Projects
SolStore II
In my current project, I develop multi-junction solar cells to bridge the gap when higher voltage output is required. The aim is to increase the energy density of photo-electrochemical devices. Multiple junctions have been proven to provide an alternative to modules when overall size is limited. This can be the case in low power applications.
First supervisor
Dr. Uli Würfel
PhD Project
SolStore
My work focused on the development of photo-electrochemical devices that integrate organic solar cells and storage media to power small power applications in the framework of the Internet-of-Things. Three integration modes were identified, progressing in complexity from mode I to mode II and mode III. Mode I involves wired connections between individual harvesting and storage devices. In Mode II we achieve the monolithic integration of constituent parts. And finally, Mode III requires multifunctional materials which are capable of simultaneously capturing and storing energy.
Project outcomes
In general, we realized mode II and mode III devices, proving this approach to be useful for powering small gadgets. In mode II, we used well-established and high-performing organic solar cell materials for the harvesting part, which we combined monolithically with supercapacitors and Li-ion batteries for storage. This shows that this is a very versatile solution for powering small autonomous devices. We proposed a new figure of merit to assess overall device performance, considering cycle energy utilization for a photo-charge-discharge process. We identified the importance of illumination time, discharge currents and careful control of these variables and solar cell parameters as key factors in achieving high photo-electrochemical performance.
For mode III, we explored phenothiazine-based conjugated donor-acceptor copolymers as a suitable multifunctional material. The research showed that creating multifunctional materials is possible, but it also highlighted the challenges involved. Balancing the properties to meet the requirements of both charge storage and solar cell performance can be conflicting. Therefore, the optimal multifunctional materials may demonstrate only moderate performance in both types of devices.
Dissertation link: https://onlinelibrary.wiley.com/doi/10.1002/ente.202301421
First supervisor
Dr. Uli Würfel