Solar Cells: When will they BecomeEconomically Feasible?

6th Session of MT5009

A/Prof Jeffrey FunkDivision of Engineering and Technology Management

National University of Singapore

For information on other technologies, see http://www.slideshare.net/Funk98/presentations

Objectives

What are the important dimensions of performance for solar cells and their higher level systems?

What are the rates of improvement? What drives these rapid rates of

improvement? Will these improvements continue? What kinds of new systems will likely

emerge from the improvements in solar cells?

What does this tell us about the future?

Session Technology

1 Objectives and overview of course

2 Two types of improvements: 1) Creating materials that better exploit physical phenomena; 2) Geometrical scaling

4 Semiconductors, ICs, electronic systems

5 MEMS and Bio-electronic ICs

6 Nanotechnology and DNA sequencing

7 Superconductivity and solar cells

8 Lighting and Displays

9 Human-computer interfaces (also roll-to roll printing)

10 Telecommunications and Internet

11 3D printing and energy storage

This is Part of the Seventh Session of MT5009

Creating materials (and their associated processes) that better exploit physical phenomenon

Geometrical scaling◦ Increases in scale◦ Reductions in scale

Some technologies directly experience improvements while others indirectly experience them through improvements in “components”

As Noted in Previous Session, Two main mechanisms for improvements

A summary of these ideas can be found in 1) forthcoming paper in California Management Review, What

Drives Exponential Improvements?2) book from Stanford University Press, Technology Change and

the Rise of New Industries

Creating materials (and their associated processes) that better exploit physical phenomenon◦ Create materials that better exploit phenomenon of

photovoltaic◦ Create processes that enable these materials to better exploit

phenomenon of photovoltaic Geometrical scaling

◦ Increases in scale: larger substrates and production equipment lead to lower cost in much the same way that cost of LCDs and other displays have fallen (see other sessions for more details)

Some technologies directly experience improvements while others indirectly experience them through improvements in “components” ◦ Better solar cells lead to better modules and new ways of

organizing electricity production

Both are Relevant to Solar Cells

http://www.economist.com/news/21566414-alternative-energy-will-no-longer-be-alternative-sunny-uplands

Solar cells are getting cheaper…………Partly because they are becoming more efficient

Why does this slide make meoptimistic about solar?

But a Long Way to Go

Coal-fired power plants $2.10 a watt Large hydroelectric systems can be cheaper

◦ Three Gorges Dam was supposedly about $1 a watt◦ But actual costs are widely believed to be much higher

Natural gas-fired peaking power plants -$6 a watt Large wind turbines -$2 a watt – but low capacity

utilization (27%) Solar panels currently selling for as low as US$0.70

a watt in large quantities◦ But installation costs are $2-4$ per watt◦ And capacity utilization is very low (18%)

Except for peaking plants (see next slide), we need much lower module and installation costs

http://en.wikipedia.org/wiki/Price_per_watt; http://thebreakthrough.org/index.php/programs/energy-and-climate/how-fast-are-the-costs-of-solar-really-coming-down/

Electricity Usage by Time of Day in Florida

How do solar cells work? Improvements in cost of electricity from solar cells

Improvements in Efficiency Multi-junction cells

Improvements in cost per area Increases in scale Reductions in thicknesses

Conclusions

Outline

Photovoltaic systemsSolar Cells in a Utility or on a Building

Thermal Energy SystemsVery Different from Solar Thermal Systems

Solar Cells Produce Electricity Based on Photovoltaic Effect

1839: First recognized by the French physicist Alexandre-Edmond Becquerel

1883: First solar cell constructed from selenium by Charles Fritts

1946: modern junction semiconductor solar cell was first patented in 1946 by Russell Ohl

1954: first silicon solar cell was constructed by Calvin Fuller, Daryl Chapin, and Gerald Pearson

Subsequently other materials have been found some as recent as 10-15 years ago

Brief History of Photovoltaic Effect

Semiconductor materials were found to exhibit the photovoltaic effect in the 1950s, 60s and 70s◦ Silicon, including single crystalline, polycrystalline, and

amorphous silicon◦ Cadmium Telluride (CdTe)◦ Copper indium gallium selenide (CIGS)◦ Gallium arsenide

But also non-semiconductor materials, which were more recently found◦ Photo-sensitive dyes (titanium oxide)◦ Some organic materials◦ Some of these materials can be used to make quantum dots or

have Perovskite crystals

Materials that Exhibit Photovoltaic Effect

Incoming solar radiation creates “electron-hole” pairs in material These electrons and holes create electricity when they reach opposite

terminals of device Only photons whose energy exceeds band-gap of material create

electron-hole pairs◦ Other photons do not create electron-hole pairs

◦ Energy greater than this band gap is lost

There has been a search for materials that ◦ exhibit photovoltaic effect

◦ have appropriate band gap

◦ have little recombination of electrons and holes

◦ are inexpensive to acquire and process

Within a type of solar cell, there has been a search for the

appropriate combination of material and process specifications

Looking at Photovoltaic Effect in more Detail

Conductionband Band gap

Valenceband

Materials with higher band gaps increase the amount of energy from each absorbed photon◦ but reduce the percentage of incoming radiation that

can be transformed into electrons and holes. Thus, there is a tradeoff between low and high

band gaps Given the distribution of the solar spectrum

◦ the optimal band gap in terms of efficiency can be calculated

◦ the maximum theoretical efficiencies can be calculated (about 30%)

◦ Many materials have a maximum theoretical efficiency of about 30%

What is the Best Band Gap?

Examples of Efficiency Losses

Reflection of photons by glass.Absorption of photons by glass (heat)

Recombination of electron hole pairs before reaching terminals(crystalline materials have less recombination)

Photons pass through material without generating electron-hole pairs

But even if the best band-gap is used, there will be losses

One way to overcome limitations of individual materials is to use multiple junctions◦ Each has band gap that is appropriate for different part

of solar spectrum These solar cells can have

◦ much higher efficiencies than single junction ones◦ but they also have higher costs as multiple layers must

be deposited, patterned and etched One way to reduce costs is to

◦ focus sunlight onto multi-junction cells using concentrators

◦ but concentrating mirrors require mechanical and electronic controls, gears and other potentially unreliable components

More on this later

Multiple Junctions

How do solar cells work? Improvements in cost of electricity from solar cells

Improvements in Efficiency Multi-junction cells

Improvements in cost per area Increases in scale Reductions in thicknesses

Conclusions

Outline

Depends on a lot of factors but to simplify….

Cost of electricity depends on ◦ amount of incoming solar radiation◦ cost per “Peak Watt” of a module (based on a

predetermined amount of incoming solar radiation)

◦ cost of installation including cost of capital, land, labor, etc.: becomes more important as cost of “modules” drop

Cost per “Peak Watt” depends on ◦ cost per area of solar cells◦ efficiency of solar cells

Cost of Electricity

Amount of incoming solar radiation

world electricity demand

(18,000 TWh/y)

can be produced from

300 x 300 km²

=0.23% of all deserts

distributed over “10 000” sites

3000 km

Sources: Gerhard Knies, CSP 2008 Barcelonaand Vinod Khosla 25

deserts as solar farms

Improvementsin what technology might make this economically feasible?

Source: WikipediaDesertec

Source: Physica C: Superconductivity Volume 484, 15 January 2013, Pages 1–5. Proceedings of the 24th International Symposium on Superconductivity (ISS2011). CIGRÉ SC D1 WG38 Workshop on High Temperature Superconductors (HTS) for Utility Applications Beijing, China, 26 April 2013

Can these improvements make solar economical for Europe?

Now

2 years

4 years

What About Cost Per Peak Watt of Modules?Depends on cost per area and Efficiency

Cost per area

($/m2) 50 100 200

Costper Area

200

100 50

0 2 4 6 8 10 12 14 16 18 20 22

Cos

t ($)

per

Pea

k W

att

1.5

1

.5

0

Efficiency

Improvements in either Cost per area or Efficiency can lead to a Lower Cost per Peak Watt

Cost per area ($ per square meter)

50 100 200

Costper Area

200

100 50

0 2 4 6 8 10 12 14 16 18 20 22

Cos

t ($)

per

Pea

k W

att

1.5

1

.5

0

Efficiency

Improvements in Improvements in efficiency or cost per area

lead to lower costs per peak watt

Real Cost Data is Complicated Rapidly falling costs and prices Sometimes faster than expected, other times

slower than expected Subsidies distort prices

◦ Not just subsidies for installations (U.S., Germany, Japan, Spain)

◦ But also alleged subsidies for producers (China) Alleged subsidies have led to

◦ Large exports of solar cells from China◦ Trade dispute◦ Smaller value added for solar cell producers both in

absolute and percentage terms

http://www.economist.com/blogs/graphicdetail/2012/12/daily-chart-19

Cost Data for Different Types of Solar Cell Materials

http://cleantechnica.com/2013/01/22/chinese-solar-imports-drop-but-prices-continue-to-fall/

Real Cost Data is Complicated (2)

Hard to separate long term and short term trends Likely that Chinese subsidies for Chinese

producers have caused short term fall in prices Thus prices may go up when subsidies are gone

◦ This may be why Suntech went bankrupt in March 2013 Rising use of natural gas in U.S. has also reduced

demand for solar panels and thus prices in the U.S.◦ Firms must reduce prices or have unused capacity, so

most firms will sell below costs Subsidies also make it hard to understand which

technology might be the cheapest in the future Sources: http://sync.democraticunderground.com/112739038; http://www.nytimes.com/2013/03/21/business/energy-environment/chinese-solar-companys-operating-unit-declares-bankruptcy.html?_r=0

How do solar cells work? Improvements in cost of electricity from solar cells

Improvements in Efficiency Multi-junction cells

Improvements in cost per area Increases in scale Reductions in thicknesses

Conclusions

Outline

Maximum Theoretical Efficiency◦Similar for a wide range of materials ◦Black body limit

Best Laboratory Efficiencies◦Best efficiencies for cells produced in a

laboratory Best production efficiencies

◦Best efficiencies for cells (or modules) produced in a factory

Different Types of Efficiency

Technology Production Facilities

Laboratories Theoretical Limits

Crystalline Silicon 18% 25% 29%

Micro-crystalline silicon 14% 20% 29%

Cadmium-Indium Gallium Selenide (CIGS)

11% 20% 29%

Cadmium Telluride (CdTe) 11% 17% (20.4%) 29%

Amorphous Silicon 8% 13% 20%

Organic Cells 2% 8% (11.1%) 31%

Dye-Sensitized Cells 12% 31%

Best Solar Cell Efficiencies and Theoretical limits(for single materials in 2010)

Sources: U.S. DOE, 2010; Wang Qing and Palani Balaya (personal communication)

Crystalline materials have lower recombination of holes and electrons◦ Also high efficiencies for other crystalline materials

(e.g., GaAs) More research on silicon

◦ Longer history of silicon research than other materials◦ Silicon’s current dominance (cheaper equipment and

demand-based subsidies) reinforces this perspective Do the other materials have more potential for

improvements? And if so, how much?

Why Does Crystalline Silicon have the Highest Efficiencies?

Perovskite

DyeSensitizedCZTSSe

Organic

QD

Rapid Improvements

Quantum dots (discussed in Session 5)

Organic materials Perovskite cells

Increases in best laboratory efficiencies of organic and dye-sensitized solar cells

http://www.asiabiomass.jp/english/topics/1208_05.html

http://electronicdesign.com/article/components/organic-solar-cell-architecture-taps-next-performance-plateau

Increases in best laboratory efficiencies of organic solar cells

Improvements in Organic Cells

Many types of organic materials, but they all contain carbon◦ Many substitutions are

tried One substitution is

fullerenes Placing them in the

right place is important Synchrotron is used to

analyze the energy levels and thus the right places to place the fullerenes

Worldwide OPV production forecast

Source: Solar&Energy, Recent Organic Solar Cell Technology and Market Forecast (2010 - 2015

2000 2005 2010 2015

16

14

12

10

8

6

4

2

Rapid Improvements in Efficiency of Perovskite Solar Cells

Perovskite

Organic

Dye Sensitized

Amorphous Silicon

Perovskite-based solar cells, Hodes G, science 342, 317 (2013, Oct): 317-318

Improvements in Efficiency (1) Perovskite cells are a hybrid of organic and

inorganic materials and they have a certain type of crystal structure◦ Thus may use materials classified as other types of

solar cells◦ Key difference is in crystalline structure

Efficiencies similar to crystalline silicon are possible due to its single crystalline structure

First two cells in 2009 and 2010 were liquid junction cells that were not stable

Perovskite-based solar cells, Hodes G, science 342, 317 (2013, Oct): 317-318;http://www.technologyreview.com/news/521491/a-new-solar-material-shows-its-potential/

Improvements in Efficiency (2) Recent ones have high diffusion lengths and

long lifetimes for holes and electrons (i.e., low recombination)

Researchers have shown that it is relatively easy to modify the material so that it efficiently converts different wavelengths of light into electricity

May be possible to form a solar cell with different layers, each designed for a specific part of the solar spectrum (i.e., multi-junction cell)

Perovskite-based solar cells, Hodes G, science 342, 317 (2013, Oct): 317-318;http://www.technologyreview.com/news/521491/a-new-solar-material-shows-its-potential/

Very low cost of Perovskite (and Organic) Low-temperature deposition methods

◦ typically solution-based spin coating as compared to sputtering or vapor deposition

One-fifth the cost of current silicon-based solar cells on an area basis, due to the simpler manufacturing process

No rare materials or toxic (lead is worst material) If lifetime related problems are solved and if lab

efficiencies reach 20%, costs of $0.20 per peak Watt are expected

Perovskite-based solar cells, Hodes G, science 342, 317 (2013, Oct): 317-318;http://www.solarika.org/blog/-/blogs/new-hope-for-cheaper-solar-cells-using-perovskites

http://www.youtube.com/watch?v=oQ2bz6jlbz0

How do solar cells work? Improvements in cost of electricity from solar cells

Improvements in Efficiency Multi-junction cells

Improvements in cost per area Increases in scale Reductions in thicknesses

Conclusions

Outline

One way to overcome limitations of individual materials◦ Each has band gap that is appropriate for different part

of solar spectrum These solar cells can have

◦ much higher efficiencies than single junction ones◦ but they also have higher costs as multiple layers must

be deposited, patterned and etched One way to reduce costs is to

◦ focus sunlight onto multi-junction cells using concentrators to reduce amount of photovoltaic material

◦ but concentrating mirrors require mechanical and electronic controls, gears and other potentially unreliable components and they can only be currently used in cloudless skies

Multiple Junctions

Two-Junction Solar Cells

Ideally as you increase the number of band gaps the efficiency increases

Multiple Junctions Add Cost

For the highest efficiency solar cells, $50,000 per square meter

High costs come from maintaining crystalline structure even with 20 layers

Grown as one large crystal

Organic materials can be roll printed or sprayed on top of each other

Organic tandem cells have the same efficiencies as do single-junction organic cells

But this may change

But some incur less additional cost than others

How do solar cells work? Improvements in cost of electricity from solar cells

Improvements in Efficiency Multi-junction cells

Improvements in cost per area Increases in scale Reductions in thicknesses

Conclusions

Outline

Type of material◦ Availability in earth’s crust, Processing requirements

Number of layers◦ More layers means more processing steps

Temperature of processing◦ Higher temperatures means higher costs (e.g.,

semiconducting materials, crystalline silicon)◦ http://www.youtube.com/watch?v=F2KcZGwntgg (from 1:50)

◦ Organic materials can be roll printed

Thickness of materials◦ More difficult to reduce thickness of epitaxial formed silicon

(crystalline silicon) than thin-film deposited materials (CIGS, CdTe, amorphous silicon)

Scale of substrates and production equipment◦ Same as with LCDs and semiconductor wafers

What Determines Cost per Area?

Fewer layers Less materials Lower temperature and simpler processes

◦ Organic materials, CIGS, and Perovskite can be roll printed onto a substrate

Perhaps lower scale right now so greater potential for increases in scale◦ Many forms of thin film already use large scale production

equipment

◦ But large scale equipment has not been implemented for some technologies, particularly roll printing

◦ Roll printing is applicable to some processes and many processes for organic solar cells

Thin Film Has Potentially Lower Costs

Roll Printing of Organic Solar Cells

Roll printing of organic solar cells

Notice the simplicity

Also notice the small size of the solar cells – still a long way from reaching its optimum scale

Discussed more in two weeks

Organic solar cells, roll-to roll printing16 May 2013http://reneweconomy.com.au/2013/on-a-roll-csiro-printing-australias-largest-solar-cells-58992

How do solar cells work? Improvements in cost of electricity from solar cells

Improvements in Efficiency Multi-junction cells

Improvements in cost per area Increases in scale Reductions in thicknesses

Conclusions

Outline

http://www.economist.com/node/21543215 Source: Television Making: Cracking Up, Economist, January 21st, 2012, p. 66

Most cost reductions of LCD panels came from larger scale substrates and equipment. Similar effect for Solar

Increases in Scale of LCD Substrates (and also IC Wafers, Solar Substrates) Equipment costs per area of output fall as size

of equipment is increased, similar to chemical plants

For chemical plants◦ Cost is function of surface area (or radius squared)◦ Output is function of volume (radius cubed)◦ Thus, costs increase by 2/3 for each doubling of

equipment capacity For LCD Substrates, IC Wafers, and Solar

Substrates◦ Processing, transfer, and setup time (inverse of

output) fall as area of substrate increases since entire area can be processed, transferred, and setup together

Another Benefit from Large Panels is Smaller Edge Effects

Panel

Equipment

Effect Effects: the equipment must be much wider than panel to achieve uniformity

Ratio of equipment to panel width falls as the size of the panel is increased

Increases in LCD Substrate Size

Source: www.lcd-tv-reviews.com/pages/fabricating_tft_lcd.php

Scale of photolithographic aligners (upper left), sputtering equipment (top right), and mirrors for aligners (lower left) for LCD equipment

Source: http://www.canon.com/technology/canon_tech/explanation/fpd.html

http://www.electroiq.com/articles/sst/print/volume-50/issue-2/features/cover-article/scaling-and-complexity-drive-lcd-yield-strategies.html

Solar cells also benefit from increases in scale of production equipment

Crystalline silicon solar cells are made in wafers, just like semiconductor chips◦ Their costs fall as wafers and production equipment

are made larger, but improvements are difficult Thin-film solar is made on substrates, like

LCDs◦ Their costs fall as substrates and production

equipment are made larger CIGS and organic solar cells can be roll printed

◦ Materials can be deposited and patterned using roll-to roll printing

◦ Consider Self-Aligned Imprint Lithography (SAIL)

Increases in Scale and Solar Cells

$0.0 $0.5 $1.0 $1.5 $2.0 $2.5 $3.0

Web preparation

Sputter Gate 1 Metal

Align and Expose

SiN, a-Si, N+ dep

Align and Expose

Si RIE & Resist Strip

Ultrasonic Clean

Align and Expose

Sputter Dep/ ITO

Align and Expose

Sputter Dep Interconnect

Align and Expose

Web cost

SAIL solves alignment problem & saves money

$0.0 $0.5 $1.0 $1.5 $2.0 $2.5

Condition web (de-hydro)Gate metal deposition (Al)

PECVD oxide/nitride/Si/N+ depositionSD metal deposition (Cr)

Imprint SAIL structureWet etch Cr

RIE etch n+&Si&SINRIE etch oxide

Plasma etch Al

Thin down 2P (clear gate-pad)Pre-Cr-etch CleaningRIE etch n+&Si&SIN

Thin down 2P (clear gate-pad)Wet etch CrRIE etch n+

Under-cut Al (1-3 um)RIE etch oxide

Strip-off 2PWeb cost

cost

per

ft2

$0.00

$2.00

$4.00

$6.00

$8.00

$10.00

$12.00

$14.00

$16.00

$18.00

Photolithography SAIL

Cost of Patterning

Backplane materials costs for R2R photolithography & SAIL

R2R SAIL

R2R photolith (AGI)

Multiple photoresist applications

dominate photolithography process materials costs

2 3 4 5 6 7 8 9 1010

-3

10-2

10-1

100

eq

uip

me

nt

co

st

[M$

] /

th

rou

gh

pu

t [c

m2 /

S]

generation

equipment cost scaling comparison: panel stepper vs R2R imprinter

100 mm R2R imprinter 330 mm R2R imprinter

R2R Imprinters are much cheaper than Panel Stepper used in Photolithography

(and benefits from increases in scale)

Source: Roll-to-Roll Manufacturing of Flexible Displays, Hewlett Packard, Phicott

1 2 3 4 5 6 7 8 9 1010

-2

10-1

100 e

quip

men

t cos

t [M

$] /

thro

ughp

ut [c

m2 /

S]

generation

equipment cost scaling comparison: panel CVD vs R2R CVD

330 mm R2R PECVD

1 m R2R PECVD

Source: Roll-to-Roll Manufacturing of Flexible Displays, Hewlett Packard, Phicott

PECVD (plasma enhanced chemical vapor deposition) is also cheaper when doing R2R Printing

(and benefits from increases in scale)

Installation costs are now more than the module costs on a per Watt basis

Lower on a per Watt basis with◦large-scale than small-scale systems◦High-efficiency than low-efficiency

modules Lower on a per-area basis with thin-film or rolled materials than with thick materials (crystalline silicon)◦Just unroll a roll of organic solar cells

What about Installation Costs?

How do solar cells work? Improvements in cost of electricity from solar cells

Improvements in Efficiency Multi-junction cells

Improvements in cost per area Increases in scale Reductions in thicknesses

Conclusions

Outline

Can further decrease costs It is easier to reduce thickness of thin-film

materials than crystalline silicon◦ their thickness depends on deposition of materials◦ thickness of crystalline silicon materials depends on

cutting silicon ingots into wafers But it can also lead to lower efficiencies

◦ Less active material increases the chances that photons will pass through the material before they create an electron-hole pair

What if we can increase the amount of time that a photon spends within the material for a given thickness?◦ Thus enabling reductions in thickness

Reductions in Thickness

Rationale: Light trapping increases the optical thickness of a silicon cell by 10--‐50 times

Hence, theoretically it is possible to achieve similar efficiencies with a thinner layer material

How do solar cells work? Improvements in cost of electricity from solar cells

Improvements in Efficiency Multi-junction cells

Improvements in cost per area Increases in scale Reductions in thicknesses

Conclusions

Outline

Conclusions (1) Cost of electricity from solar cells is dropping rapidly Silicon is most widely used material

◦ Will further cost reductions for silicon occur?

◦ Or have we reached the limits?

Large number of materials and processes suggests that many improvements can still be achieved◦ Rapid increases in efficiency are still occurring for some

materials: organic, quantum dot, perovskite, multi-junction solar cells

◦ Scale up of substrates and equipment have not been done for some materials

Conclusions (2) Other improvements are also occurring

◦ Reducing thickness of materials

Installation costs are becoming larger as a percentage of total costs◦ How can they be reduced?

◦ With roll printed solar cells, or with higher efficiency solar cells?

Appendix

© Scholtes 2004 2 September 2004 Page 89

U.S. Dept of Energy Oil price forecast

Source: U.S. Department of Energy, 1998

120

100

80

60

40

20

01975 1980 1985 1990 1995 2000 2005

Year

1982

Trend predicted 1981

1984

1985

1986 1987

1991

1995

ActualDo

llars

pe

r B

arr

el

1983

http://www.wtrg.com/oil_graphs/oilprice1947.gif

BanBest Laboratory and Maximum Theoretical Efficiencies vs. Band-Gap of Material

2009 2010 2011 2012 2013 2014 20150.5

1

1.5

2

Micro (Poly) Crystalline Silicon

Cost (USD) per Peak Watt of Solar Cells

Cadmium Indium Gallium Selenide (CIGS – thin film)

Source: Lux Research (2011)

Thin Film Silicon

Cadmium Telluride (thin film)

USD

http://thinkprogress.org/climate/2011/12/11/387108/solar-power-much-cheaper-than-most-realize-study/?mobile=nc

http://thinkprogress.org/climate/2011/12/11/387108/wp-content/uploads/2011/06/Screen-shot-2011-06-08-at-3.20.01-PM.png

http://cleantechnica.com/2012/03/14/ultra-thin-solar-cell-company-unstealths-aims-to-cut-cost-of-solar-cells-in-half-images/

http://revolution-green.com/2013/07/17/solar-at-30-cents-per-watt/ http://blogs.berkeley.edu/2013/06/18/the-california-solar-initiative-is-ending-what-has

-it-left-behind/ http://www.resilience.org/stories/2013-08-16/it-keeps-getting-cheaper-to-install-solar-

panels-in-the-u-s http://energyathaas.wordpress.com/2013/06/17/the-california-solar-initiative-is-endin

g-what-has-it-left-behind/ http://thinkprogress.org/climate/2011/12/11/387108/solar-power-much-cheaper-than-

most-realize-study/

I Disagree with Conventional Wisdom Implications of learning curve (cost of producing

product falls as cumulative production increases) Although learning curves don’t exclude non-factory

activities, linking cost reductions with production ◦ focuses policy, other analyses on production of final product◦ implies that research done outside of factory is either

unimportant or being driven by production of final product◦ for solar, has encouraged demand-based policies that

subsidize installation of solar cells ($130B just in Germany) as opposed to more R&D, which has encouraged focus on existing technologies

We should first understand direct drivers of cost reduction, then develop good policy

http://electronicdesign.com/article/components/organic-solar-cell-architecture-taps-next-performance-plateau

Increases in best laboratory efficiencies of organic solar cells

Increases in best laboratory efficiencies of organic and dye-sensitized solar cells

http://www.asiabiomass.jp/english/topics/1208_05.html

Worldwide OPV production forecast

Source: Solar&Energy, Recent Organic Solar Cell Technology and Market Forecast (2010 - 2015