Efficiency Potential of Singlet Fission Enhanced Silicon Solar Cells using Different Energy Transfer Schemes
Benjamin Daiber a, Koen v.d. Hoven a, Moritz H. Futscher a, Bruno Ehrler a
a Center for Nanophotonics, AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV19)
Roma, Italy, 2019 May 12th - 15th
Organizers: Prashant Kamat, Filippo De Angelis and Aldo Di Carlo
Oral, Benjamin Daiber, presentation 179
DOI: https://doi.org/10.29363/nanoge.hopv.2019.179
Publication date: 11th February 2019

Silicon is the dominating solar cell material, therefore add-ons on the silicon solar cell that can improve the power conversion efficiency are urgently needed. In certain organic materials singlet fission generates two triplet (spin 1) excitons from one singlet (spin 0) exciton. If the triplet excitons are harvested in the silicon solar cell the efficiency could be dramatically increased, as we show. There are different transfer pathways between the organic singlet fission material and silicon. We have simulated the achievable efficiency for each transfer path with realistic assumptions such as a singlet fission quantum efficiency of 1.7 (1.7 e-h pairs per high energy photon), a transmission loss of 5%, and a 50 meV Stokes shift in case of optical transmission.

Even with these realistic assumptions, the efficiency of a silicon/singlet fission solar cell can be as high as 34% when combined with the current record silicon solar cell of 27%. We found that dissociating the triplet excitons at the interface leads to a large potential efficiency gain because a triplet energy lower than the silicon bandgap still leads to charge generation, and allows for high current generation. We also find that current singlet fission materials do not absorb light strongly enough, motivating sensitization schemes. Finally, we compare the singlet fission/silicon solar cells to the efficiency potential of perovskite/silicon tandem solar cells. We find that tandem cells are particularly beneficial for a silicon base cell with low efficiency, while a highly efficient silicon solar cells benefits less from the perovskite top cell. In contrast, the efficiency gain from the singlet fission layer is almost constant for all silicon base cells, and for highly efficient silicon cells would clearly outperform a high-efficiency perovskite top cell.

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