scholarly journals Cadmium Chloride Assisted Re-Crystallisation of CdTe: The Effect on the CdS Window Layer

2015 ◽  
Vol 1738 ◽  
Author(s):  
Ali Abbas ◽  
Piotr Kaminski ◽  
Geoff West ◽  
Kurt Barth ◽  
WS Sampath ◽  
...  
Keyword(s):  
Cadmium Chloride ◽  
Density Functional ◽  
Treatment Time ◽  
Depth Profiling ◽  
Stacking Faults ◽  
Annealing Treatment ◽  
Cadmium Sulphide ◽  
Window Layer ◽  
Electrical Performance ◽  
Cell Efficiency

ABSTRACTThe cadmium chloride annealing treatment is an essential step in the manufacture of efficient thin film CdTe solar cells. In previous work we have shown that the primary effect of the treatment is to remove high densities of stacking faults from the as-deposited material. Use of density functional theory has shown that some of the higher energy stacking faults are hole traps. Removal of these defects dramatically improves cell efficiency. In this study we focus on the effect of the activation treatment on the underlying n-type cadmium sulphide layer. A range of techniques has been used to observe the changes to the microstructure as well as the chemical and crystallographic changes as a function of treatment parameters. Electrical tests that link the device performance with the micro-structural properties of the cells have also been undertaken. Techniques used include High Resolution Transmission Electron Microscopy (HRTEM) for sub-grain analysis, EDX for chemical analysis and XPS and SIMS for composition-depth profiling. By studying the effect of increasing the treatment time and temperature, we will show that the cadmium sulphide layer depletes to the point of complete dissolution into the absorber layer. We will also show that chlorine penetrates and decorates the grain boundaries in the cadmium sulphide. In addition we will show that chlorine builds up at the heterojunction and concentrates in voids at the cadmium telluride/cadmium sulphide interface. A combination of these effects damages the electrical performance of the solar cell.

The Effect of Annealing Treatments on Close Spaced Sublimated Cadmium Telluride Thin Film Solar Cells

2013 ◽  
Vol 1493 ◽  
pp. 147-152 ◽  
Author(s):  
J.M. Walls ◽  
A. Abbas ◽  
G. D. West ◽  
J.W. Bowers ◽  
P.J.M. Isherwood ◽  
...  
Keyword(s):  
Thin Film ◽  
Solar Cells ◽  
Cadmium Telluride ◽  
Cadmium Chloride ◽  
High Efficiency ◽  
Stacking Faults ◽  
Annealing Treatment ◽  
Complete Removal ◽  
Close Space Sublimation ◽  
Transmission Electron

ABSTRACTIt is well known that the cadmium chloride annealing treatment is an essential step in the manufacture of efficient thin film cadmium telluride solar cells. It has been recognized that the combination of annealing at ∼4000C together with the addition of cadmium chloride at the surface induces re-crystallisation of the cadmium telluride layer and also affects the n-type cadmium sulfide. We have applied advanced micro-structural characterization techniques to distinguish the effect of the annealing and the cadmium chloride treatments on the properties of the cadmium telluride deposited via close space sublimation (CSS) and relate these observations to device performance. Transmission electron microscopy (TEM) has shown a variation in stacking fault density with annealing temperature and annealing time. Stacking faults observed within the cadmium telluride grains in TEM were partially removed post annealing; these findings show that temperature alone has a role in the reduction of stacking faults. However, since we have previously observed almost complete removal of stacking faults with annealing in combination with cadmium chloride, the cadmium chloride is essential to defect removal and high efficiency cells.

Cadmium Chloride Assisted Re-Crystallization of CdTe: The Effect of Varying the Annealing Time

2014 ◽  
Vol 1638 ◽  
Author(s):  
A. Abbas ◽  
G. D. West ◽  
J.W. Bowers ◽  
P. M. Kaminski ◽  
B. Maniscalco ◽  
...  
Keyword(s):  
Cadmium Telluride ◽  
Cadmium Chloride ◽  
High Efficiency ◽  
Morphological Changes ◽  
Depth Profiling ◽  
Annealing Treatment ◽  
Photovoltaic Devices ◽  
Micro Structure ◽  
Transmission Electron ◽  
Chloride Treatment

ABSTRACTAlthough the cadmium chloride treatment is an essential process for high efficiency thin film cadmium telluride photovoltaic devices, the precise mechanisms involved that improve the cadmium telluride layer are not well understood. In this investigation we apply advanced micro-structural characterization techniques to study the effect of varying the time of the cadmium chloride annealing treatment on the micro-structure of cadmium telluride solar cells deposited by close spaced sublimation (CSS) and relate this to cell performance. A range of techniques has been used to observe the morphological changes to the micro-structure as well as the chemical and crystallographic changes as a function of treatment parameters. Electrical tests that link the device performance with the micro-structural properties of the cells have also been undertaken. Techniques used include Transmission Electron Microscopy (TEM) for sub-grain analysis and XPS for composition-depth profiling. The study provides a new insight in to the mechanisms involved in the initiation and the subsequent complete re-crystallization of the cadmium telluride layer.

Ab Initio Calculation of Mechanical Properties of Stacking Fault in 3C-SiC: Effect of Stress and Doping

2012 ◽  
Vol 717-720 ◽  
pp. 415-418
Author(s):  
Yoshitaka Umeno ◽  
Kuniaki Yagi ◽  
Hiroyuki Nagasawa
Keyword(s):  
Mechanical Properties ◽  
Ab Initio ◽  
Density Functional ◽  
Stacking Faults ◽  
Single Layer ◽  
Local Strain ◽  
Density Functional Theory Calculations ◽  
Stacking Fault ◽  
Functional Theory ◽  
N Doping

We carry out ab initio density functional theory calculations to investigate the fundamental mechanical properties of stacking faults in 3C-SiC, including the effect of stress and doping atoms (substitution of C by N or Si). Stress induced by stacking fault (SF) formation is quantitatively evaluated. Extrinsic SFs containing double and triple SiC layers are found to be slightly more stable than the single-layer extrinsic SF, supporting experimental observation. Effect of tensile or compressive stress on SF energies is found to be marginal. Neglecting the effect of local strain induced by doping, N doping around an SF obviously increase the SF formation energy, while SFs seem to be easily formed in Si-rich SiC.

scholarly journals An estimation on the mechanical stabilities of SAMs by low energy Ar+ cluster ion collision

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Y. Tong ◽  
G. R. Berdiyorov ◽  
A. Sinopoli ◽  
M. E. Madjet ◽  
V. A. Esaulov ◽  
...  
Keyword(s):  
Electron Irradiation ◽  
Photoelectron Spectroscopy ◽  
Density Functional ◽  
Crystal Surface ◽  
Depth Profiling ◽  
Low Energy ◽  
Cross Linking ◽  
Xps Spectra ◽  
Self Assembled ◽  
The Stability

AbstractThe stability of the molecular self-assembled monolayers (SAMs) is of vital importance to the performance of the molecular electronics and their integration to the future electronics devices. Here we study the effect of electron irradiation-induced cross-linking on the stability of self-assembled monolayer of aromatic 5,5′-bis(mercaptomethyl)-2,2′-bipyridine [BPD; HS-CH2-(C5H3N)2-CH2-SH] on Au (111) single crystal surface. As a refence, we also study the properties of SAMs of electron saturated 1-dodecanethiol [C12; CH3-(CH2)11-SH] molecules. The stability of the considered SAMs before and after electron-irradiation is studied using low energy Ar+ cluster depth profiling monitored by recording the X-ray photoelectron spectroscopy (XPS) core level spectra and the UV-photoelectron spectroscopy (UPS) in the valance band range. The results indicate a stronger mechanical stability of BPD SAMs than the C12 SAMs. The stability of BPD SAMs enhances further after electron irradiation due to intermolecular cross-linking, whereas the electron irradiation results in deterioration of C12 molecules due to the saturated nature of the molecules. The depth profiling time of the cross-linked BPD SAM is more than 4 and 8 times longer than the profiling time obtained for pristine and BPD and C12 SAMs, respectively. The UPS results are supported by density functional theory calculations, which show qualitative agreement with the experiment and enable us to interpret the features in the XPS spectra during the etching process for structural characterization. The obtained results offer helpful options to estimate the structural stability of SAMs which is a key factor for the fabrication of molecular devices.

3D Distributions of Chlorine and Sulphur Impurities in a Thin-Film Cadmium Telluride Solar Cell

MRS Advances ◽  
2018 ◽  
Vol 3 (56) ◽  
pp. 3287-3292 ◽  
Author(s):  
Thomas A. M. Fiducia ◽  
Kexue Li ◽  
Amit H. Munshi ◽  
Kurt Barth ◽  
Walajabad S. Sampath ◽  
...  
Keyword(s):  
Cadmium Telluride ◽  
Cadmium Chloride ◽  
High Efficiency ◽  
Cadmium Sulphide ◽  
Diffusion Profile ◽  
Lattice Diffusion ◽  
Three Dimensions ◽  
Device Performance ◽  
Extended Defects ◽  
Cdte Solar Cells

ABSTRACTA cadmium chloride activation treatment is essential for the production of high efficiency cadmium telluride (CdTe) solar cells. However, the effects of the treatment on the distributions of chlorine and sulphur within the device are not fully understood. Here, the detailed locations of chlorine and sulphur in a treated CdTe cell are determined in three dimensions by high resolution dynamic SIMS measurements. Chlorine is found to be present in grain boundaries, grain interiors, extended defects within the grain interiors, at the front interface, and in the cadmium sulphide layer. In each of these regions, the chlorine is likely to have significant effects on local electronic properties of the material, and hence overall device performance. Sulphur is found to have a U-shaped diffusion profile within CdTe grains, indicating a mixed grain boundary and lattice diffusion regime.

Experimental and DFT computational studies of L-alanine cadmium chloride crystals

2016 ◽  
Vol 05 (01) ◽  
pp. 1630001
Author(s):  
I. Cicili Ignatius ◽  
S. Dheivamalar ◽  
K. Kirubavathi ◽  
K. Selvaraju
Keyword(s):  
Cadmium Chloride ◽  
Density Functional ◽  
Nonlinear Optical ◽  
Energy Gap ◽  
X Ray Diffraction ◽  
Monoclinic System ◽  
Functional Theory ◽  
Bond Angles ◽  
Cell Parameters ◽  
B3lyp Calculation

In this work, we report the combined experimental and theoretical study on molecular structure and vibrational spectra of nonlinear optical crystal L-alanine cadmium chloride (LACC). The single X-ray diffraction studies have revealed that the compound crystallizes in monoclinic system C2 space group with cell parameters [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text]. FTIR and Raman spectra of the nonlinear optical materials LACC have been recorded and analyzed. The optimized geometric bond length and bond angles are obtained with the help of density functional theory (DFT) (B3LYP) calculation. The optimized geometric bond lengths and bond angles obtained by using DFT show good agreement with the experimental data. Using the natural bond orbital analysis the electronic effect and hydrogen bonding were confirmed. The HOMO–LUMO energy gap and the first order hyperpolarizability were calculated and it supports the nonlinear optical activity of LACC crystal.

Systematic first principles calculations of the effects of stacking faults defects on the 4H-SiC band structure

2010 ◽  
Vol 1246 ◽  
Author(s):  
Massimo Camarda ◽  
pietro delugas ◽  
Andrea Canino ◽  
Andrea Severino ◽  
nicolo piluso ◽  
...  
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Stacking Faults ◽  
Perfect Crystal ◽  
First Principles Calculations ◽  
Electronic Band ◽  
Functional Theory ◽  
Experimental Findings ◽  
Electronic Band Structures ◽  
Formation Energies

AbstractShockley-type Stacking faults (SSF) in hexagonal Silicon Carbide polytypes have received considerable attention in recent years since it has been found that these defects are responsible for the degradation of forward I-V characteristics in p-i-n diodes. In order to extend the knowledge on these kind of defects and theoretically support experimental findings (specifically, photoluminescence spectral analysis), we have determined the Kohn-Sham electronic band structures, along the closed path Γ-M-K-Γ, using density functional theory. We have also determined the energies of the SSFs with respect to the perfect crystal finding that the (35) and (44) SSFs have unexpectedly low formation energies, for this reason we could expect these two defects to be easily generated/expanded either during the growth or post-growth process steps.

DFT Study of the CO Poisoning Effects on PdxCu1-x (110) Surface

2012 ◽  
Vol 15 (3) ◽  
pp. 151-156
Author(s):  
Ernesto López-Chávez ◽  
Alberto García-Quiroz ◽  
Yesica A. Peña-Castañeda ◽  
Fray De Landa Castillo-Alvarado ◽  
Gerardo Cabañas-Moreno ◽  
...  
Keyword(s):  
Density Functional ◽  
Proton Exchange Membrane ◽  
Co Adsorption ◽  
State Density ◽  
Proton Exchange ◽  
Pt Catalyst ◽  
Poisoning Effect ◽  
Cell Efficiency ◽  
Functional Density Theory ◽  
Exchange Membrane

CO contaminants play a significant role in modifying the performance of proton exchange membrane fuel cells (PEMFC). Pt is probably the most common catalyst being used today to absorb CO in the PEMFC, yet recent studies have shown that the use of Pd alloys such as Pd-Cu can increase the fuel cell efficiency versus a pure Pt catalyst. In this work, we examine the adsorption of CO onto PdxCu1-x (110) surfaces, with different values of x, in order to improve the CO tolerance. Understanding how molecules interact with such surfaces is the first step in understanding catalytic reactions. The study here presented was done using CASTEP, a computational code based on the plane-wave pseudopotential method of functional density theory. The surface structure of PdxCu1-x (110) was optimized and then the state density-functional, the repulsion energies and the chemisorption for CO on PdxCu1-x(110) were calculated. The results indicate that chemisorption energies of CO on PdxCu1-x are highly dependent on the concentration x of the alloy. In addition, density of states analysis indicate that the poisoning effect is partially due to the loss of Pd-Cu(d) electrons upon CO adsorption.

Sign in / Sign up

Export Citation Format

Share Document