Performance Enhancement of Organic Solar Cells by Bulk Heterojunction Modification


Organic photovoltaics have advanced rapidly in recent years due to their low cost, lightweight, semi-transparency, and promising indoor applications. To date, the record power conversion efficiency values for bulk-heterojunction organic photovoltaics exceed 19%. However, despite remarkable progress, the above performance level is still lower than the actual power conversion efficiency limit. Therefore, the development of new material synchronous optimization device engineering has become an urgent matter to promote power conversion efficiency to a new level.

We first add two new N-type dopants Ethyl Viologen and Methyl Viologen into PM6:BTP-eC9:PC71BM BHJ, which leads to 19.033%, 18.611% power conversion efficiency and impressive 80%, 79.2% fill factor, respectively. It is found Ethyl Viologen and Methyl Viologen could be not only the N-type dopants but also the surface modifier, which could enhances the absorption coefficient, balanced charge carrier mobilities, longer carrier time and suppress the charge recombination.

Next, two dimeric acceptor materials of DIBP3F-Se and DIBP3F-S were designed and synthesized. The influence of controlled conformation on molecular packing, morphology and performance was investigated. The S-shaped DIBP3F-Se exhibited more coplanar conformation, enhanced light absorption, tighter π-π stacking and a more ordered molecular packing, better miscibility with PM6 in comparison with U-shaped DIBP3F-S as its structural analogue. Thus, PSC based on PM6:DIBP3F-Se delivered a higher PCE of 18.09% than that based on DIBP3F-S and among the highest values reported for OAs-based PSCs.

Lastly, we synthesized an asymmetric non-fullerene small molecular acceptor (SMA), named BTP-J17, and investigated its application in polymer organic photovoltaics (PM6:DIBP3F-Se). BTP-J17, which demonstrates improved miscibility with DIBP3F-Se, significantly enhances the open-circuit voltage by facilitating better molecular packing. Notably, BTP-J17 is situated at the host donor-acceptor interface, acting as an effective charge transport channel, leading to enhanced exciton dissociation and charge extraction, improved charge mobilities, reduced charge recombination and energy loss. Consequently, the introduction of BTP-J17 not only ensures an exceptional open-circuit voltage of 0.941 V but also achieves higher values of short-circuit current and fill factor. These improvements collectively boost the power conversion efficiency from 18.40% to 19.60%. Moreover, the device displays an extended outdoor stability with a T80 of 7 weeks.


MSE Ph.D. Candidate Zhaoheng Ling, supervised by Prof. Thomas D. Anthopoulos

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24 Sep, 2024
01:30 PM - 04:00 PM
Al-Kindi Building (Bldg. 5), Room 5209