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The Versatility of Mesoscopic Solar Cells.

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Plenary lecture - XV B-MRS Meeting - Campinas, SP, Brazil - September, 25 to 29, 2016.
Author: Anders Hagfeldt (EPFL, Switzerland).

Published in: Science
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The Versatility of Mesoscopic Solar Cells.

  1. 1. B-MRS 2016, Campinas, September 29, 2016 The Versatility of Mesoscopic Solar Cells Anders Hagfeldt Laboratory of Photomolecular Sciences (LSPM) Dyenamo AB www.dyenamo.se Materials, research equipment, consultancy, etc, for solar cells and solar fuels.
  2. 2. Welcome to Lausanne! • Dye-sensitized solar cells • Minimizing internal potential losses • Cu-complex redox species • Perovskite solar cells • Mixed compositions • Planar devices > 20% • The quadrupole • Stable perovskite solar cells • Towards GaAs ?
  3. 3. The Solar Cell Kit
  4. 4. Solar Cells from the Kitchen White pigment TiO2 Dye Blueberry, Tea, Wine ... Cathode: Grafite Electrolyte: Iodide/tri-iodide Electrical contatcs The solar cell drives a simple LCD display
  5. 5. Dye-Sensitization Colour Photography, Erythrosin dye on Ag-halides. J. Moser, Monatsh. Chem. 8 (1887) 373 Mechanism of dye-sensitization. Rose bengal on ZnO. H. Gerischer and H. Tributsch, Ber. Bunsenges. Phys. Chem. 72 (1968) 437. Gerischer, H.; Michel-Beyerle, M. E.; Rebentrost, F.; Tributsch, H. Electrochim. Acta 1968, 13, 1509.
  6. 6. The Quantum Leap of DSSC – a paradigm shift of photovoltaics Nature, 1991, 353, 7377. J. Phys. Chem, 1990, 94, 8720. Olympic Games, Mexico, 1968 From 8.35 m 8.90 mFrom < 1% 7.1% Brian O’Regan and Michael Grätzel HOPV 2012, juanbisquert.wordpress.com Bob Beamon
  7. 7. TiO2 Light e-e- E I- / I3 - e - DyeTCO Electrolyte e - hn e - e - Dye-sensitized Solar Cells DSC Operational Principles
  8. 8. Why are the electrons moving in the right direction? Kinetic model fs ns - ms ns - ms ms e- e- e- Ru N N N N N N C C S S HOOC HOOC COOH COOH + + Excited dye Semiconductor Dye Electrolyte e Charge separation due to the molecular architecture of the dye/oxide interaction
  9. 9. DSC niche applications Vertical – Facades North-West Orientation Intermittent and Diffuse Light Design – Appearance Indoor High Voltage
  10. 10. 10 Industrialization of DSC - status Consumer Electronics - YES Large-scale electricity production – Breakthroughs needed! Requires < 0.5$/Wpeak DSC in buildings – ? Logitech Solaronix will build the glass facade for the new congress building at EPFL
  11. 11. The Hunt for the Half Volt – Limitation with the I-/I3 - redox system E0’(I3 -/I-) = 0.34 V E0’(D+/D) = 1.10 V 0.76 V E0-0 = 1.75 eV EC = -0.5 V VOC = 0.74 V V vs NHE + I2 - / I- A two electron transfer process: How much of the 0,5 - 0,7V can we take out of the system? Need for alternative redox systemsBoschloo, Hagfeldt, Accounts of Chemical Research, 42 (2009) 1819-1826.
  12. 12. In 2010 we introduced the ’marriage’ between a blocking dye and Co-complex redox systems D35 Feldt, Gibson, Gabrielsson, Sun, Boschloo, Hagfeldt, J. Am. Chem. Soc. 2010, 132, 16714. Efficiency of 7% TiO2 Dye Co-complex
  13. 13. Co-sensitization of two organic dyes; ADEKA-1 and LEG4 Cobalt-phenantroline as redox couple Top efficiency: 14.3%
  14. 14. How to improve it? Studies of Driving Force for Regeneration S. .M. Feldt, G. Wang, G. Boschloo, A. Hagfeldt, J. Phys. Chem. C 2011, 115, 21500 Electron transfer studies show that a driving force of 0.4V is necessary for efficient regeneration of the oxidized dye in these systems.
  15. 15. Cu-complexes as redox couple in liquid DSC Copper phenanthroline complexes Cu(I) and Cu(II) Organic dye, LEG4 Marina Freitag et al. J. Phys. Chem. C, DOI: 10.1021/acs.jpcc.6b01658 E0’ Cu(I/II)(dmp)2 = 0.94 V vs SHE Efficient dye regeneration with a driving force of only 0.2V!
  16. 16. Breakthrough using Cu-complex as hole transporter material for solid-state DSC Dried out Cu-complex layer Efficiency of 8.2%. Conventional spiro-OMeTAD gave 5.6%. Marina Freitag et al., Energy & Environ. Sci., 2015, 8, 2634-2637
  17. 17. Several Concepts Based on DSC, some examples - + Photoanode Photocathode Q-dot Solar Cells Dye-sensitized Solar Fuel Solid-state DSC Tandem DSC
  18. 18. Tsutomu (Tom ) Miyasaka playing his violin fabricated in 1835 in Torino Italy during the ICES 2014 conference Dinner in Niseto, Hokkaido, Japan on February 06, 2014. PSCs evolved from the DSC The first embodiment of a PSC described by Miyasaka In his 2009 JACS paper was a mesoscopic dye sensitized solar cell using ammonium lead halide perovskites as sensitizer and iodide base liquid electrolyte.
  19. 19. Chung, I., Lee, B., He, J., Chang, R. P. H. & Kanatzidis, M. G. All-solid-state dye-sensitized solar cells with high efficiency Nature 485, 4478?6?–4?8?9 (2012). Year 2012 Landmark paper for PSCs Electron conduction assumed by CH3NH3PbI3  Hole conduction assumed by PSC H.S.Kim, C.R.Lee, J.H.Im, K.B. Lee, T. Moehl, A. Marchioro, S.J.Moon, R. R.Humphry Baker, J.H.Yum, J.E. Moser, M. Grätzel, N.G. Park, Lead Iodide Perovskite Sensitized All-Solid-State Submicron Thin Film Mesoscopic Solar Cell with Efficiency Exceeding 9%, Sci.Reports 2, 591 2012 Science 2012
  20. 20. CH3NH3PbI3: Ambipolar semiconductor band gap 1.55 eV Bohr radius of the first exciton: 2 nm Exciton binding energy 10 -30 meV, exciton dissociation time 1-2 ps ! Band alignement of pervoskite/TiO2/spiro-MeOTAD heterojunction solar cells
  21. 21. PLETHORA OF PEROVSKITE FILM PREPARATION METHODS Ex. Two-step technique to form the hybrid perovskite :  spin coating  dip coating  chemical vapour deposition  spray pyrolysis J. Burschka et al. Nature, 499, 316-319 (2013)  atomic layer deposition  ink-jet printing  thermal evaporation  etc, …
  22. 22. Several Device Structures and Applications Planar Mesoscopic Inverted • Lasing • Light emitting devices • Tandem solar cells • Photodetectors • XRD-detection • …...
  23. 23. EPFL’s most efficient pervoskite solar cells employ mixtures of organic cations and iodide /bromide as anion General composition FA1-xMAxPb(I1-xBrx) FA = R1 – R4 = H formamidinium MA = methylammonium X = 0.15 gives optimal results N. Pellet et al., Mixed-Organic-Cation Perovskite Photovoltaics for Enhanced Solar -Light Harvesting. Angew. Chem. Int. Ed. 53, 3151-3157 (2014). N. J. Jeon et al., Compositional engineering of perovskite materials for high-performance solar cells. Nat. 517, 476-480 (2015).
  24. 24. Electroluminescent PSCs with PCE = 20.8 based on tailored mixed cation perovskites use stochiometric excess of PbI2 Dongqin Bi, Wolfgang Tress, M. Ibrahim Dar, Peng Gao, Jingshan Luo, Clémentine Renevier, Kurt Schenk, Antonio Abate, Fabrizio Giordano, Juan-Pablo Correa Beana, Jean- David Decoppet, Shaik M. Zakeeruddin, M.Khaja Nazeeruddin, Michael Grätzel and Anders Hagfeldt • Single step from a solution containing a mixture of FAI, PbI2, MABr and PbBr2, solvent DMF:DMSO (vol. 4:1) • Mesoporous TiO2 and spiro-MeOTAD • Molar ratio of PbI2/FAI of 1.05 in the precursor solution. • Excess PbI2 content is about 3 weight %. • Excess of PbI2 suppresses non-radiative charge carrier recombination. • External electroluminescence quantum efficiency 0.5 % at a voltage of 1.5 V • Science Advances 2, (2016) 340
  25. 25. ”During spin-coating we introduce PMMA in a chlorobenzene/toluene mixture to template crystal formation and growth of the perovskite. The PMMA serves as a support to induce nucleation of small perovskite crystals and directs the growth of these crystals.”DOI: 10.1038/NENERGY.2016.142
  26. 26. 0 0.3 mg ml-1 0.6 mg ml-1 1.5 mg ml-1 4.0 mg ml-1 Optimal concentration of PMMA = 0.6 mg ml-1. FTIR: The carbonyl groups in PMMA form an intermediate adduct with PbI2. Retard crystal growth and improve crystallinity. Longer electron lifetimes with PMMA At higher concentrations new particles appear at grain boundaries (PMMA particles?).
  27. 27. Dongqin Bi Certified efficiency at Newport, 21.0%, Dec. 2015 (hysteresis-free) Voc = 1.13 V Jsc = 23.8 mA/cm2 FF = 0.78 PEC = 21.0 % Our Certified Champion Cell Certified world record is 22.1% (March 2016) by Seok et al.
  28. 28. Dr. Xiong Li 2016 Vacuum flash treatment produces smooth and shiny perovskite films of high quality
  29. 29. Successful scale-up of a mesoscopic PSC to 1cm2 size Certified PCE 19.6 % Stabilized power output for best cell with PCE of 20.3 % X. Li, D. Bi, C. Yi, J.-D.Décoppet, J. Luo, S. M. Zakeeruddin, A. Hagfeldt and M.Grätzel* Science, 10.1126/science.aaf8060 (2016)
  30. 30. Cs additive Michael Saliba M. Saliba et al., Energy & Environmental Science, 2016, DOI: 10.1039/C5EE03874J
  31. 31. 2016-03-01 Michael Saliba, Triple Cations for Stability, Reproducibility and High Efficiency (submitted) What happens if caesium (Cs) is added? (Triple cation mixtures) 32 Disappearance of the yellow phase and PbI2 excess 10 20 30 40 50 x = 15% x = 10% x = 5% Intensity(a.u.) 2 (°) x = 0% δ PbI2 10 20 30 40 50 x = 15% x = 10% x = 5% Intensity(a.u.) 2 (°) x = 0% Csx(MA0.17FA0.83)(1-x)Pb(I0.83Br0.17)3 (nominal precursor composition) written as CsxM
  32. 32. 2016-03-01 Michael Saliba, Triple Cations for Stability, Reproducibility and High Efficiency (submitted) Devices cross sectional SEM 33 Cs0M Cs5M Cs5M • More monolithically grown crystals (not seen before for MA/FA) Cs5M M. Saliba et al., Cesium-containing Triple Cation Perovskite Solar Cells: Improved Stability, Reproducibility and High Efficiency, Energy & Environmental Science, 2016, DOI: 10.1039/C5EE03874J
  33. 33. Triple cation perovskites and stability Cs+ stabilizes the power output in full sunlight over hundreds of hours Small initial PCE decline Is reversible What happens at higher temperatures?
  34. 34. Planar PSC Structures Using ALD SnO2 Dr. Ludmilla Steier Dr. Juan-Pablo Correa-Baena Flat SnO2 ALD layer works better than flat TiO2 ALD Layer - Band Alignment Engineering hole transporter Perovskite electron transporter Planar devices! J.-P. Correa Baena, L. Steier et al. Energy Environ. Sci. DOI: 10.1039/C5EE02608C Stranks, NNANO (2015) TiO2 SnO2 X Perovskite Perovskite HTL Au
  35. 35. 36
  36. 36. 37 New Solution-Processed Method for SnO2 deposition No need of an ALD as in our previous study, while achieving similar results Anaraki, E. H.; Kermanpur, A.; Steier, L.; Domanski, K.; Matsui, T.; Tress, W.; Saliba, M.; Abate, A.; Gratzel, M.; Hagfeldt, A.; Correa-Baena, J.-P., Energy & Environmental Science 2016. DOI: 10.1039/C6EE02390H -25 -20 SnO2 Perovskite 70℃ 180℃ Chemical Bath Deposition Perovskite: Triple cation protocol
  37. 37. 38 Yields High Efficiencies PCEs = 20.8% 0.0 0.2 0.4 0.6 0.8 1.0 1.2 -25 -20 -15 -10 -5 0 Voltage / V J/mA×cm-2 SC-CB 0 20 40 60 0 10 20 Time / s PCE/% Anaraki, E. H.; Kermanpur, A.; Steier, L.; Domanski, K.; Matsui, T.; Tress, W.; Saliba, M.; Abate, A.; Gratzel, M.; Hagfeldt, A.; Correa-Baena, J.-P., Energy & Environmental Science 2016. DOI: 10.1039/C6EE02390H Best Voc = 1.21 V at Eg = 1.62 eV. Close to thermodynamic limit of 1.32 V!
  38. 38. 2016-09-13, Michael Saliba, Multication perovskites Device results – New system M. Saliba, T. Matsui, K. Domanski, J.-Y. Seo, A. Ummadisingu, S. M. Zakeeruddin, J. P. Correa-Baena, W. R. Tress, A. Abate, A. Hagfeldt, M. Grätzel Science I, online, Thursday Sept. 29
  39. 39. 40 Device results • Highest PCE: 21.6% stabilized • Voc is 1240mV (band gap: 1.63 eV) Close to theoretical limit • Among lowest loss-in-potentials (for any PV material) • Perovskites close to GaAs! • Exceptional electroluminescence • 4% EQE: almost as high as pLEDs
  40. 40. 41 Industrial norms that must be fulfilled for perovskites to go commercial: • 85C in the dark for 1000h (<10% degradation to pass tests!) • 60C under full illumination and load for 1000h Problem: • Au migration into perovskite Solutions: • Cr buffer layer • Polymeric HTMs can hinder gold migration But is it stable? ACS Nano DOI: 10.1021/acs.nano.6b02613
  41. 41. Stability tests Stability: 95% is retained after 500h of continous operation (MPP) at 85 oC and full illumination Achilles‘ heel is not perovskite but rather Au migration • Compounded stress test: 85C, full illumination, MPP for 500h (in N2 atmosphere) • Polymer as HTM • Starting efficiency of device: > 17%
  42. 42. First 3 months, Ar atmosphere. Next 3 months under air at 50% R, In both cases under continuous UV irradiation Terrace of the Politecnico di Torino from October to December 2015 Encapsulated Cells Science II, online, Thursday Sept. 29 Federico Bella*, Gianmarco Griffini, Juan-Pablo Correa-Baena*, Guido Saracco, Michael Grätzel, Anders Hagfeldt, Stefano Turri, Claudio Gerbaldi
  43. 43. For our best Voc we loose 90 mV with an ERE of 1% (at Jsc injected currents) – Better than the best Si cells! Towards GaAs?
  44. 44. The EPFL team Michael Grätzel LSPM Dongqin Bi Juan Pablo Correa-Baena Marina Freitag Somayyeh Gholipour Elham Halvani Anaraki Jeannette Kadro Medina Kazuteru Nonomura Pan Linfeng Yasemin Saygili Nick Vlachopoulos LPI Shaik M. Zakeeruddin Wolfgang Tress Michael Saliba Konrad Domanski Antonio Abate Xiong Li Chenyi Yi ….

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