Experimental tests of effective mass and atomistic approaches to quantum dot electronic structure: Ordering of electronic states

Sewall, Samuel L.; Cooney, Ryan R.; Kambhampati, Patanjali

doi:10.1063/1.3157269

Cited by 48 publications

(52 citation statements)

References 25 publications

(50 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Regardless of the theoretical approach, it is known that these higher lying transitions have significant P electron character. 3,4,15,45,46 It is entirely consistent to attribute this enhanced gain bandwidth to the capacity of the 1P e -1P 3/2 and 1S e -2S 1/2 excitonic states to contain higher-order charge distributions. This mixture of higher-order charge distributions, accessible due to the sixfold degenerate 1P e state, results in a mixture of available transition energies for the emitting state due to confinement enhanced multiexcitonic interactions.…”

Section: Gain Tailoring In Semiconductor Quantum Dotsmentioning

confidence: 83%

“…46 Here we will continue to denote these transitions as 1P e -1P 3/2 and 1S e -2S 1/2 , for the sake of maintaining convention with commonly used notation in the experimental literature. Regardless of the theoretical approach, it is known that these higher lying transitions have significant P electron character.…”

Section: Gain Tailoring In Semiconductor Quantum Dotsmentioning

confidence: 99%

See 1 more Smart Citation

State-resolved manipulations of optical gain in semiconductor quantum dots: Size universality, gain tailoring, and surface effects

Cooney

Sewall

Sagar

et al. 2009

The Journal of Chemical Physics

Self Cite

130

View full text Add to dashboard Cite

Optical gain in strongly confined colloidal semiconductor quantum dots is measured using state resolved pump/probe spectroscopy. Though size tunable optical amplification has been previously reported for these materials, the influence of confinement enhanced multiexcitonic interactions has limited prior demonstrations to specific particle sizes or host media. Here we show that the influence of the interfering multiexcitonic interactions, and hence the development of optical gain, is dependent on the identity of the initially prescribed excitonic state. By maintaining a constant excitonic state in the size tunable electronic structure of these materials, we recover the predicted universal development of optical gain, reflected by size-independent occupation thresholds, and differential gains. In addition, we explicitly compare the influence of surface passivation on the development and lifetime of the optical gain. Furthermore, we introduce a general, state-resolved pumping scheme which enables control over the optical gain spectrum. The capacity to manipulate the optical gain spectra of these spherically confined systems is evident in both the measured stimulated emission and amplified spontaneous emission. We anticipate that state-resolved optical excitation will be a useful method of enabling the development and manipulation of optical gain in any quantized nanostructure.

show abstract

Section: Gain Tailoring In Semiconductor Quantum Dotsmentioning

confidence: 83%

Section: Gain Tailoring In Semiconductor Quantum Dotsmentioning

confidence: 99%

State-resolved manipulations of optical gain in semiconductor quantum dots: Size universality, gain tailoring, and surface effects

Cooney

Sewall

Sagar

et al. 2009

The Journal of Chemical Physics

Self Cite

130

View full text Add to dashboard Cite

show abstract

“…Qualitative discrepancies between the predictions of the effective mass model and results from quantum chemical calculations have been described previously. 50,51 The idea that highly energetic electron-hole pairs are bulk-like and largely localized on a length scale smaller than that of the quantum dot has been put forward previously for PbS 52 and PbSe 53 QDs. Experiments on CdSe/CdS dot-in-rod structures have also been interpreted to show long-lived exciton localization in the CdS shell.…”

Section: Figure 7 Experimental (Black) and Calculated (Red) Frequencmentioning

confidence: 99%

Electron–Phonon Coupling in CdSe/CdS Core/Shell Quantum Dots

et al. 2015

View full text Add to dashboard Cite

Resonance Raman spectra and excitation profiles have been measured and semiquantitatively modeled for core/shell quantum dots consisting of 2.7 nm diameter zincblende CdSe cores and thin (0.5 nm) or thick (1.6 nm) CdS shells. The Raman spectra show previously reported trends of increased peak frequency for both the CdSe and the CdS longitudinal optical (LO) phonons with increasing shell thickness. We also find a strong dependence of the peak CdS frequency on excitation energy and a large discrepancy between the experimental frequency of the CdSe+CdS combination band and the sum of the corresponding fundamental frequencies. This suggests that the dominant transitions at high excitation energies are localized on either the CdSe core or the CdS shell and thereby cannot enhance combination band transitions between core and shell. The CdS to CdSe Raman intensity ratios at high excitation energies further support this picture. The electron-phonon coupling for the CdSe LO phonon in the lowest excitonic transition is slightly weaker in the core/shell structures than in pure CdSe quantum dots, contrary to expectations for the Fröhlich coupling mechanism. Possible explanations for this discrepancy are discussed.

show abstract

“…50 At room temperature it has been commonly observed that the decays of B1 and B2 mirror each other, implicating occupation of the 1S e state as a common denominator. 19,20,61 In contrast, in our low-temperature measurements the lifetime of the aggregate B1 bleach is much longer than that of B2 for all samples (Figure 4aÀd and Figure 2eÀh), which cannot be due to a 1S e electron or a dark exciton. We instead attribute the longer life of ARTICLE B1 relative to B2 to the presence of a long-lived hole in the 1S 3/2h state and interpret the decay of the B2 bleach as reflecting the rapid surface trapping of an electron that leaves this hole remaining in the QD core.…”

Section: Resultsmentioning

confidence: 76%

Ultrafast Electron Trapping in Ligand-Exchanged Quantum Dot Assemblies

et al. 2015

View full text Add to dashboard Cite

We use time-integrated and time-resolved photoluminescence and absorption to characterize the low-temperature optical properties of CdSe quantum dot solids after exchanging native aliphatic ligands for thiocyanate and subsequent thermal annealing. In contrast to trends established at room temperature, our data show that at low temperature the band-edge absorptive bleach is dominated by 1S3/2h hole occupation in the quantum dot interior. We find that our ligand treatments, which bring enhanced interparticle coupling, lead to faster surface state electron trapping, a greater proportion of surface-related photoluminescence, and decreased band-edge photoluminescence lifetimes.

show abstract

Experimental tests of effective mass and atomistic approaches to quantum dot electronic structure: Ordering of electronic states

Cited by 48 publications

References 25 publications

State-resolved manipulations of optical gain in semiconductor quantum dots: Size universality, gain tailoring, and surface effects

State-resolved manipulations of optical gain in semiconductor quantum dots: Size universality, gain tailoring, and surface effects

Electron–Phonon Coupling in CdSe/CdS Core/Shell Quantum Dots

Ultrafast Electron Trapping in Ligand-Exchanged Quantum Dot Assemblies

Contact Info

Product

Resources

About