Mechanism of Enhanced Hydrogen Diffusion in Solar Cell Silicon

1992 ◽  
Vol 262 ◽  
Author(s):  
Bhushan L. Sopori
Keyword(s):  
Solar Cell ◽  
Grain Boundaries ◽  
Polycrystalline Silicon ◽  
Hydrogen Diffusion ◽  
Silicon Substrates ◽  
Hydrogen Diffusivity ◽  
Float Zone ◽  
Low Energies ◽  
High Concentrations ◽  
Mobile Vacancy

ABSTRACTExperimental results that support our previously reported observations of enhanced diffusivity of hydrogen in some solar cell silicon are presented. The diffusivities of hydrogen, implanted at low energies, were measured for several commercial silicon substrates. It is shown that the diffusivity of hydrogen in some solar cell substrates is about two orders of magnitude higher than that in Float Zone silicon in a temperature range of 100° - 300°C. This value of diffusivity is also close to that observed along some grain boundaries in polycrystalline silicon. It is determined that hydrogen in-diffusion is accompanied by an out-diffusion of boron, and that the hydrogen diffusivity is retarded by high concentrations of oxygen. A mechanism for enhanced hydrogen diffusion is proposed which invokes formation of a highly mobile vacancy-hydrogen complex.

Hydrogen Diffusivity and Solubility in Internally Oxidized Pd0.97Zr0.03 and Pd0.97Nb0.03 Alloys

2010 ◽  
Vol 297-301 ◽  
pp. 715-721
Author(s):  
E.R. Lagreca ◽  
Viviane M. Azambuja ◽  
Dílson S. dos Santos
Keyword(s):  
Diffusion Coefficient ◽  
Grain Boundaries ◽  
Hydrogen Pressure ◽  
Hydrogen Diffusion ◽  
Gas Permeation ◽  
Hydrogen Diffusivity ◽  
Sem Images ◽  
Conventional Furnace ◽  
Hydrogen Diffusion Coefficient ◽  
Preferential Segregation

Internally oxidized (I.O.) Pd0.97Zr0.03 and Pd0.97Nb0.03 alloys were submitted to gas permeation tests with temperatures in the range of 473-873 K. The internal oxidation was kept in a conventional furnace at 1073 K for 24 hours in air contact. The formation of nano-oxides, ZrO2 and Nb2O5, dispersed in the Pd matrix was observed. SEM images showed a preferential segregation of these oxides in the grain boundaries. It was observed that the diffusion coefficient in the sample containing Nb oxide was smaller than that in the Pd-Zr oxide. The effect of hydrogen pressure was investigated in the Pd-Nb samples. It was observed that the hydrogen diffusion coefficient increases with increasing the pressure. The hydrogen solubility is bigger for the Pd-Zr internally oxidized. This effect is attributed to the Zr nanoxides, which are smaller than Pd-Nb precipitates and then offer more interface for trapping the hydrogen.

Investigation of Hydrogen Diffusion Characteristics of the Heat Affected Zone of 2.25Cr-1Mo-0.25V Steel by an Electrochemical Permeation Method

2019 ◽  
Author(s):  
Xin Song ◽  
Zelin Han ◽  
Bin Liu ◽  
Mu Qin ◽  
Yuancai Duo ◽  
...  
Keyword(s):  
Grain Boundaries ◽  
Hydrogen Concentration ◽  
Heat Affected Zone ◽  
Hydrogen Diffusion ◽  
Trap Density ◽  
Hydrogen Diffusivity ◽  
Hydrogen Flux ◽  
Hydrogen Trap ◽  
Diffusion Characteristics ◽  
Effective Hydrogen

Abstract The heat affected zone (HAZ) of 2.25Cr-1Mo-0.25V welded joint is a critical part for the safety of hydrogenation reactors. Hydrogen has a significant effect on the HAZ, studying hydrogen diffusion characteristics, such as: hydrogen flux and the effective hydrogen diffusivity has a remarkable value in investigating the hydrogen-induced material degradation mechanisms. In this work, an electrochemical permeation method was applied to study the hydrogen diffusion characteristics of HAZ. Then, the metallographic microscope and a software “Image J” were used to analyze the density of grain boundaries of HAZ. The effect of the post–weld heat treatment (PWHT, i.e. annealing) on the hydrogen diffusion characteristics of HAZ was also been investigated. The results show that after PWHT, the effective hydrogen diffusivity of HAZ increases from 1.63 × 10−7cm2·s−1 to 3.68 × 10−7cm2·s−1, the hydrogen concentration decreases from 1.92 × 10−4mol·cm−3 to 1.09 × 10−4mol·cm−3, and the hydrogen trap density decreases from 3.00 × 1026m−3 to 0.76 × 1026m−3. Thus, PWHT can significantly reduce density of grain boundaries, thereby reducing the hydrogen trap density, enhancing the hydrogen diffusivity and reducing the hydrogen concentration.

Hydrogen Diffusion in Chalcopyrite Solar Cell Materials

1998 ◽  
Vol 513 ◽  
Author(s):  
A. Weidinger ◽  
J. Krauser ◽  
Th. Riedle ◽  
R. Klenk ◽  
M. Ch. Lux-Steiner ◽  
...  
Keyword(s):  
Thin Films ◽  
Solar Cell ◽  
Grain Boundaries ◽  
Single Crystals ◽  
Diffusion Coefficients ◽  
Transport Process ◽  
Hydrogen Diffusion ◽  
Intrinsic Diffusion ◽  
Ion Energy ◽  
Temperature Range

ABSTRACTHydrogen diffusion in CuInSe 2 single crystals and CuInS2 thin films was studied by measuring the spreading of implantation profiles upon annealing. Deep implantation with an ion energy of 10 keV and sub-surface implantation with 300 eV were applied. The diffusion coefficients in both materials were found to be in the order of 10-14 to 10-13 cm2/s in the temperature range between 400 and 520 K.These fairly low diffusivities are typical for a trap and release transport process rather than intrinsic diffusion of interstitial hydrogen. In the polycrystalline CuInS2 films, hydrogen leaves the sample through the grain boundaries.

Dolts of Polysilicon for Solar Cell Applications

1986 ◽  
Vol 71 ◽  
Author(s):  
P.K. Mclarty ◽  
Y.I. Huang ◽  
D. E. Ioannou ◽  
S.M. Johnson
Keyword(s):  
Solar Cell ◽  
Grain Boundaries ◽  
Doping Level ◽  
Polycrystalline Silicon ◽  
Schottky Diodes ◽  
Casting Technique ◽  
P Type ◽  
Electron And Hole Traps ◽  
Dlts Spectra

AbstractDLTS was applied to p—type polycrystalline silicon, grown by a casting technique to form ingots with a nominal doping level of ∼1016 acceptors/cmg. Both Schottky diodes and n+p mesa structures were used for the measurements. Very complex DLTS spectra were obtained from diodes that contained electrically active grain boundaries, whereas no traps were detected in areas that did not contain electrically active grain boundaries. Several electron and hole traps were resolved.

Measurements of Grain Boundary Trap Density and Hydrogen Diffusivity in Polycrystalline Silicon Fet's

1990 ◽  
Vol 182 ◽  
Author(s):  
Chad B. Moore ◽  
Dieter G. Ast
Keyword(s):  
Grain Boundary ◽  
Polycrystalline Silicon ◽  
Hydrogen Diffusion ◽  
State Density ◽  
Trap Density ◽  
Hydrogen Diffusivity ◽  
Trap State ◽  
Polycrystalline Silicon Films ◽  
Hydrogenation Time ◽  
Deposited Films

AbstractHydrogen diffusion in as-deposited and in oxidation-annealed polycrystalline silicon films was investigated using n-type accumulation-mode MOSFET's. The diffusion was studied by measuring the reduction in the grain boundary trap density with hydrogenation time. The number of traps in fully hydrogenated as-deposited films fell to about 45% of the initial trap state density and fell to about 20% in the oxidized-annealed films. Concurrently, the mobility increased about 95 % to 5cm2/Vs in the as-deposited films and by about 55 % to 25 cm2/Vs in the oxidized polysilicon devices. The effective preexponential diffusion coefficient and activation energy for hydrogen diffusion in the two different films were Do= 5.4×10−10 cm2/s and EA= 0.37 eV for the as-deposited polysilicon and Do=2.1×10−10 cm2/s and EA= 0.36 eV for the oxidized polysilicon.

Defect Studies in Solar Cell Silicon

1982 ◽  
Vol 40 ◽  
pp. 434-437
Author(s):  
B. Cunningham
Keyword(s):  
Solar Cells ◽  
Solar Cell ◽  
Low Cost ◽  
Structural Defects ◽  
Silicon Solar Cells ◽  
Silicon Substrates ◽  
Float Zone ◽  
Chemical Impurities ◽  
Heat Shields ◽  
Growth Methods

IntroductionOne of the requirements for low-cost silicon solar cells is that the silicon substrates be relatively inexpensive (compared to standard Czochralski and float-zone wafers). This requirement has led to the development of a number of techniques for growing silicon ‘ribbons’, e.g. edge defined film-fed growth (EFG), silicon-on-ceramic (SOC), ribbon-to-ribbon (RTR) and dendritic web. Details of these and other growth techniques can be found in ref. Most of the growth methods produce silicon ribbons which contain relatively high densities of structural defects, such as grain boundaries, twin boundaries and dislocations. In addition, small amounts of chemical impurities are introduced into the ribbons during growth from sources such as shaping dies (EFG), substrates (SOC, RTR), heat shields, etc.

Hydrogen Diffusion and Segregation in Alpha Iron ∑ 3 (111) Grain Boundaries

2015 ◽  
Author(s):  
Mohamed Hamza ◽  
Tarek M. Hatem ◽  
Dierk Raabe ◽  
Jaafar A. El-Awady
Keyword(s):  
Mechanical Properties ◽  
Grain Boundaries ◽  
Surface Segregation ◽  
Structural Integrity ◽  
Hydrogen Diffusion ◽  
Coincidence Site Lattice ◽  
Md Simulations ◽  
Hydrogen Diffusivity ◽  
Hydrogen Atoms ◽  
The Ideal

Polycrystalline material generally exhibits degradation in its mechanical properties and shows more tendency for intergranular fracture due to segregation and diffusion of hydrogen on the grain boundaries (GBs). Understanding the parameters affecting the diffusion and binding of hydrogen within GBs will allow enhancing the mechanical properties of the commercial engineering materials and developing interface dominant materials. In practice during forming processes, the coincidence site lattice (CSL) GBs are experiencing deviations from their ideal configurations. Consequently, this will change the atomic structural integrity by superposition of sub-boundary dislocation networks on the ideal CSL interfaces. For this study, the ideal ∑ 3 111 [110] GB structure and its angular deviations in BCC iron within the range of Brandon criterion will be studied comprehensively using molecular statics (MS) simulations. The clean GB energy will be quantified, followed by the GB and free surface segregation energies calculations for hydrogen atoms. Rice-Wang model will be used to assess the embrittlement impact variation over the deviation angles. The results showed that the ideal GB structure is having the greatest resistance to embrittlement prior GB hydrogen saturation, while the 3° deviated GB is showing the highest susceptibility to embrittlement. Upon saturation, the 5° deviated GB appears to have the highest resistance instead due to the lowest stability of hydrogen atoms observed in the free surfaces of its simulation cell. Molecular dynamics (MD) simulations are then applied to calculate hydrogen diffusivity within the ideal and deviated GB structure. It is shown that hydrogen diffusivity decreases significantly in the deviated GB models. In addition, the 5° deviated GB is representing the local minimum for diffusivity results suggesting the existence of the highest atomic disorder and excessive secondary dislocation accommodation within this interface.

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