Transcript Final Presentation

JESUS GUARDADO, LEAH NATION, HUY NGUYEN, TINA RO
The Effect of Carbon Nanotubes in
Polymer Photovoltaic Cells
May 13, 2010
Agenda
• Overview of Market
• Goal of Project
• Science & Design of Cell
• Fabrication Procedures
• Results
• Analysis
• Future Work
Current Market Projection for Photovoltaics
•Investments on the rise
•Photovoltatic capacity is
increasing
•Avg growth rate >40%
for past 5 years
Our Focus: Polymer Photovoltaic Cells (PPC)
Increased market focus on
diversifying solar technologies
Potential fabrication advantages
• Low processing temperature
• Printable
Unique application possibilities
• Light weight
• Flexible
Current disadvantages
• Lifetime instability
• Lower efficiency
Polymer Photovoltaic Cell Efficiency Growth
24.7%
20.3%
Crystalline Si Cells
(Single and Multi-crystalline)
Thin-Film Technologies
(Amorphous Si:H)
Organic Photovoltaics
12.1%
5.4%
Project Goals
•Add carbon nanotubes (CNTs) to increase cell photovoltaic
response
•Make functional cells to validate photoresponse mechanism
•Match current polymer photovoltaic cell (PPC) cell efficiency
Focus: sw-CNTs
SWCNT at 80,000x
Single-walled carbon nanotubes
• Large surface area
• High e- affinity
Aids cells
• Improve carrier transport
• Induces crystallinity
Cost: +$8 per m2
Cell Design
Based on past research
Cell parts:
• Active layer (with CNTs)
• Charge acceptors
• Electrodes
FTO – Fluoride Tin Oxide
How It Works:
Photons => Exitons
Carbon Nanotubes:
•Charge transport
•Facilitate disassociation
How It Works:
Electron => TiO2
Hole => PEDOT
How It Works:
Electrodes accept charges
Procedures
Prepare Solutions
Fabricate Samples
Test Samples
Preparing the Solutions
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Mix P3HT and solvent
Add varying conc. of CNTs
CNTs => main variable
Sonicate & centrifuge to debundle CNTs
Evolution of the solutions
Variable
Round 1
Round 2
Why?
mg P3HT/mL Solvent 4:1
10:1
Thicker P3HT Layer
Better heterojunctions
CNT
1 & 2 wt%
Compare conc.
Emulate previous studies
3.7 & 6 wt%
Device Fabrication
Prepare substrate
• Clean FTO substrate
• Separate layers with tape
Spin Coat
• Must optimize rpm
• 800 rpm for thick layers
• 1200 rpm for thin layers
Deposit top electrode
• Thermal vapor deposition
Taping pix here
Fabricated Cell
Tests
UV-Vis on solutions
• Confirms semiconductor properties
Open circuit voltage
• No light vs desk lamp
• Tests for photoresponse
IV-Curve
• Determines cell performance
UV-Vis Spectroscopy
•samples with CNTs
show increased photoresponse compared to
control cells
•absorption increases
as the wt% CNTs
increases
CNT Concentration vs. Voc Trend
I-V Curves
Observed Behavior Desired Behavior
•Resistors
•Diode
•Short circuit
IV Curves: Round I
Typical IV curve of our
samples
•The symmetry about the
0V axis implies there is
no bias in electron/hole
travel
Sample 4, Concentration 1
Fabrication: 4/6
Testing: 4/14, 4/27
IV Curve: Round II
Verified
Expectations
Summary
CNTs: with increasing wt %
• Visible and IR Absorption increased
• Voc increased
Sources of
Error
Fabrication Variables
• Inter-layer penetration yielded short circuits
• Human imprecision
Testing Variables
• Delay between fabrication and testing
resulted in degraded samples
• Oxidation of materials
Geng, J.; Zeng, T. Journal of the American Chemical Society 2006, 128,
16827-16833.
Future Work
Materials
• Investigate the effects of the TiO2 layer
• Study alternative materials to P3HT
• Explore different materials for the heterostructure’s
layers
Fabrication & Testing
• Experiment with the engineering parameters
for fabrication
• Standardize testing
Acknowledgements
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•
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Helen Zeng
Yin-lin Xie
Jill Rowehl
Prof. Yet-Ming Chiang
3.042 – Materials Project Laboratory
Staff
Facilities:
•
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Institute of Soldier Nanotechnologies
(ISN)
Organic Nanostructure Electronics (ONE)
Lab
Thank you.
Questions?
You may reach us at [email protected]
http://web.mit.edu/course/3/3.042/team1_10
Appendix
Renewable Energy Comparison
Current Progress & Future Schedule
Cost Estimation
$/gram
mg/mL L/slide slides/meter $/meter
100 0.1875 0.0001
4444.44
8.33
PRODUCTION COSTS, to be added to
other company's approximation of $/meter
CNT $
15-20% cnts
Profilometry: Ag/TiO2 Border Image
Silver
TiO2
Profilometry: Active Layer/PEDOT Image
ACTIVE
LAYER
PEDOT