Solar Energy
Daniel A. Higgins
QuickTime™ and a
Dept. ofTIFF
Chemistry,
Kansas
State University
(Uncompressed)
decompressor
are needed to see this picture.
Energy, Environmental Impacts, and
Sustainability
Intersession Workshop
Solar Electric
Solar Energy
Wind Energy
Wave Power
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Ocean Power Delivery, Ltd.
Hydroelectric
Quic kTime™ and a
TIFF (Unc ompres sed) dec ompres sor
are needed to see this pic ture.
Petroleum
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Babcock/NREL
Coal
Natural
Gas
ACS
“Convenient” Access to Solar Energy
• Coal, Petroleum, Natural Gas
– Coal: ≈ 20 MJ/kg
– Petroleum: ≈ 48 MJ/kg
– Natural Gas: ≈ 59 MJ/kg
• Problem:
– It Takes Millions of Years to Form Fossil Fuels
– Equivalent ≈ 8x109 metric tons of
Petroleum/year
– 5.4x109 metric tons Carbon Emitted/year
– NOT Sustainable!
How Much Solar Energy?
• Energy used by Earth’s Inhabitants:
– 400 EJ in ONE YEAR
• Energy from the Sun:
1 EJ = 1x1018 J
– 10,800 EJ in ONE DAY
– 27X More than Used in One Year
• Photon Energy
– in Visible:
– 240 kJ/mole
– 2.5 eV
Direct Solar
• Passive Solar
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
– Greenhouse Effect
• Active Solar
– Solar Thermal
• Concentrate, Heat from Sun
– Solar Electric
• Photovoltaics
• Sunlight --> Electricity
Aitken/NREL
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
SES/Boeing/NREL
PowerLight/NREL
• In kWh/kW-yr
Solar - Where?
From: NREL
To Meet All Our Needs: Solar Area = 100x100 miles2
Photovoltaic Cells
• Mostly Silicon
• Crystalline, Microcrystalline, Amorphous, Thin Film
From: Ken Zweibel, NREL
Photovoltaic Efficiency (Solar)
Limited by Photon Energy, Band Gap
E
I mp Vmp
Pin

QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
http://www.solarserver.de
Component/Cost Issues
• Solar Photovoltaics
– ≈ $3-4/Wp
– ≈ $0.15-$0.30/kWh
• Biggest Factor– PV Module
– Materials/Efficiency
• Challenge:
• Large Area PVs
• CHEAP!
First Solar Thin-Film PV Module
System Costs
100.00
History
All Power Modules – Accel.& Bus.as Usual
Large Modules – Accelerated
Large Modules – Bus. As Usual
60.74
Forecast
NREL
Power Modules
Average Selling Price
20.79
$/Wp
History
10.67
10.00
7.60
8.17
5.65
5.94
4.80
3.65
3.80
Large Modules
Sold in Quantity
2.892.74
2.111.78
2.662.52
2.001.69
1.00
1975
1980
1985
1990
1995
2000
2005
2010
03489805a
Photovoltaic Production
MW
1200
1150
1100
1050
1000
950
900
850
800
750
700
650
600
550
500
450
400
350
300
250
200
150
100
50
2003
2002
2001
2000
1999
1998
1997
1996
1995
1994
1993
1992
1991
1990
1989
1988
From NREL - Derived from PV News
World
US
Japan
Europe
Other
Reducing Cost - Emerging Materials
• Organic Semiconductors
–
–
–
–
Semiconducting Polymers
Small Molecule Organics
Dye-Sensitized
Composite Devices
Like Thin-Film Inorganics
• Advantages
– Coat Arbitrary Surfaces
– Photovoltaic “Paint”?
– Less Expensive Materials
• Challenges
Ken Zweibel, NREL
– Less Efficient
– Different Mechanism (Tightly Bound Excitons)
New Photoactive Organic Films - KSU
• Previously:
– Symmetric Diimides
– Crystalline or Liquid Crystalline (at High Temperatures)
– Polymer-Diimide Composite Films
O
R
N
O
• Optoelectronic Properties: From Chromophore
• Mechanical/Morphological(?) Properties: From Polymer
• Our Proposal:
– Asymmetric Water Soluble Diimides
– Polyelectrolyte-Surfactant Composites - as Thin Films
•
•
•
•
Optoelectronic Properties: From Perylene Diimides
Mechanical Properties: From Polymer + Surfactant
Solution Processible - Casting from AQUEOUS Solutions!
Self-Assembled Lamellar Phases - “Self Healing”
O
N
R'
O
Compounds Synthesized - KSU
C12
-PDI+
O
N(CH3)3 +
N
O
N(CH3)3 +
O
N
O
N(CH3)3+
C11O-PDI+
O
N
O
PDI2+
Increased
Solubility
O
N
O
O
N
O
O
O
N
O
N(CH3)3+
Credits: Sarah Barron, Amy Twite,
Jeff Hall, Duy Hua
C12-PDI+/PA- Thin Film Structure SAXS
More Complex Structure Present?
Polymorph?
Angstrom Scale
Disorder
Bilayer Spacing:
3.9 nm
Xie, Liu, Hall, Barron and Higgins, Langmuir, 2005, 21, 4149.
p-n Heterojunction Devices
metal
C12-PDI+/PATPD
ITO
Glass
I or V
Current (nAmps)
C12-PDI+/PA- Devices
150
100
50
0
-2
0
2
Voltage (Volts)
4
0.6 W/cm2 at 488 nm
Photovoltage (mV)
Present Characteristics:
< 200 mV Photovoltage
Nanoamp Photocurrents
Long Rise/Decay
Due to:
High Series Resistance
200 Max PV = 171 mV
150
Decay = 67, 710 s
100
50
Rise = 4.6, 56 s
0
0
400
800
Time (s)
1200
1600
MP Fluorescence - PDI Films
Low Loading (≈ 2% C12-PDI+ in PA-)
Log(Fluorescence)
Two Photon Excitation of PDI
3.6
Slope = 1.8
3.2
2.8
2.4
-0.6
-0.4
-0.2
0.0
Log(Power(mW))
300 µW Incident
Broad Emission Spectra
Monomer and CT Exciton Emission
Heterogeneous
Polarization Dependent MP Excitation
– Nanometer Scale Organization
• C12-PDI+/PA- Composites
Ordered?
3cos 2  1
s
2
– Order Parameter:
• Measure 0.09
• 1.0 = Perfect Order

• 0.0 = Random
Organization
Xie, Liu, Hall, Barron and Higgins, Langmuir, 2005, 21, 4149.
MP Polarization Dependence
Stoichiometric PDI2+/PA-
Ordered Fibers
And
Polarized Excitation
Fiber Axis
Summary and Future Directions
New Organic Photovoltaics
 Today:
 Silicon, Others: Crystalline, Amorphous, Films Viable
 Costs Still High
 Materials Costs Reductions Possible with Organics
 At KSU:
 Perylene Diimide Polyelectolyte Composites
 Prepared from Aqueous Solutions
 Future:
 Energy Storage an Issue
 Improvements in Thin Film Characteristics
 Development of Simple Coating Procedures
 Increased Emphasis Needed at National Level
PDI2+/PA- Fluorescence
No PA-
Stoichiometric
Complex
C12-PDI+/PA- and PDI2+/PA- Aggregation
Emission
4
2
Fluorescence
0
12
8
4
0
PE/C12-PDI+
0
1.5
CT
1.1 Exciton
40x10 -3
PE/PDI2+
30
0
20
0.9
10
1.9
0
600 650 700 750 800 850 2.8
3.7
4.7
Wavelength (nm)
550
600
650
Wavelength (nm)
700
750
Frenkel
Exciton
Excitation
CT
Exciton
1.0
Fluorescence
In Water
Fluor
Fluorescence
6
0.8
0.6
PE
1.9
PE
0
0.4
0.2
0.0
400 450 500 550 600
Excitation (nm)
CT Exciton:
Weak Emission (f < 0.01)
Xie, Liu, Hall, Barron and Higgins, Langmuir, 2005, 21, 4149.
Multiphoton Microscopy
Glass
Substrat
Sample
Sample-Scanning
Confocal Microscope
• High Resolution
Imaging
Sample
Piezoelectric
Scanning Stage
(Closed Loop in X,Y)
• Low Background
• Depth Discrimination
ExcitationLaser
Light
From Ti:Sapphire
(Ti:sapphire)
810 nm
80 MHz
170 fsec

Scanning
Microscope
Stage
Objective
Objective
n
Pfl  Iinc
Beam Splitter
Pfl  I() n
To Detector
Spectrograph/CCD
APD/PMT