Defence of doctoral thesis in the field of applied physics, M.Sc. Aapo Poskela

Dye solar cells are an emerging third generation photovoltaic technology with advantages such as low production costs and adjustable aesthetics through multiple dye colors. They also excel in low-light conditions, which makes them an excellent choice for indoor and building-integrated applications. The largest obstacle for large-scale commercial success of dye solar cells is their lifetime. While dye solar cells have been recorded to reach over 10,000 hours of stable operation, simultaneously achieving high efficiency, long lifetime and low production costs is proving to be a challenge.

The overall purpose of the thesis is to give a comprehensive overview of dye solar cell stability research by discussing how different aging conditions and materials impact the lifetime of dye solar cell devices, and by providing insight into aging methodology itself. Currently, dye solar cell stability research appears to lack standardized methods and rules and the goal of the thesis is to help inform forming of such standards.

Most stability studies age the dye solar cell samples in open circuit. While unrealistic, the findings of this thesis demonstrate that the degradation behavior in open circuit is similar to the degradation in cells connected to a load. Thus, open circuit aging is good approximation when lacking more sophisticated aging equipment. Another important aspect that was considered was the role of UV light in dye solar cell degradation. Many studies age dye solar cells with a light spectrum without a UV component, while assuming that a UV filter will protect the samples adequately in outdoor use. This thesis demonstrates that even a state-of-the-art UV filter does not remove enough UV to prevent significant increase in degradation rate, which means that UV should be considered in all stability research. The thesis also includes three separate case stability studies: the first outdoor stability study of dye solar cells in harsh outdoor conditions, the effect of electrolyte soaked nanocellulose films to the performance and stability of dye solar cells and comparison between stability of platinum and PEDOT catalyst layers.

The findings of this thesis suggest that stability research practices in the field of dye solar cells should be reviewed and standardized, enabling comparison between results of different research groups.

Opponent is Professor Aldo di Carlo, University of Rome "Tor Vergata", Italy

Custos is Professor Peter Lund, Aalto University School of Science, Department of Applied Physics

Contact details of the doctoral student: [email protected]

The public defence will be organised via Zoom. Link to the event

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The dissertation is publicly displayed 10 days before the defence in the publication archive Aaltodoc of Aalto University

Electronic thesis