HomoOPV - High Efficiency Homojunction Organic Photovoltaics

Transcription

1 HomoOPV - High Efficiency Homojunction Organic Photovoltaics Sebastian Dunst 1, Gregor Trimmel 1, Mihai Irimia-Vladu 2 1 Technische Universität Graz, Institut für Chemische Technologie von Materialien 10 % 2 Joanneum Research mbh, Department of Materials, Institute for Surface Technologies and Photonics

2 2 Energy Mission Austria: e!mission: High Efficiency Homojunction Organic Photovoltaics (HomoOPV) Project Duration: 2,5 years

3 Do we need other technology converting solar cell radiation into electricity? 3 World year demand of electricity: TWh Supplying this by installing (mostly) silicon based PV would require km 2 of suitable land Today we install only 500 km 2 /year of (mostly) silicon PV panels 200 years necessary to fulfill global demand The alternative PV technology has to be compatible with high throughput manufacturing leading to light weight & flexible products and fast deployment of PVs on a large scale Account for environmental friendliness

4 4 Source: M. McGehee (Stanford Univ. Materials Science and Engineering) Seminar, 2014

5 Silicon PV 5 csi High temperature production Energy intensive Lab efficiency ~25% Module efficiency ~18-19% Rigid and heavy weight

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9 Alternative PV concepts to c-si 9 Dye sensitized solar cells (DSC) Organic Solar Cells Quantum Dot Solar Cells CZTS Solar Cells Perovskite Solar Cells (PSC)

10 10 Organic Photovoltaics Solar Cell Park 250 m 2 platform; series cells; fill factor > 60%; fabrication speed = 0.3 m/sec. / individual cell of 7cm 2 ; Installation speed > 100 m/min (up to 300 m/min possible) Module PCE of only 1.85% In Denmark: payback in 277 days In South Spain: payback in 180 days 137 km 2 necessary to produce 1 GW peak at this performance F. Krebs et al, Adv. Mater. 2013, DOI: /adma

11 11 Organic Photovoltaics: How an OPV works

12 Organic Photovoltaics-Parameters

13 Conjugation, charge delocalization and transport: key issues of organic semiconductor design Pentacene Mobility 1-2 cm 2 V 1 s 1 in thin films 3-5 cm 2 V 1 s 1 in single crystals Mobility 15,000 cm 2 V 1 s 1 Rubrene Mobility 40 cm 2 V 1 s 1 in single crystals Are there conjugated molecules in nature?

14 H-bonded classes of molecules

15 Hydrogen bonding is ubiquitous in nature: e.g. DNA, cellulose cellulose guanine cytosine and has been exploited for technology Kevlar, a synthetic fibre with exceptional strength

16 Why H-bonded Pigments were not considered good candidates for Organic Semiconductors Conjugation and the resonance model Amine: Carbonyl:

17 H-bonded pigments: why are they still highly conjugated? Quinacridone 2,3,9,10 positions hydrophobic G. Lincke, Dyes and Pigments 52, 169 (2002) E.F. Paulus et al., Cryst. Eng. Comm. 9, 131 (2007)

18 Quinacridone γ-phase criss-cross _ View direction [130] View direction [001]

19 Quinacridone β-phase linear-chain View direction [100]

20 A remarkable feature of the H-bonded dyes is long range ordering in the solid state and a resulting high dielectric constant Material HOMO (ev) LUMO (ev) E g CV (ev) E g optical (ev) Carrier Mobility, (cm 2 / V s) Relative permittivity (e r ) Indigo Tyrian Purple Cibalackrot m e = , m h = m e = 0.3, m h = m e = , m h = Quinacridone m h = Epindolidione m h = 1 N/A

21 Organic materials have low relative permittivity compared with inorganic semiconductors Permittivity is the measure of the resistance that is encountered when forming an electric field in a medium Highly polarizable media reduce electric field E B m e e 2

22 Low dielectric constant of organic solids results in high exciton binding energy Titel/Ersteller, Datum

23 Energetic offset LUMO-LUMO > Exciton binding energy

24 The donor/acceptor interaction causes polarization of the exciton into free charges Photoinduced electron transfer

25 Soluble polymer-fullerene mixture enable printable bulk heterojunction devices

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27 Quinacridone-ambipolar OFETs with Ag S-D electrodes! m e =m h =0.01 cm 2 /Vs Eric Glowacki et al.-adv. Mater. 25, 1563, (2013)

28 Eric Glowacki et al.-advanced Materials-25, 1563, (2013)

29 Excimeric states dominate the optical behaviour of quinacridone in the solid state

30 Quinacridone single-layer solar cells show EQE >100 higher than typical conjugated molecules No enhancement of EQE with addition of C 60 Glowacki et al. APL-(2012)

31 Temperature dependence of photocurrent suggests low effective exciton binding energy ~ 12 mev in Quinacridone Quinacridone 500 µm 1 mm CW-Green laser excitation E.D. Glowacki et al. APL-(2012)

32 Low dielectric constant of organic solids results in high exciton binding energy Inorganic semiconductors Organic semiconductors

33 33 Investigated molecules (vacuum processible)

34 Investigated molecules (solution processible) 34 Quinizarine

35 Shrinking the list of candidates Sudan Blue Solvent Green Sudan Blue II Oil Blue N 35 Abbildung 1: Mikroskopie DAAQ-Derivate aus CHCl 3 -Lösungen Alizarin Quinizarin Chrysazin Purpurin Abbildung 1: Mikroskopie Hydroxyanthrachinone aus DMF-Lösungen

36 ev HOMO-LUMO in Solution HOMO Level [ev] LUMO level [ev] -4-3,6-3,55-3,6-3,55-3,55-3,55-3,6-3,55-3,6-3,8-4 -3,95-3,9-4, ,2-5,1-5,55-4,95-4,95-4,95-5,1-5,8-5,95-5,95-7 HOMO-LUMO Thin-Film 0,00 0,00 0,00-1,00-2,00-3,00 HOMO Level [ev] LUMO level [ev] -4,00-3,57-3,56-3,47-3,51-3,73-3,71-3,77-3,79-3,89-3,77-3,79-5,00-5,09-5,01-6,00-5,55-5,50-6,03-5,95-5,79-5,99-5,97

37 Determined optical band width 37 Tabelle4: ermittelte optische Bandlücken ausgewählter Farbstoffe Farbstoff Chrysazin Quinizarin Alizarin Anthrarufin Purpurin Sudan Blue Sudan Blue II Oil Blue N Solvent Green optische Bandlücke/eV (Lösung) optische Bandlücke/eV (Dünnfilm) 2,58 2,3 2,38 2,58 1,9 1,86 1,85 1,85 1,81 2,06 1,96 2,12 1,82 2,02 1,57 1,76 1,69 1,58 Excellent solubility in a wide range of organic solvents

38 Chrisazine single layer OPV cells from CHCl 3 38 Hydroxilated Anthraquinones most probably do not work in single layer OPV

39 39 Remained molecules (vacuum processible)

40 Protect-deprotect route can be used to make films t-boc quinacridone Dissolve and spin coat from CHCl 3 or Ph-Cl 160 o C

41 AFM of Vacuum vs. Solution processible molecules 41

42 I-V curves Disperse Blue I 42 Very low PCE indeed but Disperse Blue I is an ambipolar semiconductor!!!

43 43 Pigment Red 122 (dimethyl Quinacridone)

44 44 ITO TiO x PigmentRed122 PEDOT:PSS Ag V OC /mv I SC /ma/cm² FF /% PCE /% 2x x x x

45 Evaporated cells 45 Pigment Red 202 (dichloro Quinacridone) PCE = 0.1% with Ca-Al back electrode

46 Solution processed cells 46 Comparison Evaporated vs. Solution Processed

47 Quinacridone cells evaporated - regular PCE = 0.13% with Al back electrode

48 It seems that optimal thickness of the single layer OPV is in the range of nm

49 EQE 49 Quinacridone

50 EQE 50 Dimethyl Quinacridone

51 EQE 51 Dichloro Quinacridone

52 Benchmarking H-bonded pigment stability with conjugated Organic Semiconductors E. D. Glowacki et al., Adv. Mat. 25, 1563 (2013)

53 2,620, USD/kg!!!!!!!!

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55 Low price, low toxicity and wide availability Quinacridone Industrial synthesis route Retail price in China: ~ 0.15 USD / Kg (for purchases exceeding 1 ton)

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62 62 Controlling molecular orientation and stacking unpolar polar Orientation and stacking is crucially important for charge transport in H- bonded pigments and depends on dielectric surface properties

63 Conclusions 63 Homojunctions photovoltaics were demonstrated for several Quinacridones and Anthraquinones PCE is ~ 0.1% for vacuum processed and % for solution processed quinacridones Ideal thickness of the homojunctions is in the range of nm

64 PV-Conclusions 64 Every PV technology faces issues and challenges Organic or mixed Organic/Inorganic technology is sharply rising Most likely the Perovskyte technology will become disruptive for classic inorganic PV Still the PV technology will provide only 50% of the answer the remaining 50% is how to store the charges overnight