Recombination of Excess Carriers at High Excitation Density in Amorphous Silicon

1993 ◽  
Vol 297 ◽  
Author(s):  
M. Kunst ◽  
C. Haffer ◽  
C. Swiatkowski
Keyword(s):  
Experimental Data ◽  
Amorphous Silicon ◽  
Numerical Models ◽  
Time Range ◽  
Excitation Density ◽  
High Excitation ◽  
Electron Hole ◽  
Transient Photoconductivity ◽  
Boron Doped ◽  
Hole Recombination

Excess electron-hole recombination at high excitation densities in a-Si:H is investigated by comparison of the transient photoconductivity during and just after excitation in the nanosecond time range to numerical models. A simple one parameter recombination model fits the experimental data satisfactorily. An extension of the model where deep trapping is taken into account explains also the transient photoconductivity in Boron doped a-Si:H.

Transient Photoconductivity in GaAs Films Grown by Molecular Beam Epitaxy.

1989 ◽  
Vol 145 ◽  
Author(s):  
A. Werner ◽  
T. D. Moustakas ◽  
M. Kunst
Keyword(s):  
Fast Decay ◽  
Electron Hole ◽  
Effective Electron ◽  
Decay Channels ◽  
Decay Component ◽  
Transient Photoconductivity ◽  
High Impurity ◽  
Gaas Films ◽  
Silicon Doped ◽  
Hole Recombination

AbstractHahn-Meitner-Institut, D-1000 Berlin 39, W. Germany Abstract The transient photoconductivity, in MBE grown silicon doped GaAs films, was studied by a contactless microwave conductivity technique. The dark carrier concentration of the investigated films varies from 4 x 1014 cm-3 to 6 x 1017 cm-3. At least two decay channels can be distinguished. An initial fast decay process (t<20 ns), which is excitation intensity dependent, followed by a slower one. The fast decay is tentativly identified with a direct electron-hole recombination and is more pronounced at high excitation intensities and in low impurity materials. The slower decay component is characterized by effective electron lifetimes ranging from 2 µs for low impurity fims up to 100 µs for high impurity samples. It can be concluded that an increase of the Si-concentration leads to an increase in the concentration of hole traps, which quenches the initial electron-hole recombination and decreases the electron decay rate in the microsecond region.

Improvement of Single-Junction a-Si:H Thin-Film Solar Cells Toward 10% Efficiency

2011 ◽  
Vol 1321 ◽  
Author(s):  
P. H. Cheng ◽  
S. W. Liang ◽  
Y. P. Lin ◽  
H. J. Hsu ◽  
C. H. Hsu ◽  
...  
Keyword(s):  
Thin Film ◽  
Solar Cells ◽  
Amorphous Silicon ◽  
Chemical Vapor ◽  
Thin Film Solar Cells ◽  
Window Layer ◽  
Electron Hole ◽  
Single Junction ◽  
Boron Doped ◽  
Hydrogenated Amorphous

ABSTRACTThe hydrogenated amorphous silicon (a-Si:H) single-junction thin-film solar cells were fabricated on SnO2:F-coated glasses by plasma-enhanced chemical vapor deposition (PECVD) system. The boron-doped amorphous silicon carbide (a-SiC:H) was served as the window layer (p-layer) and the undoped a-SiC:H was used as a buffer layer (b-layer). The optimization of the p/b/i/n thin-films in a-Si:H solar cells have been carried out and discussed. Considering the effects of light absorption, electron-hole extraction and light-induced degradation, the thicknesses of p, b, n and i layers have been optimized. The optimal a-Si:H thin-film solar cell having an efficiency of 9.46% was achieved, with VOC=906 mV, JSC=14.42 mA/cm2 and FF=72.36%.

Electron‐hole recombination in reactively sputtered amorphous silicon solar cells

1981 ◽  
Vol 39 (9) ◽  
pp. 721-723 ◽  
Author(s):  
T. D. Moustakas ◽  
C. R. Wronski ◽  
T. Tiedje
Keyword(s):  
Solar Cells ◽  
Amorphous Silicon ◽  
Silicon Solar Cells ◽  
Electron Hole ◽  
Hole Recombination

Optical-Gain Measurements on GaN and Alx Ga1-xN Heterostructures

1997 ◽  
Vol 468 ◽  
Author(s):  
L. Eckey ◽  
J. Holst ◽  
V. Kutzer ◽  
A. Hoffmann ◽  
I. Broser ◽  
...  
Keyword(s):  
High Temperatures ◽  
Low Temperatures ◽  
Optical Gain ◽  
Excitation Density ◽  
High Excitation ◽  
Electron Hole ◽  
Hole Plasma ◽  
Electron Hole Plasma ◽  
Stripe Length ◽  
Density Results

ABSTRACTOptical gain processes in thin GaN and AlGaN are compared by means of gain spectroscopy using the stripe length method and high-excitation photoluminescence, both performed at various densities and temperatures. We find that inelastic excitonic scattering processes and biexciton decay are important at low temperatures and low excitation densities Both materials are similar in that increasing the excitation density results in gain spectra dominated by the electron-hole plasma and phonon-assisted band-to-band recombination. These also prevail at high temperatures.

Numerical Simulation of the Transient Photoconductivity in A-SI:H as a Function of the Excitation Density

1997 ◽  
Vol 467 ◽  
Author(s):  
H. Feist ◽  
M. Kunst
Keyword(s):  
Density Dependence ◽  
Conduction Band ◽  
Dynamic Equilibrium ◽  
Localized States ◽  
Time Range ◽  
Excitation Density ◽  
Band Tail ◽  
Transient Photoconductivity ◽  
Excess Electrons ◽  
Short Time

ABSTRACTThe dependence of the transient photoconductivity induced by pulsed excitation (TPC) on the excitation density is discussed with the help of numerical simulations. It is shown that recombination between excess mobile electrons and all excess holes (mainly localized) can explain the excitation density dependence of the TPC amplitude of standard a-Si:H at room temperature using a rate parameter kBB of 10−8cm3/s. This model leads to a decay faster than experimentally observed in the time range from 40ns to 1 μs. A variation of the recombination model is presented that gives a better fit for the longer time range still showing the correct excitation density dependence in the short time range. Moreover comparison of the simulations with experimental data yields limits for the parameters of the conduction band tail. In particular, the time necessary to establish a dynamic equilibrium of excess electrons between delocalized states in the conduction band and localized states in the tail appears to be very informative.

Optically Detected Magnetic Resonance and Double Beam Photoluminescence of CdS/HgS/CdS Nanoparticles

1998 ◽  
Vol 536 ◽  
Author(s):  
H. Porteanu ◽  
A. Glozman ◽  
E. Lifshitz ◽  
A. Eychmüller ◽  
H. Weller
Keyword(s):  
Optical Properties ◽  
Magnetic Resonance ◽  
Cds Nanoparticles ◽  
Electron Hole ◽  
Cladding Layer ◽  
Double Beam ◽  
Optically Detected Magnetic Resonance ◽  
Optically Detected ◽  
Cladding Layers ◽  
Hole Recombination

AbstractCdS/HgS/CdS nanoparticles consist of a CdS core, epitaxially covered by one or two monolayers of HgS and additional cladding layers of CdS. The present paper describes our efforts to identify the influence of CdS/HgS/CdS interfaces on the localization of the photogenerated carriers deduced from the magneto-optical properties of the materials. These were investigated by the utilization of optically detected magnetic resonance (ODMR) and double-beam photoluminescence spectroscopy. A photoluminescence (PL) spectrum of the studied material, consists of a dominant exciton located at the HgS layer, and additional non-excitonic band, presumably corresponding to the recombination of trapped carriers at the interface. The latter band can be attenuated using an additional red excitation. The ODMR measurements show the existence of two kinds of electron-hole recombination. These electron-hole pairs maybe trapped either at a twin packing of a CdS/HgS interface, or at an edge dislocation of an epitaxial HgS or a CdS cladding layer.

Identifying Physico-Chemical Laws from the Robotically Collected Data

2019 ◽  
Author(s):  
Liwei Cao ◽  
Danilo Russo ◽  
Vassilios S. Vassiliadis ◽  
Alexei Lapkin
Keyword(s):  
Experimental Data ◽  
Numerical Models ◽  
Predictor Variable ◽  
Physical Models ◽  
Training Data ◽  
Mixed Integer ◽  
Physico Chemical ◽  
Data Points ◽  
Future Work ◽  
The Relationship

<p>A mixed-integer nonlinear programming (MINLP) formulation for symbolic regression was proposed to identify physical models from noisy experimental data. The formulation was tested using numerical models and was found to be more efficient than the previous literature example with respect to the number of predictor variables and training data points. The globally optimal search was extended to identify physical models and to cope with noise in the experimental data predictor variable. The methodology was coupled with the collection of experimental data in an automated fashion, and was proven to be successful in identifying the correct physical models describing the relationship between the shear stress and shear rate for both Newtonian and non-Newtonian fluids, and simple kinetic laws of reactions. Future work will focus on addressing the limitations of the formulation presented in this work, by extending it to be able to address larger complex physical models.</p><p><br></p>

Pre-Industrial Experience in Solar Photocatalytic Mineralization of Real Wastewaters. Application to Pesticide Container Recycling

1999 ◽  
Vol 40 (4-5) ◽  
pp. 123-130 ◽  
Author(s):  
S. Malato ◽  
J. Blanco ◽  
C. Richter ◽  
B. Milow ◽  
M. I. Maldonado
Keyword(s):  
Organic Contaminants ◽  
Toxic Waste ◽  
Experimental Plant ◽  
Electron Hole ◽  
Particulate Suspensions ◽  
Photocatalytic System ◽  
Commercial Pesticide ◽  
Pesticide Container ◽  
By Products ◽  
Hole Recombination

Particulate suspensions of TiO2 irradiated with natural solar tight in a large experimental plant catalyse the oxidation of organic contaminants. The problem in using TiO2 as a photocatalyst is electron/hole recombination. One strategy for inhibiting e−/h+ recombination is to add other (irreversible) electron acceptors to the reaction. In many highly toxic waste waters where degradation of organic pollutants is the major concern, the addition of an inorganic anion to enhance the organic degradation rate may be justified. For better results, these additives should fulfil the following criteria: dissociate into harmless by-products and lead to the formation of ·OH or other oxidising agents. In this paper, we attempt to demonstrate the optimum conditions for the treatment of commercial pesticide rinsates found in the wastewater produced by a pesticide container recycling plant. The experiments were performed in one of the pilot plants of the largest solar photocatalytic system in Europe, the Detoxification Plants of the Plataforma Solar de Almería (PSA), in Spain. After testing ten different commercial pesticides, results show that peroxydisulphate enhances the photocatalytic miniralization of all of them. This study is part of an extensive project focused on the design of a solar photocatalytic plant for decontamination of agricultural rinsates in Almería (Spain).

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