Ultrafast carrier dynamics in CuInS2 quantum dots

Sun, Jianhui; Zhu, Dehua; Zhao, Jingbo; Ikezawa, Michio; Wang, Xiuying; Masumoto, Yasuaki

doi:10.1063/1.4862274

Cited by 43 publications

(73 citation statements)

References 18 publications

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“…The relaxation of the 1S states is faster in smaller QDs with larger density of carriers at surface, because the surface trapping rate is proportional to the existing probability of carriers at the QD surface. 28,39 Therefore, surface traps provide local sites for fast relaxation of the photoexcited excitons, mainly resulting in a short PL-lifetime in smaller CIS QDs with shorter-wavelength emission. We investigated the PL kinetics of the CIS QDs before and after shell growth to further understand the luminescence mechanism underlying the extrinsic impurities, as shown in Fig.…”

Section: Time-resolved Pl Spectroscopy Of Cis Qds and Cis/zns Core/shmentioning

confidence: 99%

“…In our previous work, we found that the electron trapping at surface defects increased with decreasing the QD size which significantly reduced the carrier lifetimes of small CIS QDs. 28 The different relaxation behavior was due to the size inhomogeneity in CIS QDs. The relaxation of the carriers is faster in smaller QDs because of the larger density of states of electrons and holes at the surface.…”

Section: Introductionmentioning

confidence: 99%

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Photocarrier recombination dynamics in ternary chalcogenide CuInS₂ quantum dots

Sun

Ikezawa

Wang

et al. 2015

Phys. Chem. Chem. Phys.

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Photocarrier recombination dynamics in ternary chalcogenide CuInS2 quantum dots (CIS QDs) was studied by means of femtosecond transient-absorption (TA) and nanosecond time-resolved photoluminescence (PL) spectroscopy. Under strong excitation, the TA dynamics in CIS QDs is well described by a simple rate equation including single-carrier trapping, free-to-bound recombination, and trap-assisted Auger recombination. Under weak excitation, on the other hand, the PL decays of the QDs are composed of a short-lived component caused by surface trapping and a long-lived one caused by free-to-bound recombination. It is found that the surface trapping accelerates markedly with decreasing QD size while the free-to-bound radiative recombination hardly depends on the QD size. Besides this, we observed both a decrease in the PL lifetimes and a dynamic spectral redshift, which are attributed to the surface trapping and the coexistent inhomogeneous broadening in CIS QDs. The spectral redshift becomes less pronounced in CIS/ZnS core/shell QDs because of the suppression of the fast nonradiative recombination caused by the passivation of the surface traps. These results give clear evidence that the free-to-bound model is appropriate for interpreting the optical properties of CIS QDs.

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Section: Time-resolved Pl Spectroscopy Of Cis Qds and Cis/zns Core/shmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Photocarrier recombination dynamics in ternary chalcogenide CuInS₂ quantum dots

Sun

Ikezawa

Wang

et al. 2015

Phys. Chem. Chem. Phys.

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“…In addition to off-stoichiometry defects in the bulk, surface states are also found to play a significant role in carrier trapping for CuInS 2 QDs, 4 , 16 , 24 which reduces charge separation efficiencies in related photovoltaic and photocatalytic devices. Coating QDs with another material to form core/shell hetero QDs has been an effective approach to mitigating surface trapping states.…”

Section: Introductionmentioning

confidence: 99%

Quasi-type II CuInS₂/CdS core/shell quantum dots

Liang

Kong

et al. 2016

Chem. Sci.

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“…The photoluminescence of Cu-rich CIS QDs originates from the recombinations of electrons and holes trapped in the defect states (Fig. [48][49][50] Furthermore, we measured the PLQY of NIRemitting QDs, which have an emission peak at 718.6 nm, using rhodamine B 49 to conrm the reliability of the PLQY determined with rhodamine 6G. 43 The PLQY of the QDs was determined by comparing the total emission intensity of the QDs with that of rhodamine 6G at an excitation wavelength of 500 nm.…”

Section: Resultsmentioning

confidence: 99%

Highly luminescent, off-stoichiometric Cu_xIn_yS₂/ZnS quantum dots for near-infrared fluorescence bio-imaging

et al. 2015

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Quantum dots (QDs) are very attractive for in vivo bio-imaging and therapeutic applications due to their relatively large absorption coefficient, high quantum yield, low level of photo bleaching, and large Stokes shift. However, two technical issues need to be resolved before they can be practically applied to in vivo bio-imaging applications: ensuring both reduced toxicity and efficient emission in the near-infrared (NIR) frequency range. Here we report a simple and reliable method to synthesize highly luminescent, NIRemitting Cu x In y S 2 /ZnS (CIS/ZnS) core-shell QDs for deep-tissue bio imaging applications. Offstoichiometric effects are utilized with 1-dodecanethiol as a reaction medium for thermolytic synthesis.The most important finding in our work is that at a high Cu/In ratio, the emission spectrum of CIS/ZnS QDs can be tuned to NIR frequencies with a high quantum yield up to approximately 65%. The maximum emission wavelengths of the synthesized QDs are 589 nm (QD 589 ) and 726 nm (QD 726 ) at a Cu/In ratio of 0.25 and of 1.8, respectively. Their feasibility for optical bio-imaging in a deep-tissue condition is investigated by the intramuscular injection of QD-loaded polymer microspheres in a mouse model. Our results show that more than 30% of the original emission of the QD 726 can be detected through biological tissue of 0.9 cm, whereas emission from the QD 589 is not detectable. Our investigation on the offstoichiometric effects of CIS QDs will contribute to the development of highly luminescent, NIR-emitting, cadmium-free QDs in the areas of tissue-level imaging, sensing, and therapeutics. † Electronic supplementary information (ESI) available: Size distribution histograms of the CIS QDs (Fig. S1); comparison of PLQY with a previous work (Fig. S2); the original curve of absorption spectra of the CIS QDs (Fig. S3); size distribution histograms of the CIS/ZnS QDs (Fig. S4); SEM images of the QD-loaded PMMA microspheres (Fig. S5). See

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Ultrafast carrier dynamics in CuInS2 quantum dots

Cited by 43 publications

References 18 publications

Photocarrier recombination dynamics in ternary chalcogenide CuInS₂ quantum dots

Photocarrier recombination dynamics in ternary chalcogenide CuInS₂ quantum dots

Quasi-type II CuInS₂/CdS core/shell quantum dots

Highly luminescent, off-stoichiometric Cu_xIn_yS₂/ZnS quantum dots for near-infrared fluorescence bio-imaging

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Ultrafast carrier dynamics in CuInS2 quantum dots

Cited by 43 publications

References 18 publications

Photocarrier recombination dynamics in ternary chalcogenide CuInS2 quantum dots

Photocarrier recombination dynamics in ternary chalcogenide CuInS2 quantum dots

Quasi-type II CuInS2/CdS core/shell quantum dots

Highly luminescent, off-stoichiometric CuxInyS2/ZnS quantum dots for near-infrared fluorescence bio-imaging

Contact Info

Product

Resources

About

Photocarrier recombination dynamics in ternary chalcogenide CuInS₂ quantum dots

Photocarrier recombination dynamics in ternary chalcogenide CuInS₂ quantum dots

Quasi-type II CuInS₂/CdS core/shell quantum dots

Highly luminescent, off-stoichiometric Cu_xIn_yS₂/ZnS quantum dots for near-infrared fluorescence bio-imaging