Printable Organic Solar Cells Challenges and Opportunities in Technology Transfer from Lab to Market

Transcription

1 Power Plastic R Printable Organic Solar Cells Challenges and Opportunities in Technology Transfer from Lab to Market Alan J. Heeger Chief Scientist and Co-Founder 116 John Street, Lowell, MA 01852

2 Plastic Solar Cells Confidential

3 Click to edit Master title style Second level Third level Fourth level Fifth level Lightweight, flexible and rugged! 3

4 Conversion of Sunlight into Electricity Three step process 1. Absorption of photons in a material 19 th Century Chemistry 2. Photo-induced charge separation 20 th Century Chemistry/Physics 3. Collection of charges at electrodes 21 st Century Chemistry, Physics and Materials Science

5 Semiconducting Polymers inks ----with electronic functionality! Roll-to-roll manufacturing of plastic solar modules at Konarka facility in New Bedford, MA

6 The Idea ---- ħω RO RO OR OR 50 fs RO OR e- RO OR Bulk Heterojunction Material

7 Bulk Heterojunction Morphology Effect of Heat Treatment Before 150 o C anneal 150 o C anneal 30 min 150 o C anneal 2 hours OMe O S n P3HT PCBM

8 Manufacturing Technology Energy for production (MJ.Wp -1 ) CO 2 footprint (gr.co 2 -eq.wp -1 ) A. L. Roes et al, Progress in Photovoltaics 17, 372 (2009) Energy payback time (years) mc-si CdTe CIS Flex OPV

9 Bulk heterojunction Solar Cells - + Al PEDOT:PSS ITO Glass Thin Film of Phase Separated Bulk Heterojunction Material Light Semiconducting polymers Solution processed Fullerene derivatives Solution processed Nano-structure self-assembles --- Spontaneous Phase Separation

10 Technology Overview Buss Bar Electrode Printing Techniques +Synthetic Materials = Scalability Active Layers Substrate Encapsulation

11 Leverage Existing Capacity Retrofit existing printing facilities: Low CAPEX: Fast Ramp-up High Yield Output Quantity: - Web Width: 1.5 meter - Speed: 30 feet/min - Output equals: 1.0 GW/yr* * 5% module efficiency 200 nm active layer (1:1 D/A) 2,000 Kg of Donor 2,000 Kg of Acceptor Active material cost of 4

12 Performance Requirements Lifetime Efficiency Cost Lifetime 3 to 5 years - flex encapsulate / 15 to 20 yrs - glass encapsulate Cost <$50/sq.meter Efficiency Translates to $1 5% eff.

13 Optimization Absorption of the incoming photons η η. η. η device abs CT collection 1.0 5x10 14 AM1.5G / Photons.cm -2.s -1.nm -1 4x x x x Fraction of photons in AM1.5G Wavelength / nm

14 Absorption Spectra of KTI Low-Band-Gap Polymers Compared to That of P3HT ZZ50 ZZ72 ZZ73 P3HT S P3HT n S S ZZ50 N S N n S S S N N ZZ72 n S S S N N ZZ73 n

15 Origin of Voc and the Built-in in Potential π*-band LUMO V oc π-band HOMO V OC E fullerene (LUMO) E polymer (HOMO)

16 J sc - Absorption across solar spectrum (UV IR) Charge transfer and charge separation; mobile carriers Competition between carrier sweep-out by internal field and carrier recombination Morphology and connectivity of phase separation V oc 1 e ( Fullerene Polymer ) B e h E Δ ln LUMO EHOMO e Nc = 2 FF - Recombination (hole in polymer, electron in fullerene) k T n n V oc (V) Temperature (K)

17 Physics of carrier recombination: Voltage region 1: Independent of Intensity, first order (monomolecular) Normalized Photocurrent (A.U.) Voltage region 2: Sub-linear, bimolecular Voltage (V)

18 Physics of carrier recombination: V oc 1 e ( Fullerene Polymer ) B e h E Δ ln LUMO EHOMO e Nc = 2 where Nc= density of states in the band tails k T n n Universal dependence Seven different Semiconducting polymers δ V oc kt e ln ( I ) np ~ I Bimolecular --- slope not 2

19 V OC = 0.88V FF = 64% Power Conversion Efficiency = 6 % Property of Konarka Technologies, Inc.

20 17% Power Conversion Efficiency for wavelengths within the absorption band Current Density (ma/cm 2 ) ITO/PEDOT:PSS/PCDTBT:PC 70 BM/TiO x /Al Input power : mw/cm 2 (532 nm) Voc : 0.86 V Jsc : 6.0 ma/cm 2 FF : 0.65 Efficiency: 17.0 % Voltage (V) High efficiencies are possible --- But: Absorption spectrum is not well matched to the solar spectrum --- no absorption beyond 650 nm. Improve the performance by reducing the band-gap and improving the morphology. Property of Konarka Technologies, Inc.

21 Importance of the nano-morphology Example: Si-PDTBT:PC70BM 1:1 I SC η. η. η abs CT collection with Chloro-napthalene as processing additive Without processing additive With Processing additive Top down Cross section Top down Cross section Double the Efficiency!

22 Plastic BHJ solar cells can be a 20% technology

23 Efficiency Outlook Efficiency (%) United Solar University of Lausanne NREL United Solar NREL NREL NREL NREL Thin Film Technologies Cu(In,Ga)Se 2 CdS/CdTe a- Si/a-SiGe Emerging PV Dye cells OPV (polymer) Sharp Konarka EPFL (SSDSSC) Solarmer Konarka OPV single junction UCSB 1995 Cambridge U. Linz 2000 Konarka Konarka Siemens Siemens Year 2005 Plextronics 2010 Single junctions to break 10% by Multijunctions technology to drive efficiencies beyond UCSB 4 0 Property of Konarka Technologies, Inc.

24 Industrial potential- Green Polymer EQE Wavelength / nm Active Layer 200 nm Green appearance (T)

25 OPV in Windows: Building Integrated Applications

26 Excited state and charge transfer t < 200 fs t < 200 fs Mobile carriers sweep out by the internal voltage (built-in electric field) hν Interfacial traps and Interfacial excitons Ground state Recombination Necessary for high efficiency: 1. Ultrafast charge transfer and generation of mobile carriers 2. Sweep-out by internal field prior to recombination

27 Transient photocurrent in operating solar cell P3HT:PCBM J / V int (mω -1 cm -2 ) V 0.5V 0.4V 0.2V 0.0V -0.5V -1.0V τ sw 0.1 μs τ R 5 μs Time (μs) Sweep-out is faster than recombination and therefore --- high efficiency

28 R2R Manufactured Module Performance 0.02 AM1.5G Dark 0.00 Current [A] V oc =5.64 V FF=58 % i sc =91.4 ma P out =299 mw Applied Voltage [V] 10 stripe modules. monolithic interconnection AM1.5 3 % from high band gap polymer 4 % from low band gap polymer Indoor efficiency at >5 %

29 Lifetime of Production Modules WVTR Barrier 1 >> WVTR Barrier 2 >> WVTR Barrier 3 Norm. Eff. [a.u.] C/85%rh Barrier 3 Barrier 1 Barrier Time Hours Depending upon the adhesive/barrier used the lifetime of the modules can be impacted profoundly.

30 Outdoor Testing - Konarka Location Lowell, MA. Facing solar south at kwh / m 2 Two measurement modes a) Outdoor jv in 4th quadrant with modulated load and wireless data read out b) Periodic characterization under standard solar simulator Lowell, MA Southern Florida Southern Arizona

31 Outdoor Performance

32 Key Technology Features Advantages of OPV flexible thinfilm solar technologies: Tunable cell chemistry can absorb specific wavelengths of light as well as broad spectrum Less sensitive to angle of solar incidence Positive thermal efficiency coefficient Flexible, thin, light-weight Printable in various widths-roll-to-roll Low light sensitivity (indoor/outdoor) Semi-transparent for window applications

33 Click to edit Master title style Second level Third level Fourth level Fifth level Lightweight, flexible and rugged! 33

34 Thank you for listening Questions?