Yahui Tang1,2,Alexandra Stuart1,Timothy van der Laan2,Girish Lakhwani1
The University of Sydney1,Commonwealth Scientific and Industrial Research Organisation2
Yahui Tang1,2,Alexandra Stuart1,Timothy van der Laan2,Girish Lakhwani1
The University of Sydney1,Commonwealth Scientific and Industrial Research Organisation2
Strong light-matter coupling in organic solar cells (OSCs) has recently shown great potential in increasing the power conversion efficiencies of light.<sup> 1–4</sup> Strong light-matter coupling creates new hybrid states termed exciton-polaritons, and the formation of polaritons in OSCs can significantly influence device performance. It has been shown in thermally evaporated planar heterojunction OSCs that exciton-polaritons can reliably exist at room temperature and leads to more efficient energy transfer.<sup>1</sup> Yet, it has not been demonstrated for solution-processed bulk-heterojunction OSC devices, whereas the latter is more scalable for practical applications. Here, we report that exciton-polaritons can reliably exist in solution-processed bulk-heterojunction OSCs and their influence on device properties. Combining time-resolved spectroscopic measurements for thin films and transient photocurrent/photovoltage decay measurements for devices, we investigated the photo- and device physics of cavity OSCs. We find that the benefits of strong coupling to OSCs are two-fold. Firstly, the charge photogeneration through the new pathway facilitated by the exciton-polaritons is enhanced compared to the reference OSC devices. Secondly, we find that the energy of the charge transfer state is blue-shifted, accompanied by the longer charge carrier lifetime observed in the transient photovoltage decay measurements. Our work demonstrates that strong coupling is a promising avenue for further improving the device properties of OSCs.<br/><br/>References<br/>1. M. Wang, M. Hertzog, K. Börjesson, Nat Commun. 12, 1874 (2021).<br/>2. V. C. Nikolis, A. Mischok, B. Siegmund, J. Kublitski, X. Jia, J. Benduhn, U. Hörmann, D. Neher, M. C. Gather, D. Spoltore, K. Vandewal, Nat Commun. 10, 3706 (2019).<br/>3. C. A. Delpo, S. U. Z. Khan, K. H. Park, B. Kudisch, B. P. Rand, G. D. Scholes, Journal of Physical Chemistry Letters. 12, 9774–9782 (2021).<br/>4. B. Liu, X. Huang, S. Hou, D. Fan, S. R. Forrest, Optica. 9, 1029–1036 (2022).