scholarly journals Carrier density and compensation in semiconductors with multi dopants and multi transition energy levels: The case of Cu impurity in CdTe

2011 ◽  
Author(s):  
Su-Huai Wei ◽  
Jie Ma ◽  
T. A. Gessert ◽  
Ken K. Chin
Keyword(s):  
Carrier Density ◽  
Transition Energy ◽  
Energy Levels

The 0.9 eV Absorption Band of Polyaniline: A Morphologically Sensitive Electronic Absorption

1989 ◽  
Vol 173 ◽  
Author(s):  
D. Zhang ◽  
J.-H. Hwang ◽  
S. C. Yang
Keyword(s):  
Absorption Band ◽  
Electronic Absorption ◽  
Transition Energy ◽  
Energy Levels ◽  
Electronic Energy ◽  
Emeraldine Base ◽  
Electronic Systems ◽  
Electrically Conductive ◽  
Electronic Energy Levels ◽  
Electronic Absorption Band

The optical absorption spectra of polyaniline in the visible and UV spectral regions have been characterized before. The electrically conductive form has a band gap absorption at 3.8 eV and polaron absorptions at 2.9 and 1.5 eV [1,2] . An additional electronic absorption band at 0.9 eV was found to be also related to the existence of polaron. The assignment of this transition has yet to be made. Epstein and co-workers [31 have found a photo-induced absorption band at 0.9 eV by photo-exciting emeraldine base (insulator) with 2.0 eV light. It is not known yet whether these two 0.9 eV transitions belong to the same set of electronic energy levels of polaron, or they belong to two different electronic systems but are coincidentally have the same transition energy.

Study on Organic Triplet Exciton Emission and Quenching Processes by Low-temperature Photo- and Electroluminescence Spectroscopy

2008 ◽  
Vol 1115 ◽  
Author(s):  
Nils Asmus Kristian Kaufmann ◽  
Frank Jessen ◽  
M. Heuken ◽  
Herbert Boerner ◽  
Holger Kalisch ◽  
...  
Keyword(s):  
Low Temperature ◽  
Charge Carrier ◽  
Carrier Density ◽  
Organic Materials ◽  
Energy Levels ◽  
Triplet Exciton ◽  
Light Sources ◽  
Charge Carrier Density ◽  
Electrical Excitation

AbstractOrganic light emitting diodes (OLED) are efficient light sources based on organic semiconductors. Unlike inorganic LEDs which are more or less point sources, OLED are planar light sources with up to 1 m2 in area. By using organic materials, they are cheap to produce and economical to use. The determination of triplet exciton energy levels is of interest for the development of efficient OLED, based on the fact that electrical excitation usually creates three times as many triplets as singlets. Additionally, the knowledge of these energy levels is crucial for the design and choice of emitter matrix materials and exciton blocking layers. These values are normally determined by photoluminescence (PL) measurements in solution for materials which show intersystem crossing (ISC) between singlet and triplet states. For some materials, the triplet levels cannot be measured this way because some materials prohibit ISC. In this work, a method is presented which allows the determination of the energy levels using low-temperature electroluminescence (EL) spectroscopy. The dependence on ISC is avoided by creating triplets directly with electrical excitation and this allows to measure a large class of organic materials. A low-temperature EL spectrum is presented for N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine (TPD) in a 3-phenyl-4-(1‘-naphthyl)-5-phenyl-1,2,4-triazole (TAZ) matrix (TPD/TAZ 1:3) at 77 K. Triplet emission is only observed at very low charge carrier density (0.5 μA/mm2). Quenching processes are analyzed using combined EL and PL measurements and unipolar devices. Two factors can be the cause of the quenching: A strong quenching based on a low concentration of electrically activated impurities could explain the dependency. The other explanation points to a quenching based on electrons in the emitting layer. This might be explained with triplet-polaron quenching (TPQ). TPQ is proportional to the charge carrier density and contributes the dominant part to the quenching at low current densities.

ENERGY LEVELS OF A POLARON IN A FINITE PARABOLIC QUANTUM WELL

2001 ◽  
Vol 15 (05) ◽  
pp. 527-535 ◽  
Author(s):  
FENG-QI ZHAO ◽  
XI XIA LIANG ◽  
SHILIANG BAN
Keyword(s):  
Excited State ◽  
Variational Method ◽  
Quantum Well ◽  
Ground State ◽  
Transition Energy ◽  
Energy Levels ◽  
Phonon Interaction ◽  
Electron Phonon Interaction ◽  
Hole Energy ◽  
First Excited State

The effects of the electron–phonon interaction on the electron (or hole) energy levels in parabolic quantum well (PQW) structures are studied. The ground state, the first excited state and the transition energy of the electron (or hole) in the GaAs/Al 0.3 Ga 0.7 As parabolic quantum well are calculated by using a modified Lee–Low–Pines Variational method. The numerical results are given and discussed. A comparison between the theoretical and experimental results is made.

BINDING ENERGY OF A BOUND POLARON IN THE FINITE PARABOLIC QUANTUM WELL

2001 ◽  
Vol 15 (20) ◽  
pp. 827-835 ◽  
Author(s):  
FENG-QI ZHAO ◽  
XI XIA LIANG
Keyword(s):  
Binding Energy ◽  
Quantum Well ◽  
Ground State Energy ◽  
Ground State ◽  
State Energy ◽  
Transition Energy ◽  
Energy Levels ◽  
Phonon Interaction ◽  
Electron Phonon Interaction ◽  
Bound Polaron

We have studied the effect of the electron–phonon interaction on the energy levels of the bound polaron and calculated the ground-state energy, the binding energy of the ground state, and the 1 s → 2 p ± transition energy in the GaAs/Al x Ga 1-x As parabolic quantum well (PQW) structure by using a modified Lee–Low–Pines (LLP) variational method. The numerical results are given and discussed. It is found that the contribution of electron–phonon interaction to the ground-state energy and the binding energy is obvious, especially in large well-width PQWs. The electron–phonon interaction should not be neglected.

scholarly journals Trap‐Assisted Transition Energy Levels of SrF 2 :Pr 3+ −Yb 3+ Nanophosphor in TiO 2 Photoanode for Luminescence Tuning in Dye‐Sensitized Photovoltaic Cells

Solar RRL ◽  
2021 ◽  
Vol 5 (10) ◽  
pp. 2170101
Author(s):  
Ashok Kumar Kaliamurthy ◽  
Hyeong Cheol Kang ◽  
Francis Kwaku Asiam ◽  
Kicheon Yoo ◽  
Jae-Joon Lee
Keyword(s):  
Transition Energy ◽  
Energy Levels ◽  
Photovoltaic Cells ◽  
Dye Sensitized

Polaronic Effects in Wurtzite InxGa1-xN/GaN Parabolic Quantum Well

2012 ◽  
Vol 629 ◽  
pp. 145-151
Author(s):  
Ren Tu Ya Wu ◽  
Qi Zhao Feng
Keyword(s):  
Quantum Well ◽  
Ground State Energy ◽  
Optical Phonon ◽  
Ground State ◽  
State Energy ◽  
Transition Energy ◽  
Energy Levels ◽  
Phonon Modes ◽  
Phonon Interaction ◽  
Zinc Blende

The energy levels of polaron in a wurtzite InxGa1-xN/GaN parabolic quantum well are investigated by adopting a modified Lee-Low-Pines variational method. The ground state energy, the transition energy and the contributions of different branches of optical phonon modes to the ground state energy as functions of the well width are given. The effects of the anisotropy of optical phonon modes and the spatial dependence effective mass, dielectric constant, phonon frequency on energy levels are considered in calculation. In order to compare, the corresponding results in zinc-blende parabolic quantum well are given. The results indicate that the contributions of the electron-optical phonon interaction to ground state energy of polaron in InxGa1-xN/GaN is very large, and make the energy of polaron reduces. For a narrower quantum well，the contributions of half-space optical phonon modes is large , while for a wider one, the contributions of the confined optical phonon modes are larger. The ground state energy and the transition energy of polaron in wurtzite InxGa1-xN/GaN are smaller than that of zinc-blende InxGa1-xN/GaN, and the contributions of the electron-optical phonon interaction to ground state energy of polaron in wurtzite InxGa1-xN/GaN are greater than that of zinc-blende InxGa1-xN/GaN. The contributions of the electron-optical phonon interaction to ground state energy of polaron in wurtzite InxGa1-xN/GaN (about from 22 to 32 meV) are greater than that of GaAs/AlxGa1-xAs parabolic quantum well (about from 1.8 to 3.2 meV). Therefore, the electron-optical phonon interaction should be considered for studying electron state in InxGa1-xN/GaN parabolic quantum well.

Effects of Segregation on the Strain Fields and Electronic Structures of InAs Quantum Dots

2009 ◽  
Author(s):  
Kuo-Bin Hong ◽  
Mao-Kuen Kuo
Keyword(s):  
Quantum Dots ◽  
Electronic Structures ◽  
Transition Energy ◽  
Energy Levels ◽  
Energy Difference ◽  
Strain Component ◽  
Strain Fields ◽  
Inas Quantum Dots ◽  
Mismatch Strain ◽  
Two Samples

This paper investigates the influence of indium segregation on the strain fields and electronic structures of self-assembled InAs/GaAs quantum dot structures with and without an In0.15Ga0.85As interlayer. We propose a new out-of-plane mismatch strain to interpret an experimental phenomenon. The new mismatch strain simulation successfully analyzes the strain fields and energy levels of InAs quantum dots (QDs). Numerical results reveal that indium segregation would improve the penetration behaviour of the z-axis strain component and the relaxation of the hydrostatic strain. The transition energy of samples A and B without In segregation are 0.991 and 1.028 eV, respectively. The energy difference of two samples agrees well with the previous experimental results. The transition energy of samples A and B may be consistent with presented experiment data at R = 0.84–0.85. In our calculations, indium segregation not only made the transition energy increase significantly as segregation efficiency increased, but also the confinement position of the electron and the heavy-hole shifted toward the top of the QD. Similar phenomena can also be observed for other segregation efficiencies.

Control of Doping and Electronic Transport in Nanowires

2004 ◽  
Vol 820 ◽  
Author(s):  
Jianxin Zhong ◽  
G. Malcolm Stocks
Keyword(s):  
Energy Level ◽  
Fermi Energy ◽  
Disordered Systems ◽  
Carrier Mobility ◽  
Transition Energy ◽  
Energy Levels ◽  
Three Dimensional ◽  
Delta Doping ◽  
Surface Disorder ◽  
Novel Concept

AbstractWe propose a novel concept, namely, delta-doping of nanowires, to control the carrier mobility in nanowires. Different from the traditional doping, our approach features doping of a nanowire only on its surface. Our calculations based on Anderson models for nanowires with surface disorder showed remarkably different results from the traditional doping where impurities are distributed inside the nanowire. We found that there exist transition energy levels similar to the mobility edges in three-dimensional disordered systems. If the Fermi energy is below the transition energy level, the delta-doped nanowire is simply an insulator. But once the Fermi energy exceeds this energy level, the carrier mobility increases significantly. The transition levels are almost independent of the degree of disorder in the regime of strong disorder.

Trap Assisted Transition Energy Levels of SrF2:Pr3+-Yb3+ Nanophosphor in TiO2 Photoanode for Luminescence Tuning in Dye-Sensitized Photovoltaic Cells

2021 ◽  
Vol MA2021-02 (13) ◽  
pp. 646-646
Author(s):  
Ashok Kumar Kaliamurthy ◽  
Hyeong Cheol Kang ◽  
Francis Kwaku Asiam ◽  
Kicheon Yoo ◽  
Jae-Joon Lee
Keyword(s):  
Transition Energy ◽  
Energy Levels ◽  
Photovoltaic Cells ◽  
Dye Sensitized ◽  
Tio2 Photoanode
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