Excitation Energy Dependence of Semiconductor Nanocrystal Emission Quantum Yields

Zhang, Zhuoming; Zhang, Shubin; Gushchina, Irina; Guo, Tianle; Brennan, Michael C.; Pavlovetc, Ilia M.; Grusenmeyer, Tod A.; Kuno, Masaru

doi:10.1021/acs.jpclett.1c00811

Cited by 9 publications

(16 citation statements)

References 51 publications

(149 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

Section: Results and Discussionmentioning

confidence: 99%

“…The investigation of excitation energy-dependent emission in nanostructures is of paramount significance to elucidate the material-specific origin to design the landscape toward their potential applications. 49 The epicenter of this unusual physical phenomenon has been traced to the nonradiative relaxation of the charge carriers, intraband or phonon coupling, and Augermediated processes. The phenomenon of excitation energy- dependent emission (EDE) can also be named the terminologies such as red-edge effect (REE), edge excitation shift (EES), edge excitation red shift (EERS), or the red-edge excitation shift (REES).…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Critical Crystallographic Transition in Violation of Kasha’s Rule of Size-Specific ZnO Quantum Dots

Debnath

Pal

Chatterjee

et al. 2023

Crystal Growth & Design

View full text Add to dashboard Cite

Investigation of the intrinsic relationship between crystallography and electronic properties may provide an avenue to unravel the photophysical aspects of semiconductor nanostructures. Since the 1980s, semiconducting materials at the nanoscale dimensions have been of immense scientific interest because of the unique quantum characteristics beyond a particular size limit. Prudent advances in the synthetic strategies of naked ZnO quantum dots have offered the opportunity to imbue the structure−property relationship of nanostructured systems. Seven size-specific ZnO nanospheres have been synthesized through alkaline hydrolysis of the precursor salt in the presence of alcohol in the reaction medium. The photoluminescence behavior of colloidal dispersion of ZnO nanoparticles has been studied as a function of excitation wavelength with a periodic interval of 10 nm in the range of 290−430 nm. It has been observed that changes in the excitation wavelength shift the emission spectrum in a regular manner independent of the size of ZnO particles under investigation. The empirical proposition in the framework of Kasha's rule has been established as a milestone of spectroscopy, being validated in tens of thousands of fluorophore systems; meanwhile, although obscure, anomalous cases have also been observed both in molecular and nanoscale systems. Crystallographic analysis has shown that there occurs a structural transition that determines the localization of electronic energy levels in the experimental size range of the ZnO particles. Therefore, the salient feature of physical significance is that crystallographic transition appears to exhibit the excitation wavelength-dependent shift of the photoluminescence maximum and is therefore the violation of Kasha's rule for the ZnO quantum dots.

show abstract

Section: Results and Discussionmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Critical Crystallographic Transition in Violation of Kasha’s Rule of Size-Specific ZnO Quantum Dots

Debnath

Pal

Chatterjee

et al. 2023

Crystal Growth & Design

View full text Add to dashboard Cite

show abstract

“…3 c and d, the ratio of the LH bleaching intensity is consistently larger, for similar initial carrier density, for the 2.72 eV pump than the 3.50 eV pump. The stronger intensity of excitonic bleaching of both HH and LH transitions under 2.72 eV photon energy excitation may be explained by higher effective quantum yield for bleaching with less energetic photons 38 , although reports of the energy-dependent quantum yield are contested 39 – 42 . A second effect accompanying more intense photoexcitation is captured in Fig.…”

Section: Resultsmentioning

confidence: 99%

Gain roll-off in cadmium selenide colloidal quantum wells under intense optical excitation

Diroll

Brumberg

Schaller

2022

Sci Rep

View full text Add to dashboard Cite

Colloidal quantum wells, or nanoplatelets, show among the lowest thresholds for amplified spontaneous emission and lasing among solution-cast materials and among the highest modal gains of any known materials. Using solution measurements of colloidal quantum wells, this work shows that under photoexcitation, optical gain increases with pump fluence before rolling off due to broad photoinduced absorption at energies lower than the band gap. Despite the common occurrence of gain induced by an electron–hole plasma found in bulk materials and epitaxial quantum wells, under no measurement conditions was the excitonic absorption of the colloidal quantum wells extinguished and gain arising from a plasma observed. Instead, like gain, excitonic absorption reaches a minimum intensity near a photoinduced carrier sheet density of 2 × 1013 cm−2 above which the absorption peak begins to recover. To understand the origins of these saturation and reversal effects, measurements were performed with different excitation energies, which deposit differing amounts of excess energy above the band gap. Across many samples, it was consistently observed that less energetic excitation results in stronger excitonic bleaching and gain for a given carrier density. Transient and static optical measurements at elevated temperatures, as well as transient X-ray diffraction of the samples, suggest that the origin of gain saturation and reversal is a heating and disordering of the colloidal quantum wells which produces sub-gap photoinduced absorption.

show abstract

“…Barring very few exceptions involving the emission from S 2 etc. , organic fluorophores follow both Kasha’s rule and Vavilov’s rule; however, QDs follow Kasha’s rule but not Vavilov’s rule. − Because of the very broad absorption spectrum of QDs, any EE within this spectrum can give rise to PL. Although the PL max is independent of the EE, molar extinction coefficient (ε) as well as PLQY (ϕ) have been reported to be dependent on EE for QDs (Scheme b). ,,,− Therefore, brightness (= ε·ϕ) is expected to be dependent on the magnitude of EE.…”

mentioning

confidence: 99%

“…Although the molar extinction coefficient is expected to be dependent on EE, PLQY being dependent on EE is a relatively much newer phenomenon. − …”

mentioning

confidence: 99%

Excitation-Energy-Dependent Photoluminescence Quantum Yield is Inherent to Optically Robust Core/Alloy-Shell Quantum Dots in a Vast Energy Landscape

Roy

Ghosh

et al. 2022

J. Phys. Chem. Lett.

View full text Add to dashboard Cite

The importance of alloy-shelling in optically robust Core/Alloy-Shell (CAS) QDs has been described from structural and energetic aspects. Unlike fluorescent dyes, both Core/Shell (CS) and CAS QDs exhibit excitation-energy-dependent photoluminescence quantum yield (PLQY). For both CdSe and InP CAS QDs (with metal- and nonmetal-based alloy-shelling, respectively), with increasing excitation energy, (a) the ultrafast rise-time or relaxation-time to the band-edge increases and (b) the magnitude of the normalized bleach signal decreases. Ultrasensitive single-particle spectroscopic investigation results showed that with decreasing excitation energy, (a) the fraction of ON events increases, (b) the ratio of exciton-detrapping rate/trapping rate increases, and (c) the extent of beneficial hole trapping increases. A relative decrease in PLQY with increasing excitation energy is much less pronounced in CAS QDs than in CS QDs. Unless trap states are removed completely especially in the higher-energy landscape, PLQY will remain inherently dependent on excitation energy for QDs in the vast energy landscape. When reporting the PLQY of QDs, the magnitude of the excitation energy must be mentioned.

show abstract

Excitation Energy Dependence of Semiconductor Nanocrystal Emission Quantum Yields

Cited by 9 publications

References 51 publications

Critical Crystallographic Transition in Violation of Kasha’s Rule of Size-Specific ZnO Quantum Dots

Critical Crystallographic Transition in Violation of Kasha’s Rule of Size-Specific ZnO Quantum Dots

Gain roll-off in cadmium selenide colloidal quantum wells under intense optical excitation

Excitation-Energy-Dependent Photoluminescence Quantum Yield is Inherent to Optically Robust Core/Alloy-Shell Quantum Dots in a Vast Energy Landscape

Contact Info

Product

Resources

About