Presentation is loading. Please wait.

Presentation is loading. Please wait.

IMPROVING EFFICIENCY OF ORGANIC PHOTOVOLTAICS

Similar presentations


Presentation on theme: "IMPROVING EFFICIENCY OF ORGANIC PHOTOVOLTAICS"— Presentation transcript:

1 IMPROVING EFFICIENCY OF ORGANIC PHOTOVOLTAICS
Nanjia Zhou Northwestern University introduce thx u for coming not easy to find a good time in busy march Fortunate to have it this afternoon to spend an hour together make your time worth 11/08/12

2 Nanjia Zhou 1 introduce thx u for coming
not easy to find a good time in busy march Fortunate to have it this afternoon to spend an hour together make your time worth Nanjia Zhou Chang/Marks Group

3 Nanjia Zhou 2 International Energy Outlook 2011 introduce
thx u for coming not easy to find a good time in busy march Fortunate to have it this afternoon to spend an hour together make your time worth Nanjia Zhou Chang/Marks Group International Energy Outlook 2011

4 International Energy Outlook 2011
3 introduce thx u for coming not easy to find a good time in busy march Fortunate to have it this afternoon to spend an hour together make your time worth 03/23/2012 International Energy Outlook 2011

5 Reduced dependence on Fossil Fuels Distributed generation
4 Clean, renewable Reduced dependence on Fossil Fuels Distributed generation Proven, reliable Modularity and Scalability introduce thx u for coming not easy to find a good time in busy march Fortunate to have it this afternoon to spend an hour together make your time worth Photo courtesy: NREL 03/23/2012 Department of Materials Science

6 Nanjia Zhou 5 Photo courtesy: NREL
introduce thx u for coming not easy to find a good time in busy march Fortunate to have it this afternoon to spend an hour together make your time worth Photo courtesy: NREL Nanjia Zhou Chang/Marks Group

7 Nanjia Zhou 6 Photo courtesy: NREL
introduce thx u for coming not easy to find a good time in busy march Fortunate to have it this afternoon to spend an hour together make your time worth Photo courtesy: NREL Nanjia Zhou Chang/Marks Group National Renewable Energy Laboratory (NREL)

8 Mitsubishi Chemical announced a certified 10.0% cell
7 Mitsubishi Chemical announced a certified 10.0% cell introduce thx u for coming not easy to find a good time in busy march Fortunate to have it this afternoon to spend an hour together make your time worth Photo courtesy: NREL Nanjia Zhou Chang/Marks Group National Renewable Energy Laboratory (NREL)

9 Nanjia Zhou 8 Photo courtesy: NREL introduce thx u for coming
not easy to find a good time in busy march Fortunate to have it this afternoon to spend an hour together make your time worth Photo courtesy: NREL Nanjia Zhou Chang/Marks Group

10 Department of Materials Science
9 introduce thx u for coming not easy to find a good time in busy march Fortunate to have it this afternoon to spend an hour together make your time worth Photo courtesy: NREL 03/23/2012 Department of Materials Science

11 Nanjia Zhou The Nobel Prize in Chemistry 2000
10 Alan J. Heeger, Alan G. MacDiarmid and Hideki Shirakawa "for the discovery and development of conductive polymers". introduce thx u for coming not easy to find a good time in busy march Fortunate to have it this afternoon to spend an hour together make your time worth Photo courtesy: NREL Nanjia Zhou Chang/Marks Group

12 Nanjia Zhou Common conducting polymers Soliton Polaron Bipolaron 11
introduce thx u for coming not easy to find a good time in busy march Fortunate to have it this afternoon to spend an hour together make your time worth Polaron Bipolaron Nanjia Zhou Chang/Marks Group

13 1. Organic Field Effect Transistor (OFET)
12 1. Organic Field Effect Transistor (OFET) Source Drain Organic layer + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + Insulating layer - - - - - - - - - - - - - - - - - - - introduce thx u for coming not easy to find a good time in busy march Fortunate to have it this afternoon to spend an hour together make your time worth Gate -30V Nanjia Zhou Chang/Marks Group

14 1. OFET Nanjia Zhou 13 introduce thx u for coming
not easy to find a good time in busy march Fortunate to have it this afternoon to spend an hour together make your time worth Nanjia Zhou Chang/Marks Group

15 1. OFET Nanjia Zhou Photo courtesy: NREL 14 introduce thx u for coming
not easy to find a good time in busy march Fortunate to have it this afternoon to spend an hour together make your time worth Photo courtesy: NREL Nanjia Zhou Chang/Marks Group

16 2. Organic Light Emitting Diode (OLED)
15 2. Organic Light Emitting Diode (OLED) 07 08 09 10 ’’ WXGA 21-23’’ UXGA 40’’/42’’ Full HD 3.5’’ WQVGA*3D 4.8’’ WVGA 7.0’’ WSVGA 4.1’’ WQVGA introduce thx u for coming not easy to find a good time in busy march Fortunate to have it this afternoon to spend an hour together make your time worth 2.0,2.2,2.4,2.6’’ QVGA 2.5’’ QVGA(Landscape) 2.6,2.8,3.0’’ LQVGA 3.1’’ WVGA Nanjia Zhou Chang/Marks Group

17 2. OLED Nanjia Zhou 1. Brighter, thinner, lighter, faster
16 2. OLED 1. Brighter, thinner, lighter, faster 2. Bright from all viewing angles 3. Need less power to run 4. A lot cheaper to produce 5. Expanding memory capability - coating new layer on top of existing one 6. Wider temperature range introduce thx u for coming not easy to find a good time in busy march Fortunate to have it this afternoon to spend an hour together make your time worth OLED is a display device that sandwiches carbon based films between the two electrodes and when voltage is applied creates light. Nanjia Zhou Chang/Marks Group

18 2. OLED Nanjia Zhou 17 introduce thx u for coming
not easy to find a good time in busy march Fortunate to have it this afternoon to spend an hour together make your time worth Nanjia Zhou Chang/Marks Group

19 3. OPV Nanjia Zhou 18 introduce thx u for coming
not easy to find a good time in busy march Fortunate to have it this afternoon to spend an hour together make your time worth Nanjia Zhou Chang/Marks Group

20 3. OPV Nanjia Zhou 19 introduce thx u for coming
not easy to find a good time in busy march Fortunate to have it this afternoon to spend an hour together make your time worth Nanjia Zhou Chang/Marks Group Holger Spanggaard, Frederik C. Krebs, Solar Energy Materials and Solar Cells, Volume 83, Issues 2–3, 15 June 2004, Pages

21 OPV vs. Silicon Cell Nanjia Zhou Photo courtesy: NREL 20 introduce
thx u for coming not easy to find a good time in busy march Fortunate to have it this afternoon to spend an hour together make your time worth Photo courtesy: NREL Nanjia Zhou Chang/Marks Group Harvard Science in the News: https://sitn.hms.harvard.edu/sitnflash_wp/2012/03/issue113/

22 OPV vs. Silicon Cell Nanjia Zhou
21 OPV vs. Silicon Cell Narrower absorption range than silicon cell Lower current output Donor: Electron rich material Acceptor: Electron poor material Bulk Heterojunction: Blend of D/A materials forming a heterogeneous mixture Domain size introduce thx u for coming not easy to find a good time in busy march Fortunate to have it this afternoon to spend an hour together make your time worth Nanjia Zhou Chang/Marks Group Li et al. Nature Photonics 6, 153–161, (2012)

23 Characterization Nanjia Zhou Short circuit Open circuit Forward bias
22 Characterization introduce thx u for coming not easy to find a good time in busy march Fortunate to have it this afternoon to spend an hour together make your time worth Short circuit Open circuit Forward bias Reverse bias Nanjia Zhou Chang/Marks Group Kietzke, Advances in OptoElectronics Volume 2007 (2007), Article ID 40285

24 NU Characterization Nanjia Zhou Class A Solar Cell Analyzer
23 NU Characterization Class A Solar Cell Analyzer AM 1.5G simulated light Scan area: 5 x 5 cm Light and dark evaluation Series resistance evaluation Xenon lamp with an adjustable intensity of W/m2 Calibrated with KG3-filtered Si standard from NREL. Spectral mismatch = 1.00 Spectral Response Examines wavelengths from nm Includes 15 filters in this range Circulating Bath Cell test temperature variable from -15C to +75C introduce thx u for coming not easy to find a good time in busy march Fortunate to have it this afternoon to spend an hour together make your time worth Nanjia Zhou Chang/Marks Group

25 ORGANIC PHOTOVOLTAICS
24 ORGANIC PHOTOVOLTAICS Cathode – Conventional cell Low work function metal: Ca/Al (Anode – Inverted Cell High work function metal: Ag/Au) Cathode IFL – LiF, n-type semiconductors: ZnO, TiO2 Active Layer: blend of donor and acceptor materials Anode IFL: PEDOT:PSS P-type semiconductor: NiO, WO3, MoO3, V2O5 graphene oxide Transparent conductive substrate – ITO, Carbon based material Device used in the lab break down each layer Metal electrode, for conv. Cathode Explain using conv. device Nanjia Zhou Chang/Marks Group

26 ORGANIC PHOTOVOLTAICS
25 ORGANIC PHOTOVOLTAICS μED μCT μCC start my talk from the basic OPV band alignment diagram Nanjia Zhou Chang/Marks Group

27 ORGANIC PHOTOVOLTAICS
26 ORGANIC PHOTOVOLTAICS STRATEGIES FOR EFFICIENCY ENHANCEMENT Ordered Heterojunction: Donor/acceptor form interdigitated morphology within nanometer scale Direct pathways of donor/acceptor to electrodes Photon Management: Alter device architecture to focus photo absorption in active layer Potentially reduce active layer thickness for higher IQE Morphology Control: Domain sizes comparable to exciton diffusion length Efficient carrier transport Experimentally: solvent, additive, processing conditions, and self organizing properties of materials Band Gap Tuning: Lower band gap to raise Jsc. Higher IP polymers and lower EA acceptors to reduce energy loss during charge separation. Decrease LUMO-LUMO offset Most importantly coming from band gap tuning high jsc coming from smaller band gap high voc maintained through low homo Control morphology for efficient excition diffusion and carrier transport Further optimization coming from device architecture Nelson, J. Materials Today 2011, 14, 462–470. Li, G.; Zhu, R.; Yang, Y. 2012, 1–9. Kang, M.-G.; Xu, T.; Park, H. J.; Luo, X.; Guo, L. J. Adv. Mater. 2010, 22, 4378. Nanjia Zhou Chang/Marks Group

28 RESEARCH OUTLINE Morphology Control Band Gap Tuning Photon Management
27 RESEARCH OUTLINE Morphology Control Band Gap Tuning Photon Management Novel Device Architecture Processing conditions; Solvent choice; Polymer stacking; Characterization Morphology-Carrier Transport Relationship Novel high efficiency donor-type polymers, study of device characteristics Materials Development Nanoscale patterning of polymer active layer surface. Photonic and plasmonic enhancement of photocurrent Plasmonic Structure Tandem device to enhance light harvesting; Optimize electron/hole transport Nanowire, Tandem, Hybrid, etc. 1.working w/ synthetic chemist and developed a series of… one work use Bithiophene imide, excellent performance and high Voc 2. relationship between morphology (domain sizes) w/ transport/recombination properties and device performance 3. simple method converting Ag electrode to photo/plas geometry 4. design of ordered heterojunction device using vertically aligned ordered nanowire electrode Nanjia Zhou Chang/Marks Group

29 Morphology Carrier Transport Relationship
Control of nanoscale morphology: Domain size variation Morphology Carrier Transport Relationship Nanjia Zhou Chang/Marks Group

30 28 BILAYER VS. BHJ Nanjia Zhou Chang/Marks Group

31 EFFECT OF PROCESSING CONDITIONS
29 EFFECT OF PROCESSING CONDITIONS Annealing Treat, N. D., Brady, M. A., Smith, G., Toney, M. F., Kramer, E. J., Hawker, C. J. and Chabinyc, M. L. (2011), Interdiffusion of PCBM and P3HT Reveals Miscibility in a Photovoltaically Active Blend. Adv. Energy Mater., 1: 82–89. doi: /aenm Nanjia Zhou Chang/Marks Group

32 EFFECT OF PROCESSING CONDITIONS
30 EFFECT OF PROCESSING CONDITIONS Solvent choice Nanjia Zhou Chang/Marks Group Lee et al. J. Am. Chem. Soc. 130, 3619 (2008)

33 CRYSTALLINITY AND PACKING
31 CRYSTALLINITY AND PACKING Nanjia Zhou Chang/Marks Group Huang et al. J. Phys. Chem. C, 2012, 116 (18), pp 10238–10244

34 CHARACTERIZATION Nanjia Zhou Atomic Force Microscope (AFM),
32 CHARACTERIZATION Atomic Force Microscope (AFM), Transmission Electron Microscope (TEM) Grazing Incidence Wide Angle X-ray Scattering (GIWAXS) Nanjia Zhou Chang/Marks Group Lu et al. Nature Communications 3, Article number: 795

35 PRECISE MANIPULATION OF DOMAIN SIZES
33 PRECISE MANIPULATION OF DOMAIN SIZES High sensitivity of DIO PC71BM BTIBDT Increase DIO concentration 0.5% 1.0% 3.0% 10.0% Nanjia Zhou Chang/Marks Group N. Zhou, A. Guerrero, H. Heitzer, S. Lou et. al.

36 High Performance Donor Materials
Nanjia Zhou Chang/Marks Group

37 Nanjia Zhou 34 Li et al. Nature Photonics 6, 153–161, (2012)
copolymerizing with different donor groups 2 focus on Nanjia Zhou Chang/Marks Group Li et al. Nature Photonics 6, 153–161, (2012)

38 BTIBDT BASED COPOLYMERS
35 BTIBDT BASED COPOLYMERS R1=2-hexyldecyl, R2=2-ethylhexyl; PCE=3.4% R1=2-butyloctyl, R2=2-ethylhexyl; PCE=4.8% R1=2-hexyldecyl, R2=n-dodecyl; PCE=5.5% R1=2-butyloctyl, R2=n-decyl; PCE=3.3% R1=n-octyl, R2=2-butyloctyl; PCE=1.6% copolymerizing with different donor groups 2 focus on Nanjia Zhou Chang/Marks Group Zhou et al. Adv. Mater., 24: 2242–2248

39 BTIBDT BASED COPOLYMERS
36 BTIBDT BASED COPOLYMERS Bithiophene Imide (BTI) and Benzodithiophene (BDT) Copolymers Inverted OPVs The electron deficiency of the BTI units leads to polymers with a low-lying HOMOs (~-5.6 eV). Inverted solar cells are fabricated to investigate the OPV performance of the BTI- based polymers and achieve power conversion efficiencies up to 5.5%, with substantial Vocs above 0.9 V which are among the highest Vocs reported to date for polymer/PCBM solar cells. before making device, promising band alignment and coplanar geometry for pi-pi stacking absorption similar to P3HT, but low HOMO, expect a similar Jsc but hopefully a greater Voc Nanjia Zhou Chang/Marks Group Zhou et al. Adv. Mater., 24: 2242–2248

40 BTIBDT BASED COPOLYMERS
37 BTIBDT BASED COPOLYMERS Bithiophene Imide (BTI) and Benzodithiophene (BDT) Copolymers Inverted OPVs Inverted architectures: ITO/ZnO/polymer:PC71BM/MoOx/Ag Inverted structures avoid oxidation of low work- function cathodes, such as Al or Ca, and acidic PEDOT:PSS etching of ITO, both of which limit conventional devices. ZnO is an excellent cathode interfacial layer due to its high electron mobility, excellent thermal stability, and hole-blocking properties. MoOx conduction band (-2.60 eV) lies sufficiently above the donor LUMOs (-3.7 eV, estimated from the HOMOs and optical band gaps), to block electrons, while the low work function (-5.6 eV) forms a good anode contact with the donor polymers Inverted device used conventional not as efficient reason discussed in paper: low HOMO of polymer 5.6 likely show a mismatch with PEDOT HOMO 5 not the case for MoOx Nanjia Zhou Chang/Marks Group Zhou et al. Adv. Mater., 24: 2242–2248

41 BTIBDT BASED COPOLYMERS
38 BTIBDT BASED COPOLYMERS Device Performance Stability J-V Curve EQE and UV-vis Stability Polymer:PC71BM Solvent Thickness (nm) Voc (V) Jsc (mA/cm2) FF (%) PCE (%) P1 1:1.5 DCB 95 0.992 4.16 47.9 1.98 P2 1:1 100 0.940 4.76 56.3 2.52 DCB+DIOa 0.876 9.69 51.8 4.39 0.922 9.62 62.0 5.50 Best device achieved without thermal annealing Initial drop due to microstructural reorganization Nanjia Zhou Chang/Marks Group Zhou et al. Adv. Mater., 24: 2242–2248

42 BTIBDT BASED COPOLYMERS
39 BTIBDT BASED COPOLYMERS Conventional Device and SCLC measurement Conventional Device Performance Polymer:PC71BM Voc [V] Jsc [mA/cm2] FF (%) PCE (%) P1 1:1.5 0.872 7.87 51.1 3.51 P2 1:1 0.905 8.06 55.1 4.02 Space charged limited current (SCLC) measurement ITO/PEDOT:PSS/polymer/Au Hole mobilities OTFT: 1.2 × 10-4 and 2.8 × 10-4 cm2V-1s-1 SCLC: 5.5 × 10-5 and 1.9 × 10-4 cm2V-1s-1 for P1 and P2-based OTFTs and hole only devices, respectively Nanjia Zhou Chang/Marks Group Zhou et al. Adv. Mater., 24: 2242–2248

43 BTIBDT BASED COPOLYMERS
40 BTIBDT BASED COPOLYMERS Morphology Optimization Without DIO, predominantly phase-segregated morphologies for the P1/PC71BM and P2/PC71BM blends. The dark regions in the TEM images confirm large PC71BM domain sizes -- far larger than typical exciton diffusion lengths (~10 nm). Consequently, poor exciton dissociation and low current density are expected. Significantly more homogeneous morphologies are found for P1/PC71BM and P2/PC71BM films processed with DIO. nanosacle phase separation and bicontinuous interpenetrating networks result in more efficient charge separation and transport, leading to more than doubled Jsc. Nanjia Zhou Chang/Marks Group Zhou et al. Adv. Mater., 24: 2242–2248

44 BTIDTS BASED COPOLYMERS
41 BTIDTS BASED COPOLYMERS BTI and Dithienosilole (DTS) Copolymers Inverted OPVs Polymer DCB:DIO (%:%) Voc (V) Jsc (mA/cm2) FF (%) PCE (%) P1 100:0 0.838 6.06 52.6 2.67 98:2 0.834 12.51 53.1 5.54 P2 0.847 6.46 48.4 2.65 0.803 12.81 62.3 6.41 Nanjia Zhou Chang/Marks Group X. Guo, N. Zhou, et al. JACS (2012)

45 BTI BASED COPOLYMERS Nanjia Zhou 42
Chang/Marks Group X. Guo, N. Zhou, et al. JACS (2012)

46 BTI BASED COPOLYMERS Nanjia Zhou 43
Chang/Marks Group X. Guo, N. Zhou, et al. JACS (2012)

47 BTI BASED COPOLYMERS Nanjia Zhou 44
Chang/Marks Group X. Guo, N. Zhou, et al. JACS (2012)

48 BTIDTG COPOLYMERS Nanjia Zhou 45 Polymer % of DIO additives Voc (V)
Jsc (mA/cm2) FF (%) PCE (%) PBTISi-C6 2.0 0.824 12.59 60.6 6.29 PBTISi-C8 0.803 12.81 62.3 6.41 PBTISi-EH 0.791 12.49 56.4 5.57 PBTIGe-C6 3.0 0.770 11.76 47.2 4.27 Nanjia Zhou Chang/Marks Group X. Guo, N. Zhou, et al. JACS (2012)

49 BTI/TPD-DTS COPOLYMERS
46 BTI/TPD-DTS COPOLYMERS Nanjia Zhou Chang/Marks Group X. Guo, N. Zhou, et al. JACS (2012)

50 BTIDTS BASED COPOLYMERS
48 BTIDTS BASED COPOLYMERS BTI and Dithienosilole (DTS) Copolymers Inverted OPVs polymer/PC71BM DCB:DIO=100:0 polymer/PC71BM DCB:DIO=98:2 neat polymer P1 P2 π-π stacking distances are 3.6 Å and 3.5 Å for P1 and P2, respectively Nanjia Zhou Chang/Marks Group X. Guo, N. Zhou, et al. JACS (2012)

51 BTIDTS BASED COPOLYMERS
49 BTIDTS BASED COPOLYMERS Nanjia Zhou Chang/Marks Group X. Guo, N. Zhou, et al. JACS (2012)

52 BTIDTS MORPHOLOGY Nanjia Zhou
50 BTIDTS MORPHOLOGY TEM images of PBTISi-C8 with different D/A ratio: (a) P:PC71BM (1:1), (b) P:PC71BM (1:1.5), and (c) P:PC71BM (1:2) blend films processed in DCB as solvent with 2% DIO. Nanjia Zhou Chang/Marks Group X. Guo, N. Zhou, et al. JACS (2012)

53 BTIDTG COPOLYMERS Nanjia Zhou 51 X. Guo, N. Zhou, et al. JACS (2012)
Chang/Marks Group X. Guo, N. Zhou, et al. JACS (2012)

54 HiGH FF OPV AND MORPHOLOGY STUDY
52 HiGH FF OPV AND MORPHOLOGY STUDY Nanjia Zhou Chang/Marks Group X. Guo, N. Zhou, et al. Nature Photonics (2012)

55 HiGH FF OPV AND MORPHOLOGY STUDY
53 HiGH FF OPV AND MORPHOLOGY STUDY Nanjia Zhou Chang/Marks Group X. Guo, N. Zhou, et al. Nature Photonics (2012)

56 HiGH FF OPV AND MORPHOLOGY STUDY
54 HiGH FF OPV AND MORPHOLOGY STUDY Nanjia Zhou Chang/Marks Group X. Guo, N. Zhou, et al. Nature Photonics (2012)

57 HiGH FF OPV AND MORPHOLOGY STUDY
55 HiGH FF OPV AND MORPHOLOGY STUDY Nanjia Zhou Chang/Marks Group X. Guo, N. Zhou, et al. Nature Photonics (2012)

58 Nanoscale patterning of polymer active layer surface.
Photonic and plasmonic enhancement of photocurrent Photon Management Nanjia Zhou Chang/Marks Group

59 PLASMONIC OPV Nanjia Zhou Device Fabrication Enhancement at
56 PLASMONIC OPV Ag nanowire grating as electrode blending Au nanoparticle into interfacial layer metallic nanoparticles at front electrode Device Fabrication Enhancement at Front electrode M. Heo, H. Cho, J. Jung, J. Jeong, S. Park, J. Kim, Adv. Mater. 2011, 23, 5689 M. Kang , T. Xu , H. Park , X. Luo , L.J. Guo Adv. Mater. 2010, 22, 4378 J. Yang, J. You, C. Chen, W. Hsu, H. Tan, X. Zhang, Z. Hong, Y. Yang ACS Nano 2011 5 (8), 6210 Nanjia Zhou Chang/Marks Group

60 PLASMONIC OPV Device Fabrication Modifying Front Electrode
57 PLASMONIC OPV Device Fabrication Modifying Front Electrode Modifying Rear Electrode Lower transmission at TCO Reducing conductivity of TCO Disrupting organic/inorganic interface at TCO Affecting film quality and possibly polymer packing Introducing extra step that cannot be easily incorporated into fabrication, thus affect reproducibility. No effect on device fabrication prior to metal evaporation Easily convert the metallic electrode into a plasmonic grating. The grating can increase the amount of light trapped in the active layer through three potential pathways. Trap the light in the form of surface plasmon polaritons (SPP). Increase the surface area of the interface. Increase the diffraction of light. Nanjia Zhou Chang/Marks Group

61 PLASMONIC OPV Nanjia Zhou ITO ZnO Active Layer MoOx Ag ITO
58 PLASMONIC OPV Device Fabrication ITO ZnO Active Layer MoOx Ag ITO ZnO solution processing Active layer Hot embossing Thermal evaporation of rear electrode Collaboration with S. Lubin (Odom group), A. Hryn (Odom group) Nanjia Zhou Chang/Marks Group N. Zhou, S. Lubin, A. Hryn, X. Guo et. al. Manuscript in preparation

62 PLASMONIC OPV Nanjia Zhou Device Performance 59 Device Voc [V]
Jsc [mA/cm2] FF (%) PCE (%) Plasmonic 0.580 11.5 64.0 4.28 No plasmonic 0.582 9.38 68.5 3.74 Sq 600 nm Sq 400 nm Plasmonic 0.565 12.8 56.2 4.07 Collaboration with S. Lubin (Odom group), A. Hryn (Odom group) Nanjia Zhou Chang/Marks Group N. Zhou, S. Lubin, A. Hryn, X. Guo et. al. Manuscript in preparation

63 Novel Device Architectures
Tandem device to enhance light harvesting; Optimize electron/hole transport Novel Device Architectures Nanjia Zhou Chang/Marks Group

64 TANDEM SOLAR CELLS Nanjia Zhou 60
introduce thx u for coming not easy to find a good time in busy march Fortunate to have it this afternoon to spend an hour together make your time worth Nanjia Zhou Chang/Marks Group Yang Yang et al. Nature Photonics, 6, 2012, 180

65 61 TANDEM SOLAR CELLS The maximum efficiency for a two junction tandem under the AM1.5G spectrum and without concentration is 47 %. At the peak efficiency the top cell has a bandgap of 1.63 eV and the bottom cell has a bandgap of 0.96 eV. Thermal stability Nanjia Zhou Chang/Marks Group

66 TANDEM SOLAR CELLS Nanjia Zhou
62 TANDEM SOLAR CELLS PCE greater than 40% is the highest efficiency obtained to date for triple junction inorganic photovoltaic cells. Thermal stability Nanjia Zhou Chang/Marks Group

67 TANDEM ORGANICS SOLAR CELLS
63 TANDEM ORGANICS SOLAR CELLS Thermal stability P3HT PSBTBT Nanjia Zhou Chang/Marks Group Jin Young Kim, Kwanghee Lee, Nelson E. Coates, Daniel Moses, Thuc-Quyen Nguyen, Mark Dante, and Alan J. Heeger Science 13 July 2007: 317 (5835),

68 TANDEM ORGANICS SOLAR CELLS
64 TANDEM ORGANICS SOLAR CELLS Dresden, Germany-based OPV thin-film developer Heliatek has achieved a new organic tandem solar cell world record with 10.7% cell efficiency on a 1.1cm2 substrate. “Deposition of small organic molecules in a low temperature, roll-to-roll vacuum process” Yang Yang group, UCLA reaches 10.6% efficiency a world’s first for polymer organic photovoltaic devices “Their tandem structure consists of a front cell with a larger (or high) band gap material and a rear cell with a smaller (or low) band gap polymer, connected by a designed interlayer.” Sumitomo's low–band gap polymer Thermal stability Nanjia Zhou Chang/Marks Group

69 INTERLAYER Nanjia Zhou Metal ohmic contacts with sub-cells
65 INTERLAYER Metal ohmic contacts with sub-cells Ag, Au: Yakimov et al. (2002) Colsmann et al. (2006) used n-doped and p-doped organic layers on either side of a thin Au layer as hole blocking and electron blocking layer, respectively. first time reaches nearly additive Voc =1 V p-type layer: high work function metal oxides such as molybdenum oxide (MoO3) or tungsten oxide (WO3), PEDOT:PSS n-type layer: solution-processed ZnO and TiO2 Thermal stability A. Yakimov and S. R. Forrest, Appl. Phys. Lett., 2002, 80, 1667. A. Colsmann, J. Junge, C. Kayser and U. Lemmer, Appl. Phys. Lett., 2006, 89, Nanjia Zhou Chang/Marks Group

70 PROCESSING Nanjia Zhou
66 PROCESSING Sustain the solution process of the top polymer layer and protect the bottom polymer layer deposited ITO or thermally evaporated semitransparent metal layers such as Au An n-type layer using ZnO or TiO2 is coated from an alcohol based solvent aqueous based PEDOT:PSS Difficult to find a solvent for the top polymer layer that does not dissolve the bottom polymer layer. (high boiling point solvents for the top polymer layer may be detrimental to the integrity of underlying layers) Wettability of interlayer and top cells Modified PEDOT:PSS layer (dilute by alcohol, add surfactant) Thin layer of metal Thermal stability Nanjia Zhou Chang/Marks Group

71 Nanjia Zhou 67 Yang Yang et al. Nature Photonics, 6, 2012, 180
Thermal stability Nanjia Zhou Chang/Marks Group Yang Yang et al. Nature Photonics, 6, 2012, 180

72 Nanjia Zhou 68 Thermal stability
Chang/Marks Group N. Zhou, et al. Manuscript in preparation

73 ITO NANOWIRE ELECTRODE
69 ITO NANOWIRE ELECTRODE Surface modification IFL by ALD ITO Vertically grown ITO nanowire on ITO substrate Vertically grown ITO nanowire on ITO substrate SAM growth Li, S. Q.; Guo, P.; Zhang, L.; Zhou, W.; Odom, T. W.; Seideman, T.; Ketterson, J. B.; Chang, R. P. H. ACS Nano 2011, 5, 9161–9170. Electrode deposition Active layer filling Inefficiency of hole transport due to relatively poor hole mobility of polymer semiconductor comparing to the electron mobility of PCBM Reduce hole transport distance Greatly enhance electrode (anode) surface area Potentially increase hole transport and hole collection efficiencies Chang group developed vertically aligned nanowire arrays Rational is to use this electrode for more efficient carrier extraction/reduce transport distance Experimentally to introduce geometry for both electrode But easier to achieve at bottom electrode Filled with active layer Nanjia Zhou Chang/Marks Group N. Zhou, et al. Manuscript in preparation

74 ITO NANOWIRE ELECTRODE
70 ITO NANOWIRE ELECTRODE Current fabricated device structure Proposed device structure Facilitate hole transport Thermal stability Nanjia Zhou Chang/Marks Group N. Zhou, P. Guo, S. Li, et. al.

75 SUMMARY AND OUTLOOK Nanjia Zhou Morphology control
Manipulation of domain (PCBM cluster) size Processing conditions Characterization of domain size Relate to J-V parameters Materials development BTI-BDT demonstrated one of the highest Voc BTI-DTS achieved performance of 6.4% Highest performance in literatures: 8.7% Photon management A simple method through hot embossing Convert the standard Ag electrode >20% increase in Jsc Novel Device Architectures Tandem OPVs Facilitate carrier transport/reduce bimolecular recombination probability Active layer filtration through solution processing/surface functionalization Further optimize processing conditions to create interdigitated structure Nanjia Zhou Chang/Marks Group

76 ACKNOWLEDGEMENT Advisers: Prof. Tobin Marks Prof. RPH Chang
Prof. Antonio Facchetti Committee Members: Prof. Lin Chen Prof. Mark Hersam Marks group Dr. Xugang Guo Mimi Lou Stephen Loser Chang group: Dr. D. B. Buchholz Shiqiang Li Peijun Guo Marks B team members Collaborators: Dr. Antonio Guerrero, Prof. Juan Bisquert group, Spain Steven Lubin and Alex Hryn, Prof. Teri Odom group Nanjia Zhou Chang/Marks Group

77 Thank you! “The Apollo Projects Of Our Time” - Steven Chu
Courtesy of Backwoods Solar Electric Systems & NREL


Download ppt "IMPROVING EFFICIENCY OF ORGANIC PHOTOVOLTAICS"

Similar presentations


Ads by Google