Enhanced Stability of Tin Halide Perovskite Photovoltaics Using a Bathocuproine - Copper Top Electrode
Anjana Wijesekara a, Marc Walker b, Yisong Han b, David Walker b, Steven Huband b, Ross Hatton a
a Department of Chemistry, University of Warwick, Coventry, CV4 7AL, United Kiongdom
b Department of Physics, University of Warwick, Coventry CV4 7AL.
International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV22)
València, Spain, 2022 May 19th - 25th
Organizers: Pablo Docampo, Eva Unger and Elizabeth Gibson
Oral, Anjana Wijesekara, presentation 105
DOI: https://doi.org/10.29363/nanoge.hopv.2022.105
Publication date: 20th April 2022

Organo-tin halide perovskite photovoltaics (PPVs) have the advantage over their lead analogues that they don’t contain the toxic element lead which is well known to bioaccumulate. The Achilles’ heel of tin perovskites for PV applications is their higher susceptibility to oxidation in air which stems from the tendency of Sn2+ to convert to the more thermodynamically stable +4 oxidation state upon exposure to ambient air. This talk will present results relating to an unencapsulated organo-tin halide PPV device exhibiting record stability for an organo-tin PPV device when tested under continuous one sun solar illumination in ambient air under electrical load, made possible by the use of a bathocuproine | copper cathode in an inverted device architecture, and explain the underlying reasons for the exceptional stability compared to conventional silver cathode.[1] Experimental evident will be presented that shows that compact copper electrodes are far more resistant to corrosion by iodine gas (evolved when organo-tin halide decomposes) and towards adverse morphological evolution and ingress of oxygen and water molecules through the electrode, than conventional silver electrodes. In addition, the findings of preliminary studies into further improvements in device stability achieved using bilayer metal cathodes (with copper interfacing the bathocuproine layer) will also be presented. In summary, the results presented will show that copper should be the metal of choice for the reflective cathode in inverted tin perovskite PVs when the material interfacing the metal interacts strongly with it, enabling compact film formation and a stable interface towards copper diffusion into the adjacent charge transport layer.

The authors would like to thank the University of Warwick for the award of a Chancellor’s International Scholarship to Anjana Wijesekara.

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