Nanomaker
Lab$#11:$Silicon$Photovoltaics$(PV)$
Photograph and illustration of BigBelly smart trash can removed
due to copyright restrictions.
1
Solar Energy
Fabrication
Material Defect
Efficiency
2
Solar Energy
SUN%
EARTH%
D%(Distance%to%Sun)%
Rsun%
Total%radia:ve%power%of%sun%
(Stefan>Boltzmann%law,%T=5762±50K)%
Psun
Radia:ve%power%of%
sun%per%unit%area%
(5.961x107%W/m2)%
⇥T 4
=
2
4πRsun
Surface%area%of%Sun%
Ra:o%of%
surface%area%
Pearth
2
Rsun
=
Psun
2
D
Average%power%
(1366%W/m2)%
3
Solar Spectrum
(1366%W/m2)%
(1000%W/m2)%
Image created by Robert A. Rohde / Global Warming Art. Used with permission.
Nearly%~50%%of%the%solar%irradiance%is%in%the%visible%spectrum%%
Lots%of%solar%power%is%in%the%form%of%IR%light%
4
Atmospheric Effects
Atmospheric%effects%have%several%impacts%on%
the%solar%radia:on%at%the%Earth's%surface.%The%
major%effects%for%photovoltaic%applica:ons%are:%
•%A%reduc:on%in%the%power%of%the%solar%
radia:on%due%to%absorp:on,%sca_ering%and%
reflec:on%in%the%atmosphere;%
•%A%change%in%the%spectral%content%of%the%solar%
radia:on%due%to%greater%absorp:on%or%
sca_ering%of%some%wavelengths;%
•%The%introduc:on%of%a%diffuse%or%indirect%
component%into%the%solar%radia:on;%and%
•%Local%varia:ons%in%the%atmosphere(such%as%
water%vapor,%clouds%and%pollu:on)%which%have%
addi:onal%effects%on%the%incident%power,%
spectrum%and%direc:onality%
Courtesy of PVCDROM, Christiana Honsberg
and Stuart Bowden. Used with permission.
5
Insolation
Insola:on:%Incoming%Solar%Radia:on%
Energy'per'Unit'Area'per'Unit'Time'(kWh/m2/day)%
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6
Solar Energy
Fabrication
Material Defect
Efficiency
7
Silicon Crystal Growth
Single%Crystal%Si%Boule%
Silicon%Wafers%
Both images are in the public domain.
Czochralski%growth%
This image is in the public domain.
Polycrystalline%Silicon%Solar%Cell%
This image is in the public domain.
Ribbon%growth%
© source unknown. All rights reserved. This content is excluded from our Creative
Commons license. For more information, see http://ocw.mit.edu/fairuse.
8
Silicon Crystal
Grain
boundary
Each silicon atom is bonded
to four neighbouring atoms.
Image by MIT OpenCourseWare.
Width$
(cm)$
Growth$rate$
(mm/min)$
Throughput$
(m2/day)$
Energy$use$
(kWh/m2)$
Best$
efficiency$
Czochralski$
15%
0.6%>%1.2%
30%
21%>%48%
20%%
Ribbon$Silicon$
8>80%
15%>%20%
20%
20%
18%%
9
Why Purple?
70
60
Reflectance (%)
50
40
30
20
10
400
500
600
700
800
900
1000
1100
This image is in the public domain.
Wavelength (nanometer)
Before ARC
After ARC
Image by MIT OpenCourseWare.
Reflectance%curve%of%a%polycrystallinesilicon%solar%
cells%before%and%ager%silicon%nitride%coa:ng%
10
Low-Cost: Roll-to-Roll Vacuum Coating
Photographs of the vaccuum coating process removed due to copyright restrictions.
Amorphous$Silicon$Solar$Cell$
Nine%miles%of%solar%cells%in%three%days%%
Photo courtesy of US Army Africa on Flickr.
11
Solar Energy
Fabrication
Material Defect
Efficiency
12
Polycrystalline Silicon
This image is in the public domain.
Metal%Impuri:es%
Disloca:ons%
Edge,%Screw,%Mixed,%Loops%
%
Iron, Titanium, Nickel,
Chromium, Copper
%
Non>Metal%Impuri:es%
Grain%boundaries%
Small>angle,%Large>angle%
%
%
Oxygen, Nitrogen
Carbon
%
250m
Courtesy of Tonio Buonassisi. Used with permission.
Adopted%from%Prof.%Buonassisi%%
13
High Quality Materials
"$
%"
'!
%
"$
%"
!!
!%
!))
+!!,'
Adopted%from%Prof.%Buonassisi%%
Courtesy of Tonio Buonassisi. Used with permission.
14
Low Quality Materials
"
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+ $-"%(-
$*
""
/ "0($
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"%*
"
#
!
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#)*.
#&((&!
&!
!!!/(
Adopted%from%Prof.%Buonassisi%%
Courtesy of Tonio Buonassisi. Used with permission.
15
"%
(1)%
"%
(2)%
#
#
'!$
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) -!&
# %
& ,
++)++)+#+)
+)')657665175592+
"%
(3)%
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(4)%
#
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(%
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./*
**(**
"*#(
*)((344325.4228/*
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Adopted%from%Prof.%Buonassisi%%
Courtesy of Tonio Buonassisi. Used with permission.
16
Lock-in Thermography
Courtesy of Elsevier, Inc., http://www.sciencedirect.com. Used with permission.
DC%
Lock>in%
#  Ribbon>Si%Device%
#  100%Hz%lock>in%frequency%
#  0.6%V%bias%
17
Solar Energy
Fabrication
Material Defect
Efficiency
18
IV Characterization
h
p-type
eV
Ec
h
Ev
Load R
IL:%excita:on%due%to%photon%short%
circuit%current%
Courtesy of Tonio Buonassisi. Used with permission.
19
Efficiency
MPP:$Maximum$Power$Point$
Quadrant$flipped!%
Adopted%from%Prof.%Buonassisi%%
Courtesy of Tonio Buonassisi. Used with permission.
20
Adopted%from%Prof.%Buonassisi%%
Courtesy of Tonio Buonassisi. Used with permission.
21
Conclusions
Single%Crystal%
Polycrystalline%
Crystal%
1%Sun%=%(1000%W/m2)%
This image is in the public domain.
Image created by Robert A. Rohde / Global Warming Art. Used with permission.
Metal Iimpurities
Metal mpuri:es Iron, Titanium, Nickel,
Iron, Titanium, Nickel Chromium,
Copper
Chromium, Copper Non-metals
Non-­‐Metal Impuri:es Oxygen, Nitrogen
Oxygen, N
Carbonitrogen Carbon Dislocations
Disloca:ons This image is in the public domain.
250m
Edge, Screw,
Edge, Screw, Mixed, %
Mixed,
Loops...
Loops Grain
Grain boundaries
boundaries CSL, Small-angle,
Small-­‐angle, Large-angleLarge-­‐
angle %
Courtesy of Tonio Buonassisi. Used with permission.
22
MIT OpenCourseWare
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6.S079 Nanomaker
Spring 2013
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