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Dilution effect for highly efficient multiple-component organic solar cells

Abstract

Although the multiple-component (MC) blend strategy has been frequently used as a very effective way to improve the performance of organic solar cells (OSCs), there is a strong need to understand the fundamental working mechanism and material selection rule for achieving optimal MC-OSCs. Here we present the ‘dilution effect’ as the mechanism for MC-OSCs, where two highly miscible components are molecularly intermixed. Contrary to the aggregation-induced non-radiative decay, the dilution effect enables higher luminescence quantum efficiencies and open-circuit voltages (VOC) in MC-OSCs via suppressed electron–vibration coupling. The continuously broadened bandgap together with reduced electron–vibration coupling also explains the composition-dependent VOC in ternary blends well. Moreover, we show that electrons can transfer between different acceptors, depending on the energy offset between them, which contributes to the largely unperturbed charge transport and high fill factors in MC-OSCs. The discovery of the dilution effect enables the demonstration of a high power conversion efficiency of 18.31% in an MC-OSC.

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Fig. 1: Schematic of dilution effect and optoelectronic properties light-emitting species (4TIC) and diluent molecule (ITIC).
Fig. 2: Inheriting dilution effect from 4TIC–ITIC film to MC-OSCs with different ITIC loading.
Fig. 3: Carrier dynamics among PBDB-T, ITIC and 4TIC.
Fig. 4: Charge transport behaviour in blend films.
Fig. 5: Extended systems for dilution strategy.

Data availability

The data that support the findings of this study are available from the corresponding authors on reasonable request.

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Acknowledgements

This work was supported by the Office of Naval Research (grant nos. N00014-17-1-2201, N00014-20-1-2191), the Air Force Office of Scientific Research (grant no. FA9550-18-1-0046), the National Natural Science Foundation of China (grant no. 21734008) and National Key Research and Development programme of China (grant no. 2019YFA0705900). A.K.Y.J. thanks the support from the Boeing-Johnson Chair Professorship and Lee Shau Kee Chair Professorship in Materials Science. L.Z. thanks the support from the research startup fund of Zhejiang University.

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Contributions

L.Z. conceived the idea, designed and carried out experiments on film/device fabrication and characterization, and analysed the data. S.B.J. designed, carried out and analysed spectroscopic studies, and modelled the percolation-limited charge transport. Y. Li fabricated and measured the champion devices. X.S. and F.L. synthesized the materials. Y.M. and R.J.S. carried out experiments on the electroluminescence and PL spectra. Y. Liu, D.S.G. and H.W.H. advised on theoretical analyses of luminescence behaviours. L.Z. and S.B.J. wrote the paper. A.K.Y.J. and H.C. supervised the research. All authors contributed to discussion, writing and revision.

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Correspondence to Hongzheng Chen or Alex K.-Y. Jen.

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Supplementary Information

Experimental section, Supplementary Figs. 1–50, Appendices 1–5 and Tables 1–7.

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Zuo, L., Jo, S.B., Li, Y. et al. Dilution effect for highly efficient multiple-component organic solar cells. Nat. Nanotechnol. 17, 53–60 (2022). https://doi.org/10.1038/s41565-021-01011-1

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