well-developed Cd- and Pb-based nanocrystals, synthetic challenges have, until recently, curbed progress. In this review, we highlight recent advances in the development of heavy-metal-free nanocrystals within the context of specific photonic applications. We also describe strategies to transfer some of the advantageous nanocrystal features such as shape control to non-toxic materials. Finally, we present recent developments that have the potential to make substantial impacts on the quest to attain a balance between performance and sustainability in photonics.

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“…suggested that at cryogenic temperatures the PL stems from a spin-forbidden dark exciton state. More recent work on the temperature dependence of the PL decay of a commercial sample of InP/ZnS NCs with a diameter of 3.5 nm seems to support this assumption, but remains restricted because of the presence of trapping sites at energies comparable to the fine structure energy splitting . To the best of our knowledge systematic studies of the exciton fine structure and exciton recombination dynamics are still missing for colloidal InP-based NCs.…”

mentioning

confidence: 99%

Band-Edge Exciton Fine Structure and Recombination Dynamics in InP/ZnS Colloidal Nanocrystals

et al. 2016

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We report on a temperature-, time-, and spectrally resolved study of the photoluminescence of type-I InP/ZnS colloidal nanocrystals with varying core size. By studying the exciton recombination dynamics we assess the exciton fine structure in these systems. In addition to the typical bright-dark doublet, the photoluminescence stems from an upper bright state in spite of its large energy splitting (∼100 meV). This striking observation results from dramatically lengthened thermalization processes among the fine structure levels and points to optical-phonon bottleneck effects in InP/ZnS nanocrystals. Furthermore, our data show that the radiative recombination of the dark exciton scales linearly with the bright-dark energy splitting for CdSe and InP nanocrystals. This finding strongly suggests a universal dangling bonds-assisted recombination of the dark exciton in colloidal nanostructures.

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Temperature dependent recombination dynamics in InP/ZnS colloidal nanocrystals

Cited by 13 publications

References 19 publications

Effects of Surface Chemistry on the Photophysics of Colloidal InP Nanocrystals

Effects of Surface Chemistry on the Photophysics of Colloidal InP Nanocrystals

A sustainable future for photonic colloidal nanocrystals

Band-Edge Exciton Fine Structure and Recombination Dynamics in InP/ZnS Colloidal Nanocrystals

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