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Enhancement of Charge Transfer and Quenching of Photoluminescence of Capped CdS Quantum Dots.

Mehata MS - Sci Rep (2015)

Bottom Line: An external electric field of variable strength of 0.2-1.0 MV cm(-1) was applied to the sample of capped CdS Q-dots doped in a poly(methyl methacrylate) (PMMA) films.PL of capped CdS Q-dots is significantly quenched in presence of external electric field.Thus, understanding the CT character and field-induced PL quenching of CdS Q-dots is important for photovoltaic, LEDs and biological applications.

View Article: PubMed Central - PubMed

Affiliation: Laser-Spectroscopy Laboratory, Department of Applied Physics, Delhi Technological University, Bawana Road, Delhi 110042, INDIA.

ABSTRACT
Quantum dots (Q-dots) of cadmium sulfide (CdS) with three different capping ligands, 1-butanethiol (BT), 2-mercaptoethanol (ME) and benzyl mercaptan (BM) have been investigated. An external electric field of variable strength of 0.2-1.0 MV cm(-1) was applied to the sample of capped CdS Q-dots doped in a poly(methyl methacrylate) (PMMA) films. Field-induced changes in optical absorption of capped CdS Q-dots were observed in terms of purely the second-derivative of the absorption spectrum (the Stark shift), indicating an enhancement in electric dipole moment following transition to the first exciton state. The enhancement depends on the shape and size of the Q-dots prepared using different capping ligands. Field induced-change in photoluminescence (PL) reveals similar changes, an enhancement in charge-transfer (CT) character in exciton state. PL of capped CdS Q-dots is significantly quenched in presence of external electric field. The strong field-induced quenching occurs as a result of the increased charge separation resulting exciton dissociation. Thus, understanding the CT character and field-induced PL quenching of CdS Q-dots is important for photovoltaic, LEDs and biological applications.

No MeSH data available.


Related in: MedlinePlus

Electro-photoluminescence (E-PL) and photoluminescence (PL) spectra of BM-capped CdS Q-dots embedded in a PMMA film obtained with field strength of 0.2–0.8 MV cm−1 in vacuum near 295 K.Excitation wavelength was 411 nm.
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f6: Electro-photoluminescence (E-PL) and photoluminescence (PL) spectra of BM-capped CdS Q-dots embedded in a PMMA film obtained with field strength of 0.2–0.8 MV cm−1 in vacuum near 295 K.Excitation wavelength was 411 nm.

Mentions: Figures 4, 5, 6 show photoluminescence and electro-photoluminescence spectra of capped CdS Q-dots doped in a PMMA films. In all cases, the PL spectrum shows a broad band in the range of 420–800 nm. The position of the band maximum is different for different Q-dots; this is because of the distinct shape and size of Q-dots. The band maxima are at around 626 nm for BT, 566 nm for ME and 564 nm for BM capped CdS Q-dots. The large spectral width of the observed PL band is caused by inhomogeneous broadening due to a variation in particle size and broadening due to electron-phonon coupling23, whereas the large Stoke’s shift indicates that the emitting state is not the same as the optically excited state. In case of ME capped CdS Q-dots doped in a PMMA film, a comparatively smaller PL intensity was observed and the band is also dominated by a typical band appeared at shorter wavelength side in the range of 400–500 nm, the intensity of such a spurious band is very small when the PL spectra measured in solution8 however, we are unable to comment exactly on it at present.


Enhancement of Charge Transfer and Quenching of Photoluminescence of Capped CdS Quantum Dots.

Mehata MS - Sci Rep (2015)

Electro-photoluminescence (E-PL) and photoluminescence (PL) spectra of BM-capped CdS Q-dots embedded in a PMMA film obtained with field strength of 0.2–0.8 MV cm−1 in vacuum near 295 K.Excitation wavelength was 411 nm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4499802&req=5

f6: Electro-photoluminescence (E-PL) and photoluminescence (PL) spectra of BM-capped CdS Q-dots embedded in a PMMA film obtained with field strength of 0.2–0.8 MV cm−1 in vacuum near 295 K.Excitation wavelength was 411 nm.
Mentions: Figures 4, 5, 6 show photoluminescence and electro-photoluminescence spectra of capped CdS Q-dots doped in a PMMA films. In all cases, the PL spectrum shows a broad band in the range of 420–800 nm. The position of the band maximum is different for different Q-dots; this is because of the distinct shape and size of Q-dots. The band maxima are at around 626 nm for BT, 566 nm for ME and 564 nm for BM capped CdS Q-dots. The large spectral width of the observed PL band is caused by inhomogeneous broadening due to a variation in particle size and broadening due to electron-phonon coupling23, whereas the large Stoke’s shift indicates that the emitting state is not the same as the optically excited state. In case of ME capped CdS Q-dots doped in a PMMA film, a comparatively smaller PL intensity was observed and the band is also dominated by a typical band appeared at shorter wavelength side in the range of 400–500 nm, the intensity of such a spurious band is very small when the PL spectra measured in solution8 however, we are unable to comment exactly on it at present.

Bottom Line: An external electric field of variable strength of 0.2-1.0 MV cm(-1) was applied to the sample of capped CdS Q-dots doped in a poly(methyl methacrylate) (PMMA) films.PL of capped CdS Q-dots is significantly quenched in presence of external electric field.Thus, understanding the CT character and field-induced PL quenching of CdS Q-dots is important for photovoltaic, LEDs and biological applications.

View Article: PubMed Central - PubMed

Affiliation: Laser-Spectroscopy Laboratory, Department of Applied Physics, Delhi Technological University, Bawana Road, Delhi 110042, INDIA.

ABSTRACT
Quantum dots (Q-dots) of cadmium sulfide (CdS) with three different capping ligands, 1-butanethiol (BT), 2-mercaptoethanol (ME) and benzyl mercaptan (BM) have been investigated. An external electric field of variable strength of 0.2-1.0 MV cm(-1) was applied to the sample of capped CdS Q-dots doped in a poly(methyl methacrylate) (PMMA) films. Field-induced changes in optical absorption of capped CdS Q-dots were observed in terms of purely the second-derivative of the absorption spectrum (the Stark shift), indicating an enhancement in electric dipole moment following transition to the first exciton state. The enhancement depends on the shape and size of the Q-dots prepared using different capping ligands. Field induced-change in photoluminescence (PL) reveals similar changes, an enhancement in charge-transfer (CT) character in exciton state. PL of capped CdS Q-dots is significantly quenched in presence of external electric field. The strong field-induced quenching occurs as a result of the increased charge separation resulting exciton dissociation. Thus, understanding the CT character and field-induced PL quenching of CdS Q-dots is important for photovoltaic, LEDs and biological applications.

No MeSH data available.


Related in: MedlinePlus