A Simple n-Dopant Derived from Diquat Boosts the Efficiency of Organic Solar Cells to 18.3%

Abstract
Molecular doping has recently been shown to improve the operating characteristics of organic photovoltaics (OPVs). Here, we prepare neutral Diquat (DQ) and use it as n-dopant to improve the performance of state-of-the-art OPVs. Adding DQ in ternary bulk-heterojunction (BHJ) cells based of PM6:Y6:PC71BM is found to consistently increase their power conversion efficiency (PCE) from 16.7 to 17.4%. Analyses of materials and devices reveal that DQ acts as n-type dopant and morphology modifier for the BHJ leading to observable changes in its surface topography. The resulting n-doped BHJs exhibit higher optical absorption coefficients, balanced ambipolar transport, longer carrier lifetimes and suppressed bimolecular recombination, which are ultimately responsible for the increased PCE. The use of DQ was successfully extended to OPVs based on PM6:BTP-eC9:PC71BM for which a maximum PCE of 18.3% (uncertified) was achieved. Our study highlights DQ as a promising dopant for application in next generation organic solar cells.

Citation
Lin, Y., Nugraha, M. I., Firdaus, Y., Scaccabarozzi, A. D., Aniés, F., Emwas, A.-H., … Anthopoulos, T. D. (2020). A Simple n-Dopant Derived from Diquat Boosts the Efficiency of Organic Solar Cells to 18.3%. ACS Energy Letters, 3663–3671. doi:10.1021/acsenergylett.0c01949

Acknowledgements
This publication is based upon work supported by the King Abdullah University of Science and Technology (KAUST) Office of Sponsored Research (OSR) under Award No. OSR2018-CARF/CCF-3079, No. OSR-2019-CRG8-4095.3, and No. OSR-2020-CRG8-4095.2. GIWAXS experiments were performed at the BL11 NCD-SWEET beamline at the ALBA Synchrotron (Spain) with the collaboration of ALBA staff. L.T. acknowledges support for the computational time granted from GRNET in the National HPC facility -ARIS - under project FRAME.

Publisher
American Chemical Society (ACS)

Journal
ACS Energy Letters

DOI
10.1021/acsenergylett.0c01949

Additional Links
https://pubs.acs.org/doi/10.1021/acsenergylett.0c01949

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