Dynamics of electron-hole pair recombination in semiconductor clusters

O’Neil, Michael; Marohn, John A.; McLendon, George

doi:10.1021/j100373a089

Cited by 307 publications

(206 citation statements)

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“…In contrast, in nanocrystalline TiO 2 , recombination rates increase as the particle size decreases, and rapid surface recombination becomes the dominant relaxation process. 44,49 However, this interpretation does not fully explain the slower hole dynamics, and differences in the relaxation dynamics may arise from other physical characteristics that depend on nanosheet size. Our interpretation of the trapped hole spectrum suggested that the concentration of trapped electrons was initially larger than the trapped hole concentration.…”

Section: Trapping and Recombinationmentioning

confidence: 99%

Ultrafast Carrier Dynamics in Exfoliated and Functionalized Calcium Niobate Nanosheets in Water and Methanol

et al. 2008

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We have characterized the initial charge carrier trapping and recombination processes in suspensions of exfoliated calcium niobate nanosheets derived from the Dion Jacobsen phase KCa 2 Nb 3 O 10 . Niobate nanosheets have previously been found to catalyze hydrogen generation in photochemical water-splitting reactions. Photogenerated charge carriers relaxed with second-order kinetics on a sub-nanosecond time scale that depended on the nanosheet size. Methanol was used as a sacrificial electron donor to separate the electron and hole dynamics, and the photo-oxidation dynamics was found to directly compete with electron-hole recombination. Absorption spectra for trapped carriers were determined and used to separately analyze the trapped electron and hole dynamics in [H 1-x Ca 2 Nb 3 O 10 ]x-(x ) 0.15-0.20) sheets in water. Surface modification by 3-aminopropyl(trimethoxy)silane was found to quench trapped carrier absorptions, resulting in an observed optical gain.

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Section: Trapping and Recombinationmentioning

confidence: 99%

Ultrafast Carrier Dynamics in Exfoliated and Functionalized Calcium Niobate Nanosheets in Water and Methanol

et al. 2008

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“…Such a behavior suggests that both the green and orange luminescence are caused by donor-acceptor recombination. 51,52 The fit results for these decay profiles are listed in Table 3. With the detection wavelength increasing from 560 nm to 680 nm, the fast lifetime is almost unchanged while the slow lifetime …”

Section: Carrier Dynamics Of Zns Nanocrystalsmentioning

confidence: 99%

Visible emission characteristics from different defects of ZnS nanocrystals

Wang

Shi

Feng

et al. 2011

Phys. Chem. Chem. Phys.

171

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Various sized ZnS nanocrystals were prepared by treatment under H 2 S atmosphere. Resonance Raman spectra indicate that the electron-phonon coupling increases with increasing the size of ZnS. Surface and interfacial defects are formed during the treatment processes. Blue, green and orange emissions are observed for these ZnS. The blue emission (430 nm) from ZnS without treatment is attributed to surface states. ZnS sintered at 873 K displays orange luminescence (620 nm) while ZnS treated at 1173 K shows green emission (515 nm). The green luminescence is assigned to the electron transfer from sulfur vacancies to interstitial sulfur states, and the orange emission is caused by the recombination between interstitial zinc states and zinc vacancies. The lifetimes of the orange emission are much slower than that of the green luminescence and sensitively dependent on the treatment temperature. Controlling defect formation makes ZnS a potential material for photoelectrical applications.

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“…4 Increased ionic bonding character within a bulk crystal leads to successively shallower surface traps. 15 For the relatively ionic II-VI class of materials, the case of surface states on bulk ZnO has been well studied.…”

Section: B Temperature Dependent Pl: Activation Barriersmentioning

confidence: 99%

“…A three-state model has been successfully utilized by a number of research groups to explain various aspects of the PL spectra of certain II-VI nanocrystals. [4][5][6] In the model, the three ''states'' correspond to the valence and conduction band ͑VB and CB͒ manifolds, and localized surface states. Although the details of II-VI semiconductor nanocrystals are quite complex and not completely worked out, 7,8 certain basic facts have emerged.…”

Section: Introductionmentioning

confidence: 99%

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Photophysics of size-selected InP nanocrystals: Exciton recombination kinetics

Kim

Wolters

Heath

1996

The Journal of Chemical Physics

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We report here on the size-dependent kinetics of exciton recombination in a III-V quantum dot system, InP. The measurements reported include various frequency dependent quantum yields as a function of temperature, frequency dependent luminescence decay curves, and time-gated emission spectra. This data is fit to a three-state quantum model which has been previously utilized to explain photophysical phenomena in II-VI quantum dots. The initial photoexcitation is assumed to place an electron in a ͑delocalized͒ bulk conduction band state. Activation barriers for trapping and detrapping of the electron to surface states, as well as activation barriers for surface-state radiationless relaxation processes are measured as a function of particle size. The energy barrier to detrapping is found to be the major factor limiting room temperature band-edge luminescence. This barrier increases with decreasing particle size. For 30 Å particles, this barrier is found to be greater than 6 kJ/mol-a barrier which is more than an order of magnitude larger than that previously found for 32 Å CdS nanocrystals.

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Dynamics of electron-hole pair recombination in semiconductor clusters

Cited by 307 publications

References 1 publication

Ultrafast Carrier Dynamics in Exfoliated and Functionalized Calcium Niobate Nanosheets in Water and Methanol

Ultrafast Carrier Dynamics in Exfoliated and Functionalized Calcium Niobate Nanosheets in Water and Methanol

Visible emission characteristics from different defects of ZnS nanocrystals

Photophysics of size-selected InP nanocrystals: Exciton recombination kinetics

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