Quantum-Confined Electron Transitions in CdSe Nanocrystals

2000 ◽  
Vol 642 ◽  
Author(s):  
D. S. Ginger ◽  
A. S. Dhoot ◽  
C. E. Finlayson ◽  
N. C. Greenham
Keyword(s):  
Room Temperature ◽  
Electron State ◽  
Cdse Nanocrystals ◽  
Size Dependent ◽  
Excitonic Absorption ◽  
Electron Transitions ◽  
Delocalized Electron ◽  
Excitonic Transition ◽  
Dependent Absorption ◽  
Absorption Measurements

ABSTRACTWe present quasi-steady-state photoinduced absorption measurements on thin films of colloidal CdSe nanocrystals. We observe an intense, size-dependent absorption peaking in the mid-infrared when the samples are irradiated with visible light. The absorption is accompanied by a bleach in the visible near the position of the first excitonic absorption and persists with a lifetime of milliseconds at room temperature. We characterize the lifetime of the electron state and its cross-section. We attribute this feature to the 1S-1P transition of a delocalized electron. We report a bleaching of the first excitonic transition in electrically excited nanocrystal-based diode structures, and attribute it to charging of the 1S electron state.

Size-Dependent Absorption and Defect States in CdSe Nanocrystals in Various Multilayer Structures

2002 ◽  
Vol 2 (6) ◽  
pp. 645-652 ◽  
Author(s):  
D. Nesheva ◽  
Z. Levi ◽  
Z. Aneva ◽  
I. Zrinscak ◽  
C. Main ◽  
...  
Keyword(s):  
Multilayer Structures ◽  
Cdse Nanocrystals ◽  
Defect States ◽  
Size Dependent ◽  
Dependent Absorption

Electrophoretic Deposition of CdSe Nanocrystals for Photovoltaic Applications

2007 ◽  
Vol 1031 ◽  
Author(s):  
Nathanael Smith ◽  
Kevin J Emmett ◽  
Sandra J Rosenthal
Keyword(s):  
Titanium Dioxide ◽  
Electrophoretic Deposition ◽  
Room Temperature ◽  
Tio2 Thin Film ◽  
Cdse Nanocrystals ◽  
Photovoltaic Devices ◽  
Photovoltaic Applications ◽  
Nanocrystalline Titanium ◽  
Alternative Techniques

AbstractCdSe nanocrystals chemically linked to nanocrystalline titanium dioxide substrates form a promising material for nanostructured photovoltaic devices. The usual method for attaching the nanocrystals to the titanium dioxide substrate is by means of a linking molecule (such as mercaptopropionic acid) or in-situ growth. In this paper, we report the use of an alternative technique, electrophoretic deposition (EPD), to directly deposit already formed CdSe nanocrystals onto the substrate. In EPD, a voltage is established between two electrodes that are immersed in a solution of nanocrystals. At room temperature, a fraction of the nanocrystals are thermally charged, and these charged nanocrystals migrate to the electrodes and adhere to the surface. A significant advantage of EPD over the use of linking molecules is the speed with which the nanocrystals are deposited: EPD takes only a few minutes, compared to the several hours required for the alternative techniques. Additionally, we have fabricated initial photovoltaic devices based on electrophoretically deposited CdSe nanocrystals on a planar TiO2 thin film.

Size dependent absorption kinetics of sedimenting nanoparticles

2013 ◽  
Author(s):  
Manoranjan Ghosh ◽  
Karabi Ghosh ◽  
Seema Shinde ◽  
S. C. Gadkari
Keyword(s):  
Absorption Kinetics ◽  
Size Dependent ◽  
Dependent Absorption ◽  
Kinetics Of

scholarly journals Aminophosphine Reduction Mechanisms and the Synthesis of Indium Phosphide Nanomaterials

2021 ◽  
Author(s):  
◽  
Geoffry Laufersky
Keyword(s):  
Indium Phosphide ◽  
Density Functional ◽  
Large Scale ◽  
Visible Spectrum ◽  
Size Dependent ◽  
Reduction Mechanisms ◽  
Highly Sensitive ◽  
Dependent Absorption ◽  
Entire Visible Spectrum ◽  
The Impact

<p>Indium phosphide (InP) nanomaterials are attractive for countless technological applications due to their well-placed band gap energies. The quantum confinement of these semiconductors can give rise to size-dependent absorption and emission features throughout the entire visible spectrum. Therefore, InP materials can be employed as low-toxicity fluorophores that can be implemented in high value avenues such as biological probes, lighting applications, and lasing technologies. However, large scale development of these quantum dots (QDs) has been stymied by the lack of affordable and safe phosphorus precursors. Syntheses have largely been restricted to the use of dangerous chemicals such as tris(trimethylsilyl)phosphine ((TMS)₃P), which is costly and highly sensitive to oxygen and water. Recently, less-hazardous tris(dialkylamino)phosphines have been introduced to produce InP QDs on par with those utilizing (TMS)₃P. However, a poor understanding of the reaction mechanics has resulted in difficulties tuning and optimizing this method.  In this work, density functional theory (DFT) is used to identify the mechanism of this aminophosphine precursor conversion. This understanding is then implemented to design an improved InP QD synthesis, allowing for the production of high-quality materials outside of glovebox conditions. Time is spent understanding the impact of different precursor salts on the reaction mechanisms and discerning their subsequent effects on nanoparticle size and quality. The motivation of this work is to formulate safer and less technical indium phosphide quantum dot syntheses to foster non-specialist and industrial implementation of these materials.</p>

Molecular Packing-Dependent Exciton and Polariton Dynamics in Anthradithiophene Organic Crystals

MRS Advances ◽  
2018 ◽  
Vol 3 (59) ◽  
pp. 3465-3470 ◽  
Author(s):  
Jonathan D B Van Schenck ◽  
Gregory Giesbers ◽  
Akash Kannegulla ◽  
Li-Jing Cheng ◽  
John E. Anthony ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Energy Absorption ◽  
Absorption Spectra ◽  
Organic Crystals ◽  
Optical Microcavities ◽  
Enhanced Absorption ◽  
Excitonic Transition ◽  
Dependent Absorption ◽  
Derivatives Of ◽  
Primary Contribution

AbstractPolarization-dependent absorption spectra of two functionalized derivatives of fluorinated anthradithiophene, diF TES-ADT and diF TDMS-ADT, were studied in the crystal phase using a Holstein-like Hamiltonian. For both molecules, the primary contribution to the lowest energy absorption was found to be the S0-S1 excitonic transition perturbed by an intermolecular coupling of 15 meV for both TES and TDMS. A secondary contribution, consistent with that from charge-transfer states, was also found. Additionally, absorption spectra were analysed when crystals were placed inside of optical microcavities formed by two metal mirrors. Cavities exhibited a primary absorption peak determined to be an enhanced absorption from the lowest-energy S0-S1 transition.

scholarly journals Ultrafast dynamics of a bi-stable azopyridine Ni-porphyrin spin switch after photoexcitation in the porphyrin B-bands

2019 ◽  
Vol 205 ◽  
pp. 05019
Author(s):  
Sebastian Megow ◽  
Julia Bahrenburg ◽  
Mark Dittner ◽  
Birthe Kohly ◽  
Joachim Gripp ◽  
...  
Keyword(s):  
High Spin ◽  
Room Temperature ◽  
Ultrafast Dynamics ◽  
Time Resolved ◽  
Spin Switch ◽  
Absorption Measurements

Femtosecond time-resolved absorption measurements of a magnetically bi-stable azopyridine Ni-porphyrin in solution at room temperature show that the photo-induced dynamics are dominated by transient low-spin ⇄ high-spin interconversion involving Ni (d2) and (d, d) states.

scholarly journals Quantum Phenomena in Nanomaterials: Coherent Superpositions of Fine Structure States in CdSe Nanocrystals at Room Temperature

2019 ◽  
Vol 123 (51) ◽  
pp. 31286-31293 ◽  
Author(s):  
Elisabetta Collini ◽  
Hugo Gattuso ◽  
Luca Bolzonello ◽  
Andrea Casotto ◽  
Andrea Volpato ◽  
...  
Keyword(s):  
Fine Structure ◽  
Room Temperature ◽  
Cdse Nanocrystals ◽  
Quantum Phenomena

Molecular Beam Epitaxy of Znl-x Cdx Se/ZnSe Heterostructures And Their Optical Properties

1991 ◽  
Vol 228 ◽  
Author(s):  
H. Luo ◽  
N. Samarth ◽  
J. K. Furdyna ◽  
H. Jeon ◽  
J. Ding ◽  
...  
Keyword(s):  
Optical Properties ◽  
Molecular Beam Epitaxy ◽  
Quantum Wells ◽  
Room Temperature ◽  
Molecular Beam ◽  
Stimulated Emission ◽  
Optically Pumped ◽  
Absorption Coefficients ◽  
Excitonic Absorption ◽  
Lasing Mechanism

ABSTRACTSuperlattices and quantum wells of Znl-xCdxSe/ZnSe, and heterostructures based on ZnSe/CdSe digital alloys have been grown by molecular beam epitaxy (MBE). Their optical properties were studied with particular emphasis on excitonic absorption and photopumped stimulated emission. Excitonic absorption is easily observable up to 400 K, and is characterized by extremely large absorption coefficients (α = 2×105cm−1). Optically pumped lasing action is obtained at room temperature with a typical threshold intensity of 100 kW/cm2. The lasing mechanism in these II-VI quantum wells appears to be quite different from that in the better studied III-V materials: in our case, the onset of stimulated emission occurs before the saturation of the excitonic absorption, and the stimulated emission occurs at an energy lower than that of the excitonic absorption.

Sign in / Sign up

Export Citation Format

Share Document