The Challenges of Organic Polymer Solar Cells

1/25/11

Prepared by Burhan Saifaddin

Advisor: Prof. Jeffrey Grossman

Arab Research Seminar

27 January 2011

1

• Introduction• Polymer Solar cells technology and

challenges• Commercialization prospects in Grid

electricity markets• Commercialization prospects in Niche

markets.• Conclusion

Presentations Outline

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Meeting huge Energy demand Sustainably.2010 15 TW ; 2050 30 TW (peak)

Hedge against the risk of Global warming.Energy Security Economic growth. Reducing energy costs to increase human development.

Significant Energy Challenge

Figure adopted from woodruffcenter.org

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AAAS voted electrification to be the most important technology developed in 20th century. Electrification affected productivity far more than IT (at least up to 1990 but IT is dependent on Electrification).**

Developing world

** David, P. (1990). "The dynamo and the computer: An historical perspective on the modern productivity paradox." The American Economic Review: 355-361. 

Figure adopted from NYT

In most of these areasSolar insolation > 1.5 MWh/m2/year

Electricity cost< 1 $/WpPreferably 0.25 $/Wp*

• Gates Foundation

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Long-term future of PV

1/25/11International Energy Agency (IEA), www.iea.org/techno/etp/ETP_2008.pdf

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PV electricity generation share now is around 0.1 %

Current Status of Polymer PV

• Low efficiency 2-3 % for modules.• Small area Lab cells over 8% by Konarka, Solarmer.• Heliatek Lab cells over 8%.• DSSC module close to 10%.

Figure adopted from DOE1/25/11 6

2010 Oil Production

Production 8 Million b/day (10% global production).

Production capacity of ~12 Million barrel a day.

Current oil consumption is equivalent to 3.2 million barrel a day in electricity, water, transportation and industry.

Saudi Arabia Global Energy Challenge

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Current oil consumption is equivalent to 3.2 million barrel a day in electricity, water, transportation and industry.

Demands have increased by 27% over the last three years.

2032 Electricity demands will trouble ; additional 80 GW

Very challenging politically to decrease consumption rate.

Saudi Arabia Global Energy Problem

04/08/2023 8

2010 2015 20280

2

4

6

8

10

12

14

16

3.2 3.6

88

10

12

15 ? ?

Oil Consumption and Production - 8% energy conuption

ConsumptionProduction Capacity

Mill

ion

Barr

el p

er D

ay

Data : Khalid A. Al-Falih Saudi Aramco CEO.

Current oil consumption is equivalent to 3.2 million barrel a day in electricity, water, transportation and industry.

Demands have increased by 27% over the last three years.

2010 consumption 3.2 Million b/day

2028 Projected consumption 8 Million b/day

2032 Electricity demands will trouble ; additional 80 GW

Very challenging politically to decrease consumption rate.

Saudi Arabia Global Energy Challenge

Data is based on a speech by Hashim Yamani, president of King Abdullah City for Atomic and Renewable Energy, at GCF 2011.1/25/11 9

Put Oil into a better use !

Comparison of energy obtained from an Oil barrel Vs its equivalent in Polymer / Small Molecule solar cell

We know thatBarrel of oil equivalent  (159 liters) = 1.7 MWh Average Solar Energy 1-3 MWh /m2/year; if we use 10%  PV system with 10m2 of solar panels we get the same amount.

We can assume thatPolymer Solar cells uses 1g/m2 of active material10 Oil grams yield 1 gram of active material

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Put Oil into a better use !

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In one year, an energy equivalent to ~10,000 grams of oil can be produce by 1 g of active material. (i.e. 0.11-0.14 MWh, depending on the Oil type and assuming that.

So instead of burning 365 Million barrels over a year make solar cells from 36.5 Thousands barrels. Also,Polymer solar cells energy yield much less CO2/ joule Polymer Solar cells is fully recyclable.Polymer solar cells payback time is less than 1 year at reasonable efficiency.

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Basic Overview of the TechnologyRoll to Roll processing. Cheap abundant Materials. Light weight.Mechanically Flexible. Flexible FormColor Larger acceptance angle. Positive thermal coefficient. Work better at low light conditions.

Low life time (2-4 years) and low efficiency (3-3.5%).

Konarka (2001)Plextronics (2002) Solarmer (2006)

Similar Technologies Small Molecules: Heliatek

DSSC: Dyesole, G24i1/25/11 12

What is polymer solar cells ? Donor-Acceptor Heterojunctions

K. Coakley, M. McGehee, Chem. Mater 16, 4533 (2004). ;C. Deibel, V. Dyakonov, Reports on Progress in Physics 73, 096401 (2010).

Strong absorbers of light ~ 100 nm but narrow absorption widthLimited exciton diffusion length 5-10 nmDoes more optimized synthesis routes of polymer increase their exciton diffusion length ? How this impacts simulations ?

A. Ayzner, C. Tassone, S. Tolbert, B. Schwartz, The Journal of Physical Chemistry C 113, 20050 (2009).1/25/11 13

How polymer solar cells work ?

C. Deibel, V. Dyakonov, Reports on Progress in Physics 73, 096401 (2010). 1/25/11 14

(i) Light absorption and exciton generation.(ii) Exciton diffusion.(iii) Exciton Dissociation at the interface and then +/- charge carriers

(Polarons) separation at the interface.(iv) Charge carriers diffusion toward electrodes. (v) Charge extraction by electrodes.

Efficiency Discussion for single layer

Assume FF = 70% (Dark current, Voltage dependent current )

Loss in Voc=0.3 (-20%)

Isc = Photons energy

absorbed*EQE

Practical single layer efficiency~ 15%

Limited band absorption

Assume Band Gap=1.4 eVIn inorganic, typical single junction S-Q efficiency is ~ 30% at optimal bandgap (band aprorption). Assume EQE 90% (electron/

#photon)

Figure adopted fromC. Deibel, V. Dyakonov,Reports on Progress in Physics 73, 096401 (2010).

Assumes Isc is the result of absorbing 30% of # solar photons

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Practical single junction efficiency

Scharber, Brabec et al. Advanced Materials 18 (2006) 789.

EQE = 65%FF=0.65

Guidelines for chemists to new more efficient materials 1/25/11 16

Tandem Cells efficiencies

1/25/11Very Wide absorption bands 300 nm absorption bands

C. Deibel, V. Dyakonov, Reports on Progress in Physics 73, 096401 (2010).

EQE 80%, Voc loss =0.2 V

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Degradation : active materials, PEDOT, electrodes, substrates.

M. Jørgensen, K. Norrman, F. C. Krebs, Solar Energy Materials and Solar Cells 92, 686 (2008).

 

Lifetime

G. Schwartz et al., Proc. of SPIE, 7416 (2009)

On the other hand, Small Molecule startup Heliatek used accelerated lifetime testing to estimate lifetime > 30 years.

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What needs to be done about efficiency ?

• More research need to be done on life time. • It is experimentally hard, simulation might be

a way.• There is no road map for lifetime as there

road maps for efficiency.

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Encapsulation

C. Lungenschmied et al., Solar Energy Materials and Solar Cells 91, 379 (2007).

Is ultra thin film barrier sufficient ?

3M is commercializing an “transparent ultra barrier solar film” with moisture vapor transmission rates (MVTR) below 5*10-4 g/m2/day “and with excellent durability and weatherablity for 25 years”2011: 4.4$ from SunShot initiative.

Encapsulation is possible theProblem is in the intrinsicmaterial lifetime

There are encapsulants with similar performance for OLEDs.Konarka developed encapsulations but with less performance than glass .

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OPV Module Vs Si ModuleCost

Figure adopted from HiscoFigure adopted from Konarka

9.1%

4.2%

52.7%4.2%

11.5%

7.4%

10.8%

Barrier 9.1%

Pressure sensitive adhesive 4.2%

PET-ITO 52.7%

ZnO 4.2%

P3HT-PCBM 11.5%

PEDOT:PSS (EL-P 5010) 7.4%

Silver (PV410) 10.8%

F. Krebs, S. Gevorgyan, J. Alstrup, Journal of Materials Chemistry 19, 5442 (2009).

Cost of c-Si 1.7 $/Wp at 15% efficiency Cost of CdTe ~ 0.7 $/Wp at 12%Polymer solar cells must improveefficiency over 10% and have large lifetimeITO need to be replaced.

New module designs are neededto reduce installation costs.Also, innovations in installation methods.

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How much can flexible Solar reduces installation costs ? There is a lot of hype.

a-Si SoloPower a-Si Uni-Solar Plastic covering a strawberry field

DOE White Paper, www1.eere.energy.gov/solar/pdfs/dpw_white_paper.pdf

PV.http://photosbygarth.com/samples‐lg/050115_202p_9584lg.jpgPolymer module can have less

installation cost can than a-Si flexible but polymer module need to generate comparable energy over its lifetime.

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Future Commercialization in electricity grid market

Utility PV installation c-Si Glass Module efficiency~ 15%. Does not include grid infrastructure and storage cost. (Data DOE White Paper)

Assume after 5-10 years,polymer solar cells can have 7% efficiency and 7 years lifetimeAlso assume a polymer module cost 50$/m2 and all non module costs at 70$/m2. (actual $/Wp will be high because of low average efficiency _ it is not fair to compare these efficiencies with inorganic efficiencies )The PV system will generate electricity at 10 c/kWh*. How easy is to bring non-module costs at 70 $/m2 ?

10%

40%

50%

Cost breakdown for a c-Si Utility PV system in 2010. Total cost =~480 $/Wp (3.4 $/Wp)

Inverter 33 $/m2BOS and Labor 222 $/m2Module 225 $/m2

Rooftops has higher installation cost > 60%

Wiring 21 $/m2Labor 57 $/m2

System design 22.5 $/m2

Total ~ 100 $/m2

* Konarka Study : G. Dennler, M. Scharber, C. Brabec, Advanced Materials 21, 1323 (2009).

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Potential New Abundant Materials

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MIT Energy Workshop on Critical Elements for New Energy Technologies | April 29, 2010C. Wadia, A. Alivisatos, D. Kammen, Environ. Sci. Technol 43, 2072 (2009).

Rollable installation ~ (>25% drop in installation cost)Do it yourself Solar ~ minimal installation cost – need new innovations.

Flexible Module Installation on Rooftops

Costs Cost Unit  Low Estimate$/m2

Low Estimate Percentage %

Module $/m2 255 43.6%Inverter $/m2 45 7.7%

Rack $/m2 60 10.3%Labor $/m2 120 20.5%

Project costs $/m2 60 10.3%

Sales commission 0.00% 15 2.6%Sales tax 0.10% 30 5.1%

Total PV system Cost   585 -

The cost breakdown for a 200kWpcommercial PVinstallation in Boston.(Data form Borrego Solar, MA).

$/Wp depends strongly on efficiency and Present Value of lifetime

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Lower installation cost : Lighter module, no frames, no racks

Advantages of Flexible Substrates

79.699%

14.574%

1.139% 0.001% 0.000% 0.003%

Module Weight Percentage% Total Weight* 10-100 g/m2

Polyimide substrates 7.970E-01ITO 1.457E-01PEDOT:PSS 1.139E-02P3HT/PCBM 1.163E-05LiF 3.488E-07Al 3.488E-05

Konarka solar modules ~ 1 kg/m2 Solarmer solar cells ~100 g/m2.

a-Si Uni Solar Modules ~ 10 kg/m2

c-Si/CdTe modules 10-20 kg/m2

Put reference here 1/25/11 26

Drawbacks of Flexible Substrates

• Drawbacks:– Less efficiency than glass.– Flat installation can lead to less energy yield (by 20 or

more). – more heating and less ventilation, possibility of heating the

roof and the house.– How durable is flexible solar substrates ?

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Levelized Cost of electricity

Effect of Efficiency Effect of life time

(dependent on P.V.) Effect of Interest Rate

High efficiency, long lifetime PV technologies has more advantage in reducing the dominant non-

module costs

Figure adapted from Prof. Tonio Buonassisi

New module designs are neededto reduce installation costs.Also, innovations in installation methods.

Figure adopted from DOE

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BIPVSolar Shingles Facades, etc

Reduction in installation cost.Reliability.Need various forms. It can not eliminate all installation cost.

Commercialization Challenges in on Niche Markets

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Niche Markets• Opportunities is determined by

– $/kWh, life time, efficiency.

• Light Weight and low light suitability. • Portable Electronics: Mobiles , laptobs , ipods• Watches.

• Flexibility– Clothing. – Fabrics. – Tents

• Transparency – Tinted Glass.– Building integrated materials.– Automobiles.

Cost ~ 10$/Wp

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Portable Power

• Current PV system cost is too high ~10$/Wp• It is not for indoor lighting ! (1-2% of sunlight).How long does it take to charge under the sun?

Cost 100$

10 W300 $30 $/Wp

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Conclusion • To bring down installation cost in electricity markets polymer

solar cells need to have large efficiency (10%) and long lifetime (> 10 years).

• To compete in Niche markets durability is essential.• New modules designs and new innovative installation

methods are needed to bring down the cost of PV systems. • More understanding of degradation mechanisms is needed

to ; new characteristics tools are needed to study degradation.

• Average efficiencies over a specific lifetime should be taken into account when comparing performance.

• Do not loss hope on polymer solar cells. 1/25/11 32

Acknowledgment

• My Advisor.• King Abdul-Aziz City of Science and

Technology. • My Family.

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Thermal Effects

• Organic PV has a positive temperature coefficient.• Record efficiencies are usually calculated at 25 C. Typical operating temperature varies depending on the

location , technology type and application • Operating temperature is typically 40-65 C. at about 10% increase in efficiency

www.konarka.comSarah Kurtz, NREL [http://www.nrel.gov/docs/fy10osti/49176.pdf]

+0.05% / ºCOver 40 to 60

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Organic Record Cells Status

Both Companies plan to enter grid market by ~2015. Can they ?

NREL, 2004

Recent records~8.3% by Konarka, Solarmer, and Heliatek

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Energy Payback time

1/25/11 A. Anctil, C. Babbitt, B. Landi, R. Raffaelle. (IEEE), pp. 000742-000747. 

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Efficiency limits

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Voc loss =0.2V

Assume limited 300 nm absorption band

Lower refractive index raises

the optimal band gaps

C. Deibel, V. Dyakonov, Reports on Progress in Physics 73, 096401 (2010). 37

Grid Parity

www.mckinsey.com/clientservice/ccsi/pdf/economics_of_solar.pdf1/25/11 38

Average PV Installed Cost 2009

1/25/11 http://cleantechnica.com/ 39

Energy at MIT

• Companies :MIT: 1366 , A123, MA :1/25/11 40

PV learning curve

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Learning curve for the cost of PV systems, module prices, and BOS cost. Source Navigant Consultant Adopted from DOE [http://www1.eere.energy.gov/solar/pdfs/dpw_chu.pdf]

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Konarka Module

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Solar Cells in Saudi Arabia ??

• Oil Cost. : opportunity cost• Energy Prices in Saudi !!• Future Electricity Demands

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Current PV Systems comparisons

DOE1/25/11 44

Solution processed transparent electrodes

• Disadvantages of current electrodes : metal fingers shading, oxidation of low work

function electrodes … ITO energy intensive (sputtering), costly, brittle:

Lab cell opv energy pay back time is at x % efficiency. Solution processed TCOs:metal mish, Graphene. transparency of more than 90% and a sheet

resistance of 10 Ohm/sq more is needed for polymer solar cells in monolithically integrated modules

M. Rowell, M. McGehee, Energy Environ. Sci., (2010).H. Park, J. Rowehl, K. Kim, V. Bulovic, J. Kong, Nanotechnology 21, 505204 (2010).J. Lee et al. (IEEE, 2010), pp. 002200-002203.J. Wu et al., Applied Physics Letters 92, 263302 (2008).1/25/11 45

SunTech view on Power electronics

Prospects for module integration with Power electronics (as in IC)

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Fullerenes Production Challenges

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• Impact of conductivity

• Discuss Efficiency • • Elaborate on Markets

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Competing Technologies

• Polymer Solar Cells• Small Molecules• Cu2O (excitonic solar cells )

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