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Characterization of Al-doped Conductive Layer of ZnO for Thin
Film Solar Cell
Presenting by:
Mohammad Shakil Khan3rd BatchExam Roll: 409, Reg. No: HA-297
OVERVIEW OF THIS PRESENTATION
Objective of the Thesis ZnO Layer Conductive Layer: AZO Methodology: Literature Review AZO Preparation: Sol-gel Method AZO Preparation Steps
i
OVERVIEW OF THIS PRESENTATION
Experimental Layer PreparationGlass Substrate Sample Slide Cleaning AZO Solution Preparation Magnetic Stirring of the Solution Deposition & Spin Coating of the Sample
Slides Ageing using OvenDrying in Ambient TemperatureAnnealing for DensificationPreparation Completion ii
OVERVIEW OF THIS PRESENTATION
AZO Characterization Thickness Measurement• Testing Preparation - Wet Etching Process• HNO3 Solution• Etching the Substrates• Testing• Result• Observation
Surface Morphology Test• Testing• Result• Observation iii
OVERVIEW OF THIS PRESENTATION
Hall Effect Measurement• Testing• Result• I-V Curve• Observation
Future Work Scope
iv
OBJECTIVE OF THIS THESIS
Observe technology for improving conductivity by Al doping on ZnO layer
Observe the layer thickness and relative characteristical change in the substrate
Identify dopant material requirement for optimization of layer resistivity
1
OBJECTIVE OF THIS THESIS
Impact of deposition on a fixed range of substrates
Observing affect of
surface roughness produced at fixed temperatures
2
ZnO LAYER
II-VI compound semiconductors
Wurtzite Crystal
Structure
Large band gap (Eg=3.37ev)
Large excitation energy of 60 meV
Source: https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwizu6PsuNTKAhVTj44KHcm6D7wQjhwIBQ&url=http%3A%2F%2Fpubs.rsc.org%2Fen%2Fcontent%2Farticlehtml%2F2013%2Fdt%2Fc3dt51578h&psig=AFQjCNFtdQPZyTVEjOzaTVhKcXUeifhc9Q&ust=1454343198573957
3
ZnO LAYER
High optical transmittance in the visible region
Blocks 95% of all UV radiation
Impurity doped ZnO has Good transparent conducting oxide (TCO) characteristics
Good electrical conductivity and low optical loss Source: https://www.google.com/url?
sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwizu6PsuNTKAhVTj44KHcm6D7wQjhwIBQ&url=http%3A%2F%2Fpubs.rsc.org%2Fen%2Fcontent%2Farticlehtml%2F2013%2Fdt%2Fc3dt51578h&psig=AFQjCNFtdQPZyTVEjOzaTVhKcXUeifhc9Q&ust=1454343198573957
4
CONDUCTIVE LAYER: AZO
Doped binary compounds, Composed of Al and Zn, common and inexpensive materials
Deposited by sputtering from targets composed of 2-4% Al metal incorporated in ZnO
Electrical conductance, measured as bulk resistivity or as sheet resistance, related to deposition properties and thickness
5Source: http://materion.com/ResourceCenter/ProductData/InorganicChemicals/Oxides/AZOTransparentConductiveCoating.aspx
CONDUCTIVE LAYER: AZO
Full range of sheet resistance, from < 50 Ω/sq to M Ω/sq, can be obtained with AZO by varying deposition thickness and parameters
No substrate heat is required. Patterning of films by etching is easier than with ITO films. Weak acids of <1% concentration (0.2% HNO3 for 2 minutes at 18° C) can be used
The refractive indices for reactive magnetron sputtered AZO at 600 nm wavelength range from 1.90 ± 0.02. Pulsed DC magnetron sputter deposition of AZO produces an index ~2.00
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CONDUCTIVE LAYER: AZO
Property of high transmission in the visible region and useable transmission to IR wavelengths as long as ~12 μm.
In contrast, the more commonly known TCO,
ITO, reflects IR at wavelengths longer than ~2 μm.
Transmittance loss for a 120 nm thick coating on Ge is <10% out to ~12 μm.
7
METHODOLOGY: LITERATURE REVIEW
Preparation and characterization of ZnO thin films deposited by sol-gel spin coating method
Thickness changes inversely with increasing or decreasing chuck rotation
Effect of Sol Concentration on Structural and Optical Behavior of ZnO Thin Films Prepared by Sol-Gel Spin Coating
Grain size increases with increase in molar concentration of the deposited thin films 8
METHODOLOGY:LITERATURE REVIEW
Al-doped ZnO via Sol-Gel Spin-coating as a Transparent Conducting Thin Film
Crystallite size increases but Electrical resistivity decreases with increasing Al concentration
Structural and optical properties of ZnO: Al films prepared by the sol–gel method
Increasing Al concentration leads to an amorphous stage of the film appears higher than 2 wt.% of concentration
9
METHODOLOGY:LITERATURE REVIEW
Damp heat stability of AZO transparent electrode and influence of thin metal film for enhancing the stability
Mobility decreased with increasing Al concentration
Low Temperature Sol-Gel Technique For Processing Al-Doped Zinc Oxide Films
Each annealing concentration of oxygen increased and concentration of carbon decreased in the films
10
AZO PREPARATION: SOL-GEL METHOD
Method for producing solid materials from small molecules
Conversion of monomers:
A colloidal solution (sol) that acts as the precursor for an integrated network Gel of either discrete particles or network polymers
Sol (or solution) evolves gradually towards the formation of a gel-like network containing both a liquid phase and a solid phase
11
AZO PREPARATION: SOL-GEL METHOD
Sol-gel Method steps:
HydrolysisCondensationGelationAgeingDryingDensification
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AZO PREPARATION: SOL-GEL METHOD
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AZO PREPARATION STEPS
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EXPERIMENTAL LAYER PREPARATION
Glass Substrate: 1’’×1’’Sample Slide Cleaning: Ultrasonic Bath
(USB) process Cleaned by brush with de-ionized water and
washed by methanol as mechanical scrubbing- Methanol for 10mins- Acetone for 10mins- Methanol for 10mins-De-ionized Water for 10mins
15
EXPERIMENTAL LAYER PREPARATION
AZO Solution Preparation
Magnetic Stirring of the Solution: - 2hour at 60 degree Celsius - Solution was allowed to aged for 24 hr in room temperature
Elements Role
Amount
Zinc acetate dehydrate [Zn(CH3COO)2. 2H2O]
Starting Materia
l5.39g
2-methoxy ethanol (CH3OCH2CH2OH) Solvent 46.93g
Mono-ethanol-amine [(HOCH2CH2)NH2]Stabiliz
er 1.5ml
Aluminum nitrate nonahydrate [Al2(NO3)3.9H2O]
Doping Materia
l0.11g
16
EXPERIMENTAL LAYER PREPARATION
Deposition & Spin Coating of the Sample Slides
-Solution: 0.5 ml
- RPM: 3000
- Spin Time: 30 seconds
- Rotation/Sec2: 500
17
EXPERIMENTAL LAYER PREPARATION
Ageing using Oven
- At 300 degree Celsius - Cycle was done for 5, 10 & 15 times
- Kept in Oven for 10mins
18
EXPERIMENTAL LAYER PREPARATION
Drying in Ambient Temperature
- Pre-heating stability gain
- At room temperature - for 10mins for all
substrates Annealing for
Densification
- Both Air & Vacuum annealing
- Nitrogen purging for Air annealingat 500 Degree Celsius
- Vacuum annealing for 1 hour
19
EXPERIMENTAL LAYER PREPARATION
Preparation Completion
- Kept for 24 hours for making samples stable
- AZO substrates are ready for experiment
20
AZO CHARACTERIZATION
Thickness Measurement
- layer thickness influence the efficiency- Being too thin affect efficiency and durability, being too
thick can increase cost- Profilometer is used to measure the surface thickness
Surface Morphology Test
- Analytical Imaging test- Test is performed for detecting surface defect and
roughness- Surface Imaging Information: Surface structures & defects
21
AZO CHARACTERIZATION
Hall Effect Measurement
- Production of a voltage across an electrical conductor, transverse to an electric current in the conductor and a magnetic field perpendicular to the current
- Determining resistivity & conductivity
22
THICKNESSMEASUREMENT
Testing Preparation Wet Etching Process- Using masking tap in one side- Weak solution of HNO3
HNO3 Solution Preparation
- 125ml of De-Ionized (DI) water in beaker - 0.32ml of HNO3 poured in it - De-Ionized water upto 500ml
23
THICKNESSMEASUREMENT
Etching the Substrates
- Kept substrates drenched 10mins in solution- Taken up and rinsed by De-Ionized
water, then dried 10mins- Removed mask and got side etch
24
THICKNESSMEASUREMENT
Testing
- Stylus Surface Profilometer, Model: Detak-150 was used
- Layer: 1, 10 & 20 timesAZO solution deposited
25
THICKNESSMEASUREMENT
Result
- For 1-layer: 504nm - For 10-layer: 5851.9nm - For 20-layer: 10311.8nm
Observation
- Huge improvement in layer thickness with each deposition- Each deposition obtained significant improvement
in layer thickness hence increase performance
26
THICKNESSMEASUREMENT
Observation
1-layer 10-layer 20-layer0
2000
4000
6000
8000
10000
12000
Layer Thickness
Layer
Thic
knes
s (µ
m)
Improvement trend of layer thickness with deposition
27
SURFACE MORPHOLOGYTEST
Testing
- Used Stylus Surface Profilometer, Model: Detak-150- Observe the surface roughness of the
substrates in particular its adhesion, microstructure and final topography
28
SURFACE MORPHOLOGYTEST
Result
The layer roughness are:
For 1-layer, Ra: 45.3nmFor 10-layer, Ra: 11545.1nmFor 20-layer, Ra: 1885.1nm
29
SURFACE MORPHOLOGYTEST
Observation
Roughness of surface increased by the number of layer
1-deposition the roughness is futile; doesn’t affect the surface (grain size) at all
From 1-times to 10-times roughness increases highly
From 10-times to 20-times not significantly Increasing of doping concentration doesn’t
increase the smoothness after certain layer deposition
30
HALL EFFECTMEASUREMENT
Testing
10 times deposited layer Instrument: ECOPIA HMS-3000
31
HALL EFFECTMEASUREMENT
Result
Bulk Concentration: -9.675×1010 /cm3 Mobility: 1.564×103 cm3/VS Resistivity: 4.126×104 Ω-cm Magneto-Resistance: 2.698×108 Ω Sheet Concentration: -6.627×106/cm2 Conductivity: 2.423×10-5/ Ω-cm Average Hall Coefficient: -6.452×107cm3/C
32
HALL EFFECTMEASUREMENT
I-V Curve
33
HALL EFFECTMEASUREMENT
Observation
Hall Coefficient value was measured as -6.452×107cm3/C
Negative sign of the Hall coefficient indicates Al-doped ZnO are n-type
Conductivity is 2.423×10-5/ Ω-cm means the substrates has optimized conductivity
After Vacuum Annealing the resistivity is 4.126×104 Ω-cm
Indicates post-heat-treatment in a reducing environment efficiently reduced the electrical resistivity, affected mainly the oxygen vacancy concentration
34
Increasing efficiency of Al doped ZnO will increase efficiency of Thin film
Need to endeavor:
- Impact of layer deposition on roughness - Impact of conductivity increase at annealing
temperature variation - Optimize high efficient grain size doping (i. e.)
material and chemical composition
FUTURE WORK SCOPE
35
Thank You
Q/A