Walking the path from lab to start-up: printing organic solar cells

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1 Walking the path from lab to start-up: printing organic solar cells Marco Carvelli Is.tuto Italiano di Tecnologia Milano, Outline (brief) Introduc:on to bulk- heterojunc:on solar cells Challenges of present technology The Solar Print project Alterna:ve routes to the same goal Solar-Print 2 1

2 Introduc:on Solar-Print 3 Bulk HeteroJunc:on Cell Working Principle 1. Light Absorption 2. Exciton Generation R. H Friend et al., Nature 376, 498 (1995) A. J. Heeger et al,. Science 270, 1789 (1995) Solar-Print 4 2

3 Bulk HeteroJunc:on Cell Working Principle 1. Light Absorption 2. Exciton Generation 3. Exciton Diffusion Diffusion Length L D 5-15 nm Solar-Print 5 Bulk HeteroJunc:on Cell Working Principle 1. Light Absorption 2. Exciton Generation 3. Exciton Diffusion 4. Polaron Dissociation Solar-Print 6 3

4 Bulk HeteroJunc:on Cell Working Principle 1. Light Absorption 2. Exciton Generation 3. Exciton Diffusion 4. Polaron Dissociation 5. Charge Transport Power Conversion Efficiency PCE = power out / power in Mobility µ ~ 1e -3 cm 2 /Vs Lifetime τ ~ 5 µs Diffusion Length ~ 500 nm Solar-Print 7 Challenges of present technology Solar-Print 8 4

5 A more realis:c layer stack Reflecting electrode Active Blend Poor ohmic contact at blend/electrode interface (mismatch in energy levels) Transparent electrode Glass Solar-Print 9 A more realis:c layer stack Reflecting electrode n-interlayer Charge-extraction interlayers Active Blend à improve contacts à improve charge-selectivity p-interlayer Transparent electrode Glass Solar-Print 10 5

6 A standard layer stack Reflecting electrode n-interlayer Aluminum Ca Active Blend P3HT:PCBM p-interlayer Transparent electrode PEDOT:PSS Indium Tin Oxide (ITO) Glass Solar-Print 11 Problems with standard structure Glass Epoxy resin Aluminum Ca P3HT:PCBM Encapsulation Problem: Aluminum is a low-work-function metal, thus prone to oxidation heavy degradation in device performance PEDOT:PSS ITO Glass (moreover there is no low-work-function metal ink available on the market) Solar-Print 12 6

7 Solu:on: Inverted layer stack Reflecting electrode p-interlayer Silver (high work-function metal on top) PEDOT-PSS Active Blend P3HT:PCBM n-interlayer Transparent electrode ZnO Indium Tin Oxide (ITO) Glass Solar-Print 13 OPV efficiency op:miza:on pathways Reflecting electrode p-interlayer Active Blend n-interlayer Transparent electrode Glass Light-incoupling (solar concentrators, incoupling structures) Solar-Print 14 7

8 OPV efficiency op:miza:on pathways Reflecting electrode p-interlayer Active Blend Optimization of the charge-extraction interlayers (work-function, charge-transport) n-interlayer Transparent electrode Glass Solar-Print 15 OPV efficiency op:miza:on pathways Reflecting electrode p-interlayer Active Blend Optimization of the active blend (light absorption, morphology, charge transport) n-interlayer Transparent electrode Glass Solar-Print 16 8

9 Record- efficiency for BHJ solar cells PCE = 9.2% on 16mm 2 Main improvements on: active blend (low-band-gap polymer donor and PC 71 BM) electron-extraction interlayer (PFN) He et al., Nat. Photon. 6, 591 (2012) Solar-Print 17 The Solar Print project Solar-Print 18 9

10 Intermezzo: technological revolu:ons Amanuenses Printing press J. Gutenberg Middle Ages Renaissance, Enlightenment 1440 Solar-Print 19 The Solar- Print project Hand-made lab-scale OPV Roll-to-roll printed OPV Technological evolution Solar-Print 20 10

11 The roadmap at a glance G. Lanzani Solar-Print 21 About OMET Srl Omet S.r.l. is a leading company designing and producing high-technology equipment and lines to print and fold tissue paper products, self adhesive labels and flexible packaging. (from flexographic printer printing speed up to 200 m/min printed width 30 cm Solar-Print 22 11

12 From lab to industrial scale Solar-Print 23 Work- flow laboratory industry Lab-scale OPV (testing of materials and structures) (process-transfer) Printing (separate layers) All-printed OPV module (manufacturing of lab-scale devices based on printed layers) Solar-Print 24 12

13 Lab- scale cells op:miza:on Aluminum Active Blend PEDOT:PSS ITO - Silver HTL Active Blend + - ZnO ITO + Glass Standard Glass Inverted Solar-Print 25 Cell performance Open circuit voltage (V oc ) Short-circuit Current (I sc ) VOC ISC FF PCE = Power _ In Solar-Print 26 13

14 Standard! Inverted Attention points: Wettability Choice of the proper charge-extraction interlayers Few or no annealing steps Low annealing temperature Low annealing time Important for transferring technology to industrial scale Solar-Print 27 Inverted Cell Op:miza:on C urrent D ens ity [ma /c m 2 ] HTL 1 HTL 3 HTL Increasing charge selectivity Voltage [V ] Voc [V] Jsc [ma/cm 2 ] Active area = 5.25mm 2 FF [%] PCE [%] HTL HTL HTL Solar-Print 28 14

Inverted Cell Op:miza:on 20 15 C urrent D ens ity [ma /c m 2 ] 10 5 0-5 - 10-15 - 0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 Increasing charge selectivity PEIE PEI ZnO V oltage [V ] Voc [V] Jsc [ma/cm 2 ] FF [%] PCE [%] PEIE 0.

15 Inverted Cell Op:miza:on C urrent D ens ity [ma /c m 2 ] Increasing charge selectivity PEIE PEI ZnO V oltage [V ] Voc [V] Jsc [ma/cm 2 ] FF [%] PCE [%] PEIE PEI ZnO Solar-Print 29 Prin:ng / coa:ng techniques we use Bar Coating Characteristics: film thickness controlled by changing the wires/wiring pitch and the solid content of the ink à no fine-tuning of thickness limited patterning Solar-Print 30 15

Prin:ng / coa:ng techniques we use Spray Coating Characteristics: film thickness controlled by changing the spraying time and the solid content of the ink à fine-tuning of thickness patterning via

16 Prin:ng / coa:ng techniques we use Spray Coating Characteristics: film thickness controlled by changing the spraying time and the solid content of the ink à fine-tuning of thickness patterning via masks Solar-Print 31 Prin:ng / coa:ng techniques we use Flexography Characteristics: film thickness controlled by changing the anilox volume and the solid content of the ink à fine-tuning of thickness implies the use of different anilox rolls patterning via photopolymer photopolymer Solar-Print 32 16

Cri:cali:es Annealing time is limited (1 min max) Annealing temperature is limited (150 C max) Use of toxic solvents shall be avoided (liters consumed) Everything processed in air Viscosity must be

17 Cri:cali:es Annealing time is limited (1 min max) Annealing temperature is limited (150 C max) Use of toxic solvents shall be avoided (liters consumed) Everything processed in air Viscosity must be finely tuned Solar-Print 33 Issue with ﬂexography: the printed surface is not ﬂat Fingers height 500 nm low volumes (3.3 cm3/m2) larger fingerpitch lower resistivity high volumes (21.5 cm3/m2) printing direction Solar-Print 34 17

Viscous fingering Viscous fingering is the formation of patterns in a morphologically unstable interface between two fluids in a porous medium or in a Hele- Shaw cell.

18 Viscous fingering Viscous fingering is the formation of patterns in a morphologically unstable interface between two fluids in a porous medium or in a Hele- Shaw cell. It occurs when a less viscous fluid is injected displacing a more viscous one (in the inverse situation, with the more viscous displacing the other, the interface is stable and no patterns form) (Wikipedia) Solar-Print 35 Viscous fingering Solar-Print 36 18

19 Printed conduc:ve inks R S < 1 Ω/sq (R S, ITO = 15 Ω/sq) Solar-Print 37 Alterna:ve routes to the same goal Solar-Print 38 19

20 We are not alone.. POLYMER PVs SMALL MOLECULES PVs CIGS PVs University of Cambridge, UK, 2011 Imperial College, UK, 2011 USA, 2002 Spin- off of DISA Group, France, 2008 former Konarka GmbH, Germany, 2012 Technical University of Dresden and University of Ulm, Germany, 2006 USA, 1996 (expensive inorganic materials involved) founds Flexsolar with Cromotranfer, Brazil, 2012 Solar-Print 39 Compe:tors at a glance Competitor Power Conversion Efficiency Highlights Status Partnerships Eight19 7% lab scale on PET from lab to R2R Material providers (Rhodia) Solar Press 7% lab scale on glass Not available Not available Disa Solar 2% on 225cm 2 on glass From sheet-tosheet to R2R French government, Solliance Belectric OPV 8.3% on lab scale (Konarka) 5% panel (Konarka) Not available Not available Flexsolar Not available Not available Fraunhofer IAP Heliatek 12% on lab scale tandem cell (world record) Pilot line ready University of Ulm, BASF, Bosch, RWE, Reckli (buildingintegration) Solar-Print 40 20

cell performance by adding mul6ple layers Cons max produc6on speed: 1.

21 Small- molecule PV Roll- to- roll evapora:on of tandem solar cells in vacuum Pro high control of surface roughness and layer thickness homogeneity op6mize the cell performance by adding mul6ple layers Cons max produc6on speed: 1.5 m/min Solar-Print 41 Copper- Indium- Gallium- Selenide PVs Solar-Print 42 21

22 CIGS- PV CIGS (Copper Indium Gallium Selenide) solar cells produc6on by R2R deposi6on on aluminum Status: ready for produc6on Pro 17.1% on lab scale, 10% on large scale proprietary inks Cons rare elements involved (Indium, Gallium, Selenium) thus intrinsically expensive high temperatures involved (larger than 200 C) à plas6c substrates excluded prin6ng on aluminum, thus non- transparent Solar-Print 43 The best is yet to come Solar-Print 44 22

Rigid Solar-Print 45 Lightweight a key factor

23 Present PV Technology Market Largely Dominated by Si Durability PROS CONS Weight Efficiency Costs Rigid Solar-Print 45 Lightweight a key factor Kaltenbrunner et al., Nat. Comm. 3, 770 (2012) Solar-Print 46 23

24 Cost effec:ve cells Solar-Print 47 Cost effec:ve cells Solar-Print 48 24

25 Cost effec:ve cells Solar-Print 49 Cost effec:ve cells Solar-Print 50 25

26 Cost effec:ve cells Solar-Print 51 Cost effec:ve cells Solar-Print 52 26

27 OPVs: a fast growing market Today: 4.3 Million USD 1300 % 2022: 630 Million USD IDTechEx Report, May 2012 Solar-Print 53 On the longer term... EDEN Project, UK m 2 National Acquatic Center, China m 2 MediaTIC, Spain m 2 Kingsdale School,UK m 2 Is6tuto Italiano di Tecnologia 54 27

Ecole ECOCLIM2018 Le solaire photovoltaïque.

Ecole ECOCLIM2018 Le solaire photovoltaïque yvan.bonnassieux@polytechnique.edu Summary q Energetic context q Solar cells: Operating principle q Comparison crystalline/amorphous silicon cells q Photovoltaic