3.003 Principles of Engineering
E
Practice
Silicon Solar Cell Design
g and
Man
nufacturing Plan
Stude
ent B
Team SoloLoco
3.003 Principles of Engineering
E
Practice
Dev
vice Schematic
• Surface area = 100
cm^2
• Texture =
.1(thickness)
• Doping: 1x10^16
cm^-3
• ARC thi
thickness
k
=
(500 nm)/4
(Not to scale)
• ARC refractive index
= (n1n2)^.5 = 2
• Efficiency = 15.21%
3.003 Principles of Engineering
E
Practice
PC1D
D Simulator and
Assu
umptions Made
• Most parameters remain
n at their default value
• Texture,
Te t re AR ccoating
oating add
ded
• Thickness reduced to 30 um – “thick film”
• First front diffusion doping changed to 1x10^19 cm^-3
peak to make p-n junctio
on
• E
Excitation
it ti from
f
ONE-SU
ONE SU
UN averages iincident
id t power
from the sun on a clear day
• Limited by DC current fflow from solar panels
• Limited by lack of energ
gy storage technique/device
3.003 Principles of Engineering
E
Practice
Tradeoffs
• Film thickness vs. lifetim
me
• Lifetime – lifetime of indiv
vidual carrier when struck by
y sun
• Carrier diffusion length – average distance carrier travels in its
lifetime
• Carrier
C i diff
diffusion
i length
l
th = (carrier
(
i diff
diffusivity
i it * lif
lifetime)^1/2
ti )^1/2
m
be greater than thickness of cell
• Carrier diffusion length must
• Thicker cells (i.e.
(i e wafers)) run the risk of not being useful if
thickness > carrier diffusiion length
• Cost
• Wafers vs. thick films vs. thin films
y to manufacture but fare better in
• Thin films are most costly
original tradeoff
3.003 Principles of Engineering
E
Practice
1.
Manufacturing
Processes
Silicon extracted and purifie
ed
2. Silicon is p-type doped (bac
ckground doping)
3. Texturing added
4. N-type doping added to ma
ake p-n junction
5. Anti-reflective coating adde
ed
6. Metal contacts added to “co
ollect” current
7. Final cell assembled
•
Cell is tested and purified mu
ultiple times throughout this process
•
Manufacturing costs are the thing that most affects difference in
price between different kinds
s of cells
•
Manufacturing process will o
originally rely on fossil fuels but will
eventually rely completely on
n solar power
3.003 Principles of Engineering
E
Practice
Projected Cap
pability of Production
an
nd Recommendations
• Solar cell factories can be operational within 18
months of project appro
oval and run at full capacity after
another
th year
• A mature 430 MW solarr cell factory produces about
200 million cells/year an
nd creates about 300 jobs
• We must implement ma
anufacturing process slowly to
a o for
allow
o improvements
p o e e ts in technology
tec o ogy and
a d increased
c eased
support of project
• We must invest in resea
arch for converting DC current
to AC and for solar enerrgy storage techniques
• In the meantime, we mu
ust invest in DC household
appliances
li
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3.003 Principles of Engineering Practice
Spring 2010
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