• Sêr SAM

Sêr SAM Group Member Awarded HOPV 2021 Oral Contribution Prize

Updated: Jun 4

Congratulations to one of our PhD students, Stefan Zeiske, on his prize awarded at the 13th International Conference on Hybrid and Organic Photovoltaics (HOPV) which was held online from 24 to 28 May. Stefan was awarded the “Best Oral Contribution from MDPi Materials Journal” for his presentation titled “Direct Observation of Trap-Assisted Recombination in Organic Photovoltaic Devices”. The contributing authors to this work are Sêr SAM members Dr Oskar. J Sandberg, Dr Nasim Zarrabi, Dr Wei Li, Sêr-Cymru Chair Professor Paul Meredith and Rising Star Fellow Dr Ardalan Armin. This work has also been accepted into Nature Communications and is currently awaiting publication.

Stefan’s talk generated valuable discussion and will continue to encourage idea sharing and lead to further collaboration as he continues his work. We are very pleased to share Stefan’s excitement for being awarded this prize and once again, offer our greatest congratulations!

For further information, please see the following abstract for Stefan’s HOPV contribution:

“One of the most important photocurrent loss mechanisms limiting the power-conversion efficiency in all solar cells is trap-assisted recombination caused by localized sub-gap states. The presence and relevance of this first-order recombination in organic photovoltaic devices is still a subject of current debate, hindering the field as it seeks to push the boundaries of efficiency towards inorganic and perovskite semiconductor counterparts. In this work we conduct wide dynamic range, sensitive intensity-dependent photocurrent measurements combined with one-dimensional drift-diffusion simulations. Our key finding is that first-order, trap-assisted recombination appears to be universally present in a large variety of fullerene and non-fullerene acceptor systems - including state-of-the-art PM6:BTP-eC9 achieving above 15 % power conversion efficiency.1 The trap states are found to be situated eV below the transport level edges of acceptor: donor blends with trap densities lying between cm-3. We show that the trap-assisted recombination via these deep sub-gap states induces not only losses in the photocurrent but also limits the open-circuit voltage leading to ideality factors between 1 and 2. Hence, our findings deliver new insight into the role and nature of trap states in organic light-harvesting devices, and shed new light on the complexity and variability of ideality factors in solar cells.”

1. Zeiske, S. et al. Direct Observation of Trap-Assisted Recombination in Organic Photovoltaic Devices. submitted (2020).

You can also listen to Stefan's talk HERE (Copyright Stefan Zeiske 2021):

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