Is Thermal and Light-Induced Annealing of Met Astable Defects in a-Si:H Driven by Electrons?

ABSTRACTWe report results of a search for a unifying rate law for the annealing of metastable defects in hydrogenated amorphous silicon (a-Si:H). We tested the hypothesis that defect-annealing by both heating or illumination is driven by the density of free electrons. This hypothesis is formulated via the rate equation - dN/dt = A nα N f (T), where N is the defect density, t the time, A a constant, n the free electron density, and f (T) a function of temperature derived from a distribution of annealing energies. The model fits two sets of data, with light-intensity and electrical conductivity as the independent variables, reasonably well, with a ranging from 0.39 to 0.76, but not the third set, where we varied the temperature.

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Comparison of Dark and Light-Induced Annealing of Metastable Defects in a-Si:H

MRS Proceedings ◽

10.1557/proc-336-245 ◽

1994 ◽

Vol 336 ◽

Cited By ~ 1

Author(s):

Helena Gleskova ◽

M. Nakata ◽

S. Wagner

Keyword(s):

Thermal Activation ◽

Defect Density ◽

Hydrogenated Amorphous Silicon ◽

Annealing Process ◽

Free Electrons ◽

Initial Value ◽

Free Electron Density ◽

Rate Law ◽

Hydrogenated Amorphous ◽

Annealing Experiments

ABSTRACTWe propose a rate law that unifies the dark and light-induced annealing of metastable defects in hydrogenated Amorphous silicon (a-Si:H). Its form is dN/dt ∼ - C Naf (T), where N is the defect density, C the concentration of free electrons (holes), f (T) a dispersive function, t the time, and T the temperature. Special dark and light-annealing experiments, designed to keep the free electron density constant, were conducted to eliminate C from the rate law. We find that f (T) for the dark annealing process differs from that for light-annealing. We calculated the thermal activation energies for the decay of N to 1/e of its initial value. They are 1.56±0.2 eV for dark annealing and 0.91±0.2 eV for light-induced annealing.

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Light-Induced Metastable Defects or Light-Induced Metastable H Atoms in a-Si:H Films?

MRS Proceedings ◽

10.1557/proc-467-79 ◽

1997 ◽

Vol 467 ◽

Author(s):

C. Godet

Keyword(s):

Experimental Data ◽

Characteristic Time ◽

Defect Density ◽

Hydrogenated Amorphous Silicon ◽

Exponential Time ◽

Mobile Species ◽

Hydrogenated Amorphous ◽

Two Parameter ◽

Metastable Defect ◽

Trapping Sites

ABSTRACTIn hydrogenated amorphous silicon (a-Si:H) films, the increase of the metastable defect density under high-intensity illumination is usually described by an empirical two-parameter stretched-exponential time dependence (characteristic time τSE and dispersion parameter β). In this study, a clearly different (one-parameter) analytic function is obtained from a microscopic model based on the formation of metastable H (MSH) atoms in a-Si:H films. Assuming that MSH atoms are the only mobile species, only three chemical reactions are significant : MSH are produced from doubly hydrogenated (SiH HSi) configurations and trapped either at broken bonds or Si-H bonds, corresponding respectively to light-induced annealing (LIA) and light-induced creation (LIC) of defects. Competition between trapping sites results in a saturation of N(t) at a steady-state value Nss. A one-parameter fit of this analytical function to experimental data is generally good, indicating that the use of a statistical distribution of trap energies is not necessary.

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Numerical Design of Ultrathin Hydrogenated Amorphous Silicon-Based Solar Cell

International Journal of Photoenergy ◽

10.1155/2021/7506837 ◽

2021 ◽

Vol 2021 ◽

pp. 1-13

Author(s):

F. X. Abomo Abega ◽

A. Teyou Ngoupo ◽

J. M. B. Ndjaka

Keyword(s):

Solar Cells ◽

Solar Cell ◽

Amorphous Silicon ◽

Buffer Layer ◽

Defect Density ◽

Hydrogenated Amorphous Silicon ◽

Theoretical Work ◽

Silicon Based ◽

The Impact ◽

Hydrogenated Amorphous

Numerical modelling is used to confirm experimental and theoretical work. The aim of this work is to present how to simulate ultrathin hydrogenated amorphous silicon- (a-Si:H-) based solar cells with a ITO BRL in their architectures. The results obtained in this study come from SCAPS-1D software. In the first step, the comparison between the J-V characteristics of simulation and experiment of the ultrathin a-Si:H-based solar cell is in agreement. Secondly, to explore the impact of certain properties of the solar cell, investigations focus on the study of the influence of the intrinsic layer and the buffer layer/absorber interface on the electrical parameters ( J SC , V OC , FF, and η ). The increase of the intrinsic layer thickness improves performance, while the bulk defect density of the intrinsic layer and the surface defect density of the buffer layer/ i -(a-Si:H) interface, respectively, in the ranges [109 cm-3, 1015 cm-3] and [1010 cm-2, 5 × 10 13 cm-2], do not affect the performance of the ultrathin a-Si:H-based solar cell. Analysis also shows that with approximately 1 μm thickness of the intrinsic layer, the optimum conversion efficiency is 12.71% ( J SC = 18.95 mA · c m − 2 , V OC = 0.973 V , and FF = 68.95 % ). This work presents a contribution to improving the performance of a-Si-based solar cells.

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Reduction of the Defect Density in a-Si:H Deposited at ≤250°C

MRS Proceedings ◽

10.1557/proc-297-91 ◽

1993 ◽

Vol 297 ◽

Cited By ~ 4

Author(s):

Hitoshi Nishio ◽

Gautam Ganguly ◽

Akihisa Matsuda

Keyword(s):

Diffusion Coefficient ◽

Amorphous Silicon ◽

Surface Diffusion ◽

Film Growth ◽

Defect Density ◽

Hydrogenated Amorphous Silicon ◽

Device Fabrication ◽

Surface Diffusion Coefficient ◽

Hydrogenated Amorphous ◽

Substrate Temperatures

We present a method to reduce the defect density in hydrogenated amorphous silicon (a-Si:H) deposited at low substrate temperatures similar to those used for device fabrication . Film-growth precursors are energized by a heated mesh to enhance their surface diffusion coefficient and this enables them to saturate more surface dangling bonds.

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Improved Light Soaking Stability of R.F. Sputter Deposited Amorphous Silicon

MRS Proceedings ◽

10.1557/proc-219-105 ◽

1991 ◽

Vol 219 ◽

Author(s):

A. Wynveen ◽

J. Fan ◽

J. Kakalios ◽

J. Shinar

Keyword(s):

Amorphous Silicon ◽

Hydrogen Content ◽

Defect Density ◽

Hydrogenated Amorphous Silicon ◽

Dark Conductivity ◽

Initial Defect ◽

Optical Gap ◽

Sputter Deposited ◽

Staebler Wronski Effect ◽

Hydrogenated Amorphous

ABSTRACTStudies of r.f. sputter deposited hydrogenated amorphous silicon (a-Si:H) find that the light induced decrease in the dark conductivity and photoconductivity (the Staebler-Wronski effect) is reduced when the r.f. power used during deposition is increased. The slower Staebler-Wronski effect is not due to an increase in the initial defect density in the high r.f. power samples, but may result from either the lower hydrogen content or the smaller optical gap found in these films.

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Electron trapping and paramagnetic defect density measurements in hydrogenated amorphous silicon

Solar Cells ◽

10.1016/0379-6787(89)90044-6 ◽

1989 ◽

Vol 27 (1-4) ◽

pp. 357-362 ◽

Cited By ~ 10

Author(s):

S.P. Hotaling ◽

Homer Antoniadis ◽

E.A. Schiff

Keyword(s):

Amorphous Silicon ◽

Defect Density ◽

Hydrogenated Amorphous Silicon ◽

Electron Trapping ◽

Paramagnetic Defect ◽

Density Measurements ◽

Hydrogenated Amorphous

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Effects of Intermittent Deposition on the Defect Density in a-Si:H

MRS Proceedings ◽

10.1557/proc-336-31 ◽

1994 ◽

Vol 336 ◽

Author(s):

Toshihiro Kamei ◽

Nobuhiro Hata ◽

Akihisa Matsuda

Keyword(s):

Waiting Time ◽

Defect Density ◽

Hydrogenated Amorphous Silicon ◽

Hydrogen Desorption ◽

Growth Surface ◽

Dangling Bond ◽

Monolayer Growth ◽

Hydrogenated Amorphous ◽

Substrate Temperatures ◽

Mechanical Shutter

ABSTRACTEffects of intermittent deposition on the defect density in hydrogenated Amorphous silicon (a-Si:H) are investigated at various substrate temperatures by using a mechanical shutter, while maintaining the discharge continuously. The intermittent deposition experiments, where monolayer growth and intermission (waiting time) are repeated in cycles, enable us to study surface dangling bond (DB) recombination and thermal hydrogen desorption separately from other reactions on the growth surface. The defect density in films prepared at lower substrate temperatures decreases with the waiting time, while that deposited at higher substrate temperatures increases with the waiting time.

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Saturation behavior of the light-induced defect density in hydrogenated amorphous silicon (solar cells)

10.1109/pvsc.1990.111887 ◽

2002 ◽

Author(s):

H.R. Park ◽

J.Z. Liu ◽

P. Roca i Cabarrocas ◽

A. Maruyama ◽

M. Isomura ◽

...

Keyword(s):

Solar Cells ◽

Amorphous Silicon ◽

Defect Density ◽

Hydrogenated Amorphous Silicon ◽

Silicon Solar Cells ◽

Hydrogenated Amorphous

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Effect of Deposition-Induced Annealable Defects on Light-Induced Defect Generation in a-Si:H

MRS Proceedings ◽

10.1557/proc-297-565 ◽

1993 ◽

Vol 297 ◽

Author(s):

Jong-Hwan Yoon

Keyword(s):

Amorphous Silicon ◽

Defect Density ◽

Hydrogenated Amorphous Silicon ◽

Generation Rate ◽

Defect Generation ◽

Saturated State ◽

Microscopic Models ◽

Hydrogenated Amorphous ◽

Substrate Temperatures

In this paper we present a method to determine the annealable defect density(ΔNann) present in hydrogenated amorphous silicon(a-Si:H). The effects of the annealable defects on the light-induced defect generation rate, saturated defect density (Nsat) and the change of defect density in the light-induced saturated state(ΔNsat) have been studied. Annealable defect density was varied by depositing samples at various substrate temperatures or by post-growth anneals of samples grown at low substrate temperatures. It is found that the generation rate, N satand ΔNsat are well correlated with ΔNann. In particular, the ΔNsat is found to follow a relation ΔNsat ≈ ΔNann. These results suggest that defect-related microscopic models are appropriate for light-induced metastability.

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The Concentration of (SiH2)n Sites in Low and High Defect Density a-Si:H

MRS Proceedings ◽

10.1557/proc-0910-a09-04 ◽

2006 ◽

Vol 910 ◽

Author(s):

David C. Bobela ◽

T. Su ◽

P. C. Taylor ◽

A. Madan ◽

G. Ganguly

Keyword(s):

Nuclear Magnetic Resonance ◽

Magnetic Resonance ◽

Hydrogen Content ◽

Defect Density ◽

Hydrogenated Amorphous Silicon ◽

Proton Nuclear Magnetic Resonance ◽

Dangling Bond ◽

High Defect Density ◽

Quality Material ◽

Hydrogenated Amorphous

AbstractThe concentration of polysilane chains (SiH2)n, where n≥1, is estimated for higher quality hydrogenated amorphous silicon (a-Si:H) by pulsed proton nuclear magnetic resonance techniques (1H NMR). Our measurements indicate the minimum hydrogen content of approximately 10% of the total hydrogen is in the (SiH2)n configuration. Similar measurements in a high defect density sample (1017 silicon dangling bond defects cm-3) show that (SiH2)n sites account for ~ 15% of the total hydrogen. While the (SiH2)n infrared absorption (IR) modes are observed in the highly defective sample, no such modes are seen in the higher quality material. The results indicate that a significant amount of the total hydrogen content exists as (SiH2)n regardless of film quality.

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