Inverted non-fullerene organic solar cells: Charge carrier extraction and interface characterization

• Applicants: Dr. Thomas Mayer; Professor Dr. Thomas Riedl
• Subject Area: Experimental Condensed Matter Physics ; Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering
• Term: from 2012 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 196886395

• Final Report Year: 2022

Final Report Abstract

The aim of this research project was to gain a fundamental understanding of charge extraction via dedicated oxide interlayers in inverted organic solar cells (OSCs). To this end, in a close collaboration of the research teams at University of Wuppertal and TU Darmstadt we combined the study of the electro-optic device characteristics and photoelectron spectroscopy (PES) of the relevant organic/oxide interfaces. Our project was mainly focused on the electron extraction at the cathode (bottom) side of inverted OSCs. In the beginning of this project OSCs were almost exclusively based on fullerenes as acceptors, however we also considered non-fullerene acceptors in the last stage of our project. We initially studied the common phenomenon of light soaking in OSCs incorporating metal-oxide electron extraction layers (EEL), such as TiOx or ZnO. We were able to rule out a barrier at the interface ITO/TiOx and a potentially low bulk conductivity of TiOx as origin of the s-shaped J/V characteristics upon illumination without UV spectral components. Using a correlation of device data and photoelectron spectroscopy we were able to identify an extraction barrier between metal-oxide and fullerene. UV light soaking of the TiOx/organic acceptor interface reduced the barrier and improved electron extraction. We could also show that for the electrically doped Al:ZnO instead of TiOx no barrier is formed and UV light soaking is not required. As an alternative to electrical doping, we have identified plasmonic sensitization of metal-oxides by the introduction of metal-nanoparticles as an approach to mitigate the need for UV activation. Plasmonically mediated charge transfer from the metal nanoparticles to the metal-oxide already occurs upon illumination with hν

Publications

• Room-temperature solution processed SnOx as electron extraction layer for inverted organic solar cells with superior thermal stability, J. Mater. Chem. 22, 16224 (2012)
  S. Trost, K. Zilberberg, A. Behrendt, and T. Riedl
  (See online at https://doi.org/10.1039/c2jm33445c)
• Transition Metal Oxides for Organic Electronics: Energetics, Device Physics and Applications, Adv. Mater. 24, 5408 (2012)
  J. Meyer, S. Hamwi, M. Kröger, W. Kowalsky, T. Riedl, and A. Kahn
  (See online at https://doi.org/10.1002/adma.201201630)
• Energy Band Alignment between Anatase and Rutile TiO2. Journal of Physical Chemistry Letters, 4(23): p. 4182-4187 (2013)
  V. Pfeifer, P. Erhart, S. Li, K. Rachut, J. Morasch, J. Broetz, P. Reckers, T. Mayer, S. Ruehle, A. Zaban, I. Mora Sero, J. Bisquert, W. Jaegermann, and A. Klein
  (See online at https://doi.org/10.1021/jz402165b)
• Overcoming the “light-soaking” issue in inverted organic solar cells by the use of Al:ZnO electron extraction layers, Adv. Energy Mater. 3, 1437 (2013)
  S. Trost, K. Zilberberg, A. Behrendt, A. Polywka, P. Görrn, P. Reckers, J. Maibach, T. Mayer, T. Riedl
  (See online at https://doi.org/10.1002/aenm.201300402)
• Solution Processed Metal-Oxides for Organic Electronic Devices, J. Mater. Chem. C 1, 4796 (2013)
  K. Zilberberg, J. Meyer, and T. Riedl
  
• Deep and shallow TiO2 gap states on cleaved anatase single crystal (101) surfaces, nanocrystalline anatase films, and ALD titania ante and post annealing, J. Phys. Chem C 119, 9890 (2015)
  P. Reckers, M. Dimamay, J. Klett, S. Trost, K. Zilberberg, T. Riedl, B. Parkinson, J. Brötz, W. Jaegermann, and T. Mayer
  (See online at https://doi.org/10.1021/acs.jpcc.5b01264)
• Plasmonically sensitized metal-oxide electron extraction layers for organic solar cells, Sci. Rep. 5, 7765 (2015)
  S. Trost, T. Becker, K. Zilberberg, A. Behrendt, A. Polywka, R. Heiderhoff, P. Görrn, and T. Riedl
  (See online at https://doi.org/10.1038/srep07765)
• Tin Oxide (SnOx) as Universal “Light-Soaking” Free Electron Extraction Material for Organic Solar Cells, Adv. Energy Mater. 5, 1500277 (2015)
  S. Trost, A. Behrendt, T. Becker, A. Polywka, P. Görrn, and T. Riedl
  (See online at https://doi.org/10.1002/aenm.201500277)
• Avoiding Photoinduced Shunts in Organic Solar Cells by the Use of Tin Oxide (SnOx) as Electron Extraction Material Instead of ZnO, Adv. Energy Mater. 6, 1600347 (2016)
  S. Trost, T. Becker, A. Polywka, P. Görrn, M. F. Oszajca, N. A. Luechinger, D. Rogalla, M. Weidner, P. Reckers, T. Mayer, and T. Riedl
  (See online at https://doi.org/10.1002/aenm.201600347)
• Indium-Free Perovskite Solar Cells Enabled by Impermeable Tin-Oxide Electron Extraction Layers, Adv. Mater. 29, 1606656 (2017)
  T. Hu, T. Becker, N. Pourdavoud, J. Zhao, K. Brinkmann, R. Heiderhoff, T. Gahlmann, Z. Huang, S. Olthof, K. Meerholz, D. Többens, B. Cheng, Y. Chen, and T. Riedl
  (See online at https://doi.org/10.1002/adma.201606656)
• Self-Encapsulating Thermostable and Air- Resilient Semitransparent Perovskite Solar Cells, Adv. Energy Mater. 7, 1602599 (2017)
  J. Zhao, K. Brinkmann, T. Hu, N. Pourdavoud, T. Becker, T. Gahlmann, R. Heiderhoff, A. Polywka, P. Görrn, Y. Chen, B. Cheng, and T. Riedl
  (See online at https://doi.org/10.1002/aenm.201602599)
• Suppressed decomposition of organo-metal halide perovskites by impermeable electron extraction layers in inverted solar cells, Nature Communications 7, 13938 (2017)
  K. Brinkmann, J. Zhao, N. Pourdavoud, T. Becker, T. Hu, S. Olthof, K. Meerholz, L. Hoffmann, T. Gahlmann, R. Heiderhoff, M. F. Oszajca, N. A. Luechinger, D. Rogalla, Y. Chen, B. Cheng, and T. Riedl
  (See online at https://doi.org/10.1038/ncomms13938)
• All-Oxide MoOx/SnOx Charge Recombination Interconnects for Inverted Organic Tandem Solar Cells, Adv. Energy Mater. 8, 1702533 (2018)
  T. Becker, S. Trost, A. Behrendt, I. Shutsko, A. Polywka, P. Görrn, P. Reckers, C. Das, T. Mayer, D. Di Carlo Rasi, K. H. Hendriks, M. M. Wienk, R. A. J. Janssen, and T. Riedl
  (See online at https://doi.org/10.1002/aenm.201702533)
• Metal Oxide-Based Charge Extraction and Recombination Layers for Organic Solar Cells In: The Future of Semiconductor Oxides in Next-Generation Solar Cells, Elsevier, p. 159-181 (2018)
  T. Riedl
  (See online at https://doi.org/10.1016/b978-0-12-811165-9.00005-3)
• Extremely robust gas quenching deposition of halide perovskites on top of hydrophobic hole transport materials for inverted (p-i-n) solar cells by targeting the precursor wetting issue, ACS Applied Mater. & Interfaces 11, 40172 (2019)
  K. O. Brinkmann, J. He, F. Schubert, J. Malerczyk, C. Kreusel, F. van gen Hassend, S. Weber, J. Song, J. Qu, and T. Riedl
  (See online at https://doi.org/10.1021/acsami.9b15867.s001)
• Impermeable charge transport layers enable aqueous processing on top of perovskite solar cells, Adv. Energy Mater. 10, 1903897 (2020)
  T. Gahlmann, K. O. Brinkmann, T. Becker, C. Tückmantel, C. Kreusel, F. van gen Hassend, S. Weber, and T. Riedl
  (See online at https://doi.org/10.1002/aenm.201903897)
• The Electronic Structure of MAPI-Based Perovskite Solar Cells: Detailed Band Diagram Determination by Photoemission Spectroscopy Comparing Classical and Inverted Device Stacks, Advanced Energy Materials, 10, 2002129 (2020)
  T. Hellmann, C. Das, T. Abzieher, J.A. Schwenzer, M. Wussler, R. Dachauer, U.W. Paetzold, W. Jaegermann, and T. Mayer
  (See online at https://doi.org/10.1002/aenm.202002129)
• Perovskite - organic tandem solar cells with indium oxide interconnect, Nature
  K. O. Brinkmann, T. Becker, F. Zimmermann, T. Gahlmann, M. Theisen, T. Haeger, S. Olthof, C. Kreusel, M. Günster, T. Maschwitz, F. Göbelsmann, C. Koch, D. Hertel, P. Caprioglio, L. Perdigon, A. Al-Ashouri, L. Merten, A. Hinderhofer, L. Gomell, S. Zhang, F. Schreiber, S. Albrecht, K. Meerholz, D. Neher, M. Stolterfoht, and T. Riedl
  (See online at https://doi.org/10.1038/s41586-022-04455-0)