Ronald Österbacka
（
Professor of Åbo Akademi University）
Abstract of Speech: Understanding and minimizing non-radiative recombination pathways is key to enhanced efficiencies in emerging solar cells, such as perovskite solar cells (PSC) and organic photovoltaics (OPV). Non-radiative recombination in any form, i.e. trap-assisted, or surface recombination of minority carriers at the (wrong) electrode will inevitably lead to lower efficiencies1. However, given the fast development of the efficiencies, the stability of OPVs is still not satisfactory.
In this talk, I will focus on the charge transport layers (CTL) and their properties in increasing efficiency and stability. I will focus on the passivation of metal-oxides in nip-solar cells for OPVs. The criterion that the CTL is conducting2 will simultaneously lead to loss of selectivity.3 We have identified and mitigated an important loss-factor caused by ZnO in OPVs. Surface defects in ZnO cause n-doping in a thin layer close to the cathode, causing a loss of Jsc. By inserting a thin layer of SiOxNy from solution processing, the recombination zone will be removed, with increased efficiency and lifetime as a result.4
(1) Sandberg, O. J.; Nyman, M.; Österbacka, R. Effect of Contacts in Organic Bulk Heterojunction Solar Cells. Phys. Rev. Appl. 2014, 1 (2), 024003. https://doi.org/10.1103/PhysRevApplied.1.024003.
(2) Le Corre, V. M.; Stolterfoht, M.; Perdigón Toro, L.; Feuerstein, M.; Wolff, C.; Gil-Escrig, L.; Bolink, H. J.; Neher, D.; Koster, L. J. A. Charge Transport Layers Limiting the Efficiency of Perovskite Solar Cells: How To Optimize Conductivity, Doping, and Thickness. ACS Appl. Energy Mater. 2019, 2 (9), 6280–6287. https://doi.org/10.1021/acsaem.9b00856.
(3) Nyman, M.; Ahläng, C.; Dahlström, S.; Pranav, M.; Benduhn, J.; Qudsia, S.; Smått, J.-H.; Spoltore, D.; Österbacka, R. Highly Conductive Charge Transport Layers Impair Charge Extraction Selectivity in Thin‐Film Solar Cells. Adv. Energy Sustain. Res. 2023, 4 (10), 2300030. https://doi.org/10.1002/aesr.202300030.
(4) Liu, B.; Sandberg, O. J.; Qin, J.; Liu, Y.; Wilken, S.; Wu, N.; Yu, X.; Fang, J.; Li, Z.; Huang, R.; Zha, W.; Luo, Q.; Tan, H.; Österbacka, R.; Ma, C.-Q. Inverted Organic Solar Cells with an in Situ-Derived SiOxNy Passivation Layer and Power Conversion Efficiency Exceeding 18%. Nat. Photonics 2025. https://doi.org/10.1038/s41566-024-01574-0.
Biography of the Speaker:Ronald Österbacka obtained his Ph.D. in physics with distinction from Åbo Akademi University in 1999. During his Ph.D., he spent one year with Prof. Z. Valy Vardeny at the University of Utah. He did his PostDoc as an Academy of Finland research fellow and became a full professor in physics at ÅAU in 2005. Österbacka holds a Suzhou Foreign Academician Laboratory fellowship at the Printed Electronics Research Center, Suzhou Institute for Nano-tech and Nano-bionics. Österbacka is the recipient of the 2023 professor Theodore Homén’s prize awarded by the Finnish Society for Science and Letters. Österbackas specialty area is electro-optical properties of disordered, organic materials. In particular, the charge transport and recombination in thin-film solar cells and the demonstration of novel solution-processable organic electronic devices. The Organic Electronics group at Åbo Akademi University, headed by Österbacka, has made fundamental discoveries in developing ion-modulated organic transistors as sensors and for paper electronics. Organic bioelectronic devices have recently been developed to measure and control cell functions.
