DEVELOPMENT OF NON-TOXIC AND LATTICE MATCHED BUFFER LAYER FOR CZTS SOLAR CELLS
Presentation by: Faiazul Haque (P67226)
Supervisor: Prof. Dr. Nowshad AminCo-Supervisor: Prof. Dato’ Dr Kamaruzzaman
Sopian
M.Sc VIVA Presentation
Solar Energy Research InstituteThe National University of Malaysia
(@Universiti Kebangsaan Malaysia, UKM)
Outline Introduction
- Energy, Environment & Solar Cells
- Classification of solar cells
- CZTS Schematic & Buffer Layer Literature Review Problem Statement Objectives Methodology
- Numerical Analysis by AMPS-1D
- Practical Fabrication Results and Discussions
- Part 1: Numerical simulation by AMPS 1D
- Part 2: ZnS Thin Films Characterization
- Part 3: n-ZnS/p-CZTS Full Device Results Conclusion2
3
• Carbon dioxide emission• Global warming
• Energy demand is ever increasing• Main energy production is by fossil fuels
Energy versus Environment
Renewable Energy SourcesSolar
A solar cell is a semiconductor device designed to convert sunlight into electricity. The conversion of light into electricity in a solar cell is called the photovoltaic (PV) effect. Photovoltaic stands for photo, meaning “light”, and voltaic, meaning “electricity”.
INTRODUCTION: ENERGY, ENVIRONMENT & SOLAR CELLS
Wind
Geothermal
Biomass
Wave
Among all the renewable energy resources, solar energy is considered the most consistent and abundant renewable energy source.
PV System → Solar Cell
Solar CellsSolar Cells
First Generation:(Mainly Si, 200 - 600
µm thick)
First Generation:(Mainly Si, 200 - 600
µm thick)
Third Generation:Organic / Hybrid Solar Cells (Dye Sensitized Solar Cell, Quantum
dot, Tandem, Perovskite etc.)
Third Generation:Organic / Hybrid Solar Cells (Dye Sensitized Solar Cell, Quantum
dot, Tandem, Perovskite etc.)
Classification of Solar Cells
Second Generation:Thin Film Solar Cells: 1.5 - 5 µm thick (a-Si,
CdTe, CIS, CIGS, CZTS etc)
Second Generation:Thin Film Solar Cells: 1.5 - 5 µm thick (a-Si,
CdTe, CIS, CIGS, CZTS etc)
CZTS → Cu2ZnSnS4
Group I2-II-IV-VI4 p-type quarternarycompound semiconductor. Optimal direct bandgap energy (1.4 ev - 1.5 eV) High absorption coefficient. (α > 1 x 104 cm-1) Has similar material properties like CIGS ( CuInxGa1-xS(Se)2 ) Abundant in nature (Cu=50 ppm, Zn=75 ppm, Sn=2.2 ppm, S=260 ppm compared to In=0.049 ppm and Se=0.05 ppm) Non toxic and Inexpensive
CZTS Schematic & Buffer Layer
Substrate Configuration
Attributes of a good buffer layer
1. Good lattice matching property with absorber layer – enables the formation of interface with low defect density.
2. High transparency and wide bandgap material: to allow photons to pass through to the absorber layer.
3. Optimum thickness (around 50 nm) to avoid short circuit effects.
4. High conductivity to minimize carrier loss.
5. Free from toxic elements.
Roles of the buffer layer
• Serves as a heterojunction partner for p-CZTS layer. Serves as a protection layer during TCO sputtering. Insulates pin holes to avoid shunting.
Literature Review:Timeline of CZTS Development
6
1967
1967: CZTS single crystal was synthesized and
analyzed for the first time
1988 1996 1997 1999 2006 2008 2010 2013
1988: K. Ito and T. Nakazawa confirmed suitability of CZTS by Atomic Beam Sputtering
technique
1996: Katagiri et al. first time fabricated CZTS on SLG by E-B evaporation technique followed
by sulfurization η = 0.66% [SLG/Mo/CZTS/CdS/AZO]1997: Friedlmeier et al.
achieved η = 2.3% by using the same structure & technique of
Katagiri’s group
1999: Katagiri et al. used Mo coated SLG &
broke the previous record with η = 2.63%
2006: co-sputtering technique was introduced
by K. Jimbo et al and achieved η= 5.74%
2008: Katagiri et al. reported η= 6.77%
efficiency by RF co-sputtering followed by
sulfurization
2010: IBM reported η=9.6% with CZTSSe by using the wet process/non vacuum
process
2013: Todorov et al. reported η=11.1% with
CZTSSe using spin coating technique.
So far a conversion efficiency of 12.6% has
been achieved using a CZTSSe absorber
layer by hydrazine chemical process.In December 2014, CZTS
solar cell efficiency reached
8.8% by Toyota Centre R&D
using co-sputtering
technique
Still there are challenges!!!
Literature Review
CdS: Conventional buffer layer.
Efficiency achieved: more than 12.6% (on CZTS absorber)
But has the following disadvantages: Presence of toxic element
Cadmium. Bandgap ~ 2.45 eV. Limits the blue response of the
photovoltaic cells. CBD (Chemical Bath Deposition)
is not desired in commercialization stage, as it requires tedious and costly waste disposal plan and treatment.
ZnS: Prospective candidate
as an alternative buffer layer.
Efficiency achieved: 18.6% (on CIGS absorber)
Advantages: Non toxic layer. Bandgap ~ 3.1 eV – 3.7 eV
(Higher than CdS). Enhances the blue response of
the photovoltaic cells. Relatively cheaper and
abundant. Deposition by sputtering is
suitable for in-line vacuum large scale commercialized production.
Possible compound semiconductors as buffer layer are: CdS, ZnS, ZnSe, In2S3, CdSe, ZnxCd1-xS etc.
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Problem Statement:
The presence of toxic Cadmium (Cd) in the buffer layer will raise questions regarding the environmental risk.
This technology will face a marketing problem due to legal regulations of Cd usage in electrical and electronic devices in different countries.
Due to the relatively smaller bandgap of CdS, there is considerable amount of photon loss.
CdS is commonly deposited by Chemical Bath Deposition (CBD) technique, which is tedious and not desired for commercialization stage.
If the CdS can be replaced by another material having higher bandgap, the absorption loss can also be minimized and hence can contribute to an improved cell efficiency.8
Objectives
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SLG Substrate
Metal Back Contact (Mo)
p type absorber layer(CZTS)
n type buffer layer(CdS)
TCO Window Layer(ZnO:Al)
Grid
n type buffer layer(ZnS)
Conventional Buffer
Alternative Buffer
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Main Objective:To assess the
performance of ZnS as a non-
toxic and lattice matched buffer layer for CZTS
solar cells
Objective 1:
To analyze the performance of n-ZnS and p-CZTS
thin film solar cells by AMPS-1D, as a feasibility study or
theoretical validation.
Objective 2:
To fabricate, characterize and optimize ZnS thin films deposited by RF magnetron sputtering
technique and study the effects of different
annealing temperatures.Objective 3:
To fabricate complete basic n-ZnS and p-CZTS
solar cell and analyze the
performance.
Methodology:Numerical Analysis by AMPS-1D
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1. AMPS-1D is an abbreviation for “Analysis of Microelectronic and Photonic Structures,”.
2. In general AMPS 1D is a free software and widely used for solar cell and detector design, material parameter sensitivity studies, and parameter extraction.
3. The program has been successfully used by 70 groups to study detector and solar cells.
4. It has several features which make it especially attractive: It can analyze the transport in a variety of crystalline, polycrystalline,
or amorphous solar-cell materials, and device structures including homojunction, heterojunction, or multijunction solar cells and detectors.
It also has a very flexible plotting program, so, user can generate output plots such as:
1. J-V curves, 2. Spectral response, 3. Band diagrams, 4. Carrier concentrations and 5. Currents, and recombination profiles under various
bias conditions.
Parameters n-ZnO:Al
n-ZnS p-CZTS
Thickness, W (μm) 0.2 0.03-0.08
1-4
Dielectric ratio, ε/εo 9.0 10 10Electron mobility, μn (cm2/Vs)
100 100 100
Hole mobility, μp (cm2/Vs) 25 25 25
Carrier concentration, n/p (cm-3)
1018 9.0×1017 2×1015
Bandgap, Eg (eV) 3.30 3.10-3.40
1.40
CB Density of states, NC (cm-3)
2.2×1018 1.5×1018 2.2×1018
VB Density of states, NV (cm-3)
1.8×1019 1.8×1018 1.8×1019
Electron affinity, χ (eV) 4.60 4.50 4.10
The main aim of numerical simulation of solar cells is to validate its performance with respect to
various input parameters and to observe the trend
Methodology:Numerical Analysis by AMPS-1D
Numerical Simulation by AMPS 1D
Variation of CZTS absorber thickness
Variation of ZnS buffer thickness
Variation of ZnS buffer bandgap
Variation of operating temp.
Analysis & Optimization of the simulated parameters
To accomplish objective 1
Methodology: Practical Fabrication
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Sputter ZnS on SLG substrates
Variation of growth temp. (RT – 400˚C)
Anneal each films at (300˚C, 400˚C & 500˚C)
Anneal each films at (300˚C, 400˚C & 500˚C)
Characterization of the as grown and annealed samples
Optimization of the deposition and annealing conditions
Full device fabrication with optimized buffer layer parameters
Variation of RF power (40W – 80W)
To accomplish objective 3
To accomplish objective 2
Methodology: Practical Fabrication
Results and Discussion:
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Part 1• Numerical Simulation to Validate ZnS as
Alternative Buffer
Part 2
• ZnS Thin Films Deposition & Characterization• Effect of Growth Temp.• Effect of RF Power
Part 3• n-ZnS/p-CZTS Complete Solar Cell
Fabrication & Characterization
Results & Discussion:Numerical Simulation
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Ultra thin absorber layer is
sufficient to absorb the solar
spectrum.
Absorber layer thickness variation
Variation of operating temp.
Additional thermal energy
gained by the electrons
causes to recombine before
reaching the depletion region.
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Results & Discussion:Numerical Simulation
Buffer layer thickness variation
Thinner buffer layer allows
the majority of the photons
to be transmitted towards
the absorber layer.
Buffer layer bandgap variation
Bandgap engineering can be
employed to tune the
bandgap according to the
subsequent TCO layer.
Optimized bandgap:
3.10 – 3.25 eV
Obtained final J-V curve considering the optimized parameters
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Part 1• Numerical Simulation to Validate ZnS as
Alternative Buffer
Part 2
• ZnS Thin Films Deposition & Characterization• Effect of Growth Temp.• Effect of RF Power
Part 3• n-ZnS/p-CZTS Complete Solar Cell
Fabrication & Characterization
Objective 1:Accomplished
Results and Discussion:
As grown (RT – 400˚C)
Results & Discussion: XRD
Grown at RT + AnnealedGrown at 100˚C + AnnealedGrown at 200˚C + AnnealedGrown at 300˚C + AnnealedGrown at 400˚C + Annealed
Growth temperature plays a significant
role in the crystallinity of the ZnS films
@ various growth temp. + subsequently annealed
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Results & Discussion: XRD
As Grown (40 W – 80 W)Grown at 60 W + AnnealedGrown at 70 W + AnnealedGrown at 80 W + Annealed
Highest RF power produced
better crystalline films.
@ different RF Powers + subsequently annealed
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Results & Discussion: UV-Vis
Average transmittance of over 80%
confirming excellent photovoltaic
properties for buffer layer.
Overall bandgap increased from
3.1 eV to 3.8 eV with the increase
of substrate temp.
TransmittanceBandgap
@ various growth temp.
After annealing, very small change was observed in the bandgap.
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Results & Discussion: UV-Vis
Average transmittance of over 80%
recorded.The bandgap remained in the
range of 3.20 eV to 3.45 eV.
TransmittanceBandgap
@ different RF Powers
After annealing, very negligible amount of change was observed in the bandgap.
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T=100 T=200 T=300
T=400
T=RT
Fig: Roughness trend w.r.t. substrate temperature.
Results & Discussion: AFM
Roughness values remained in the range of
4 nm to 14 nm which is acceptable for buffer
layer applications.
@ various growth temp.
23Fig: Roughness trend w.r.t. RF Power.
RF40 RF50 RF60 RF70
RF80
Roughness values remained in the range of
4 nm to 25 nm which is acceptable for buffer
layer applications.
Results & Discussion: AFM@ different RF Powers
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10
0˚C
30
0˚C
40
0˚C
Subsequently annealedat 500˚C
Subsequently annealedat 500˚C
Subsequently annealedat 500˚C
The grain size of the annealed films are
found to be bigger along with a compact &
fine grained morphology.
Results & Discussion: SEM@ various growth temp. + subsequently annealed
25
60
W7
0 W
80
W
Subsequently annealedat 500˚C
Subsequently annealedat 500˚C
Subsequently annealedat 500˚C
Results & Discussion: SEM
With the increasing RF power, the grains
became more closely packed and possessed
spherical shapes compared to the films
grown at lower RF power.
@ different RF Powers + subsequently annealed
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1. Conductivity Type: n type
2. Bulk Carrier Density: 1012 cm-3
3. Surface Carrier Density: 107 cm-2
4. Highest Carrier Concentration: 400˚C
5. Lowest Resistivity: 300˚C
Fig. Carrier Concentration and Resistivity w.r.t substrate temp.
Results & Discussion: HALL Measurements@ various growth temp.
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1. Conductivity Type: n type
2. Bulk Carrier Density: 1012 cm-3
3. Surface Carrier Density: 107 cm-2
Fig. Carrier Concentration and Resistivity w.r.t RF Power.
Results & Discussion: HALL Measurements@ different RF Powers
Results and Discussion:
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Part 1• Numerical Simulation to validate ZnS as
alternative buffer
Part 2
• ZnS Thin Films Deposition & Characterization• Effect of Growth Temp.• Effect of RF Power
Part 3• n-ZnS/p-CZTS Complete Solar Cell
Fabrication & Characterization
Objective 1:Accomplished
Objective 2:Accomplished
Results and Discussion: Full Working Device Deposition
SLG Substrate
Metal Back Contact (Mo)
p type absorber layer(CZTS)
TCO Window Layer(ZnO:Al)
FC
n type buffer layer(CdS)
Cell Voc (Volts)
Jsc (mA/c
m2)
FF η (%)
Cell 1 0.075 22.092 0.278 0.46 %
Cell 2 0.4 5.875 0.341 0.71 %
CZTS/CdS
Cell ZnS deposition parameters
Annealing parameters
Growth Temp.
(˚C)
RF (W)
Temp. (˚C)
Time (min)
Cell 1 100 80 N.A. N.A.Cell 2 300 80 N.A. N.A.Cell 3 RT 80 300 20
SLG Substrate
Metal Back Contact (Mo)
p type absorber layer(CZTS)
n type buffer layer(ZnS)
TCO Window Layer(ZnO:Al)
FC
CZTS/ZnSCell Voc
(Volts)Jsc
(mA/cm2)
FF η (%)
Cell 1 0.51 7.44 0.43 1.63 %
Cell 2 0.57 6.69 0.45 1.72 %
Cell 3 0.4 5.88 0.27 0.64 %
The J-V curves clearly show the formation of a p-n junction any solar cell should have and it is only a matter of optimization of many layers or deposition parameters to improve the curve as well as the efficiency.
Final Optimized Parameters:
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Deposition Parameters ConditionTarget ZnS (99.99% pure)Substrate TemperatureRF powerBase PressureWorking Pressure
300°C80 Watt
6.2 × 10-5 Torr4.0 × 10-2 Torr
Sputtering GasAnnealing TimeAnnealing Temperature
Pure argon (5 SCCM)20 minutes
300°C
Results and Discussion:
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Part 1• Numerical Simulation to validate ZnS as
alternative buffer
Part 2
• ZnS Thin Films Deposition & Characterization• Effect of Growth Temp.• Effect of RF Power
Part 3• n-ZnS/p-CZTS Complete Solar Cell
Fabrication & Characterization
Objective 1:Accomplished
Objective 2:Accomplished
Objective 3:Accomplished
CONCLUSION
Objective 1 • η = 14.49% (Voc=0.81 V, Jsc=28.85 mA/cm2, FF=0.67) is achievable with ZnS/CZTS solar cell
Objective 2
• Higher growth temperature yielded better quality films• Optimized growth temperature: 300 °C• Optimized RF Power: 80 Watt• Post deposition annealing temperature has significant effect
on the structural, optical and electrical properties • Optimized annealing temperature: 300 °C.
For Al/ZnO:Al/ZnS/CZTS/Mo solar cell• The highest conversion efficiency =1.72 % • Voc = 0.57 V• Jsc = 6.69 mA/cm2
• Fill factor = 0.45
Objective 3
This study has investigated the potentials of ZnS as an alternative non-toxic and lattice matched buffer layer that opened up the usage
for CZTS solar cells as a result of theoretical and practical investigation, which can play a crucial role in the commercialization
process.
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PUBLICATIONSJournals:
[1] F. Haque, K.S. Rahman, M.A. Islam, M.J. Rashid, M. Akhtaruzzaman, M.M. Alam, Z.A. Alothman, K. Sopian & N. Amin. 2014. Growth Optimization of ZnS Thin Films by RF Magnetron Sputtering as Prospective buffer Layer in Thin Film Solar Cells. Chalcogenide Letters 11(4): 189-197.[ISI: Q3: IF=1.184]
[2] P. Chelvanathan, Y. Yusoff, F. Haque, M. Akhtaruzzaman, M.M. Alam, M.J. Rashid, K. Sopian & N. Amin. 2014. Growth and characterization of RF-sputtered ZnS thin film deposited at various substrate temperatures for photovoltaic application. Applied Surface Science. In Press, Corrected Proof. (Available online: 11 Oct 2014). doi:10.1016/j.apsusc.2014.08.155 [ISI: Q1: IF=2.538]
[3] M.A. Islam, K.S. Rahman, F. Haque, M. Akhtaruzzaman, M.M. Alam, Z.A. Alothman, K. Sopian & N. Amin. 2014. Properties of Low Temperature Vacuum Annealed CZTS Thin Films Deposited on Polymer Substrate. Chalcogenide Letters 11(5): 233-239. [ISI: Q3: IF=1.184]
[4] F. Haque, K.S. Rahman, N.A. Khan, M.A. Islam & N. Amin. 2014. Analysis of the Structural and Optical Properties of Thermally Evaporated Zinc Sulphide (ZnS) Thin Films for Photovoltaic Application. Australian Journal of Basic and Applied Sciences 8(19): 264-267. [SCOPUS]
International Conferences:
[1] F. Haque, N.A. Khan, K.S. Rahman, M.A. Islam, M.M. Alam, K. Sopian & N. Amin. 2014. Prospects of Zinc Sulphide as an Alternative Buffer Layer for CZTS Solar Cells from Numerical Analysis. 8th International Conference on Electrical and Computer Engineering (ICECE 2014) Dhaka, Bangladesh. In IEEE Xplore Digital Library. Page(s): 504-507. DOI: 10.1109/ICECE.2014.7026855
[2] F. Haque, K.S. Rahman, M.A. Islam, P. Chelvanathan, T.H. Chowdhury, M.M. Alam & N. Amin. 2013. A Comparative Study of ZnS Thin Films Grown by Thermal Evaporation and Sputtering. IEEE Student Conference on Research and Development (SCOReD 2013), Putrajaya, Malaysia. In IEEE Xplore Digital Library. Page(s): 260-264. DOI: 10.1109/SCOReD.2013.7002584
PUBLICATIONS
[3] F. Haque, K.S. Rahman, N.A. Khan, M.A. Islam, M. J. Rashid, M. Salim, M. Akhtaruzzaman, M.M. Alam & N. Amin. 2014. A Comprehensive Study on Undoped and In-doped ZnS Thin Films Prepared by Co-sputtering Technique. Poster Presentation in International Conference on Electronic Materials and Nanotechnology for Green Environment (ENGE 2014), Jeju, Korea.
[4] K.S. Rahman, F. Haque, N.A. Khan, M.A. Islam, M.M. Alam, Z.A. ALOthman, K. Sopian & N. Amin. 2014. Influence of Thermal Annealing on CdTe Thin Film Deposited by Thermal Evaporation Technique. 3rd International Conference on the Developments in Renewable Energy Technology (ICDRET'14), Dhaka, Bangladesh. In IEEE Xplore Digital Library. Page(s): 1-4. DOI: 10.1109/ICDRET.2014.6861722
[5] K.S. Rahman, F. Haque, M.A. Islam, M.M. Alam, Z.A. Alothman & N. Amin. 2013. Effect of Growth Techniques on the Properties of CdTe Thin Films for Photovoltaic Application. IEEE Student Conference on Research and Development (SCOReD 2013), Putrajaya, Malaysia. In IEEE Xplore Digital Library. Page(s): 265-268. DOI: 10.1109/SCOReD.2013.7002585
[6] K.S. Rahman, F. Haque, N.A. Khan, M.A. Islam, M.M. Alam, M. Akhtaruzzaman, K. Sopian & N. Amin. 2014. Properties of Cu Incorporated CdTe Thin Films for Photovoltaic Application. Poster Presentation in International Conference on Electronic Materials and Nanotechnology for Green Environment (ENGE 2014), Jeju, Korea.
[7] N.A. Khan, K.S. Rahman, F. Haque, N. Dhar, M.A. Islam, M. Akhtaruzzaman, K. Sopian & N. Amin. 2014. Design Optimization of CdTe Thin Film Solar Cells from Numerical Analysis. 8th International Conference on Electrical and Computer Engineering (ICECE 2014) Dhaka, Bangladesh. In IEEE Xplore Digital Library. Page(s): 508-511. DOI: 10.1109/ICECE.2014.7026862
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REFERENCES1. Siebentritt, S., 2004. Alternative bu ers for chalcopyrite solar cells. ff Sol. Energy 77: 767.
2. Fella, C.M., Stuckelberger, J.A., Uhl, A.R., Romanyuk, Y.E. and Tiwari, A.N. 2013. Influence of annealing conditions on non-vacuum deposited Cu2ZnSn(S,Se)4 absorber layers for thin film solar cells. Poster Presented at MRS Spring Meeting, San Francisco.
3. Wadia, C., Alivisatos, A.P. and Kammen, D.M. 2009. Materials availability expands the opportunity for large-scale photovoltaics deployment. Environ. Sci. Technol. 43 (6): 2072-2077.
4. Haque, F., Rahman, K.S., Islam, M.A., Rashid, M.J., Akhtaruzzaman, M., Alam, M.M., Alothman, Z.A., Sopian, K. and Amin, N. 2014. Growth Optimization of ZnS thin films by RF magnetron sputtering as prospective buffer layer in thin film solar cells. Chalcogenide Letters 11: 189-197.
5. Katagiri, H., Saitoh, K., Washio, T., Shinohara, H., Kurumadani, T. and Miyajima, S. 2001. Development of thin film solar cell based on Cu2ZnSnS4 thin films. Solar Energy Materials Solar Cells. 65: 141-148.
6. Katagiri, H., Jimbo, K., Yamada, S., Kamimura, T., Maw, W.S., Fukano, T., Ito, T. and Motohiro, T. 2008. Enhanced Conversion Efficiencies of Cu2ZnSnS4-Based Thin Film Solar Cells by Using Preferential Etching Technique. Appl. Phys. Express. 1 (4).
7. Jimbo, K., Kimura, R., Kamimura, T., Yamada, S., Maw, W.S., Araki, H., Oishi, K. and Katagiri, H. 2007. Cu2ZnSnS4-type thin film solar cells using abundant materials. Thin Solid Films. 515: 5997-5999.
8. Ito, K. and Nakazawa, T. 1988. Electrical and optical properties of stannite-type quaternary semiconductor thin films. Jpn. J. Appl. Phys. 27: 2094-2097.
9. Martin Green. 1982. Solar cells operating principles, technology, and system applications. New Jersey: Prentice-Hall.
10. Shahi, A., Chelvanathan, P., Hossain, M.I., Zaman, M., Sopian, K. and Amin, N. 2012. Performance Analysis of Cu2ZnSnS4 (CZTS) Solar Cell By Solar Cell Capacitance Simulator (SCAPS). Proceedings of The 22nd International Photovoltaic Science and Engineering Conference.
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12. Hwang, D.H., Ahn, J.H., Hui, N., Hui, K.S. and Son, Y.G. 2012. Structural and optical properties of ZnS thin films deposited by RF magnetron sputtering. Nanoscale Res Lett. 7: 26.
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Thank You….
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FUTURE WORK
1. Effect of Operating Pressure, Ar flow rate, etc can be varied to see their effects on the films.
2. Metal doping effects on the properties of ZnS thin films can be studied.
3. Prospects of Hydrogenated and Oxygenated ZnS (O,H) can be studied.
4. Variation on the duration of annealing can be explored.
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AMPS-1D To evaluate device performance with respect to various
input parameters. All the numerical programs used for modeling the thin film
solar cells work by solving the two basic semiconductor equations :
(i) Poisson’s equation for the distributions of (a) electric field (φ) inside the device.
(ii) the equation of continuity for conservation of (b) electrons and (c) holes current.
The physics of device transport can be achieved by solving these three governing equations (indicated by a, b, & c) along with the appropriate boundary conditions.
39
DRAWBACKS OF AMPS-1D AMPS-1D is a free software. It is not perfect as it only uses few basic
equations which doesn’t allow to manipulate many phenomena. Different type of defects cannon be included in the simulation, such
as anti-site, vacancy, mismatch, interface etc. It results in only ideal cases under standard condition most of the
times. May provide unrealistic results. During practical fabrication process, loss mechanism or generation-
recombination happen which is not possible to include in AMPS-1D. It has discreet grid points instead of being continuous. The objective of performing the simulation is to acquire knowledge on the
trend of the output parameters with respect to other parameters of the solar cells. The values of output parameters derived from the simulators are not necessary to believe strictly but the trend is much more important.
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BASIC EQUATIONS