High-efficiency small-molecule ternary solar cells with a hierarchical morphology enabled by synergizing fullerene and non-fullerene acceptors

Abstract

Using combinatory photoactive blends is a promising approach to achieve high power conversion efficiency in ternary organic photovoltaics. However, the fundamental challenge of how to manipulate the morphology of multiple components and correlate structure details via device performance has not been well addressed. Achieving an ideal morphology that simultaneously enhances charge generation and transport and reduces voltage loss is an imperative avenue to improve device efficiency. Here, we achieve a high power conversion efficiency of 13.20 ± 0.25% for ternary solar cells by using a combination of small molecules with both fullerene and non-fullerene acceptors, which form a hierarchical morphology consisting of a PCBM transporting highway and an intricate non-fullerene phase-separated pathway network. Carrier generation and transport find an optimized balance, and voltage loss is simultaneously reduced. Such a morphology fully utilizes the individual advantages of both fullerene and non-fullerene acceptors, demonstrating their indispensability in organic photovoltaics.

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Fig. 1: Properties and photovoltaic performance.
Fig. 2: Morphology investigations.
Fig. 3: Charge generation, extraction and recombination.
Fig. 4: Energy loss analysis.
Fig. 5: Illustration of the morphology and comparison of PCEmax and Eloss.

Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding authors upon reasonable request.

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Acknowledgements

We thank the National Basic Research Program of China (Program 973) (No. 2014CB643502), the National Key R&D Program of China (2017YFA0204700), the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB12010200) and the National Natural Science Foundation of China (21572234, 21661132006) for their financial support. Portions of this research were carried out at beamlines 7.3.3 and 11.0.1.2 at the Advanced Light Source and Molecular Foundry at the Lawrence Berkeley National Laboratory, which was supported by the Department of Energy (DOE), Office of Science and Office of Basic Energy Sciences. Y.J. and F.Z. acknowledge financial support from the Swedish Research Council (VR621-2013-5561), the Swedish Government Strategic Research Area in Material Science on Functional Materials at Linköping University (Faculty Grant SFO-Mat-LiU No 200900971) and the China Scholarship Council (CSC201606920028).

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Z.Z. and Q.Y. fabricated and optimized the devices; S.X. synthesized the NITI; J.S., Y.Q. and F.L. performed the morphology characterization and analysis; Y.J. performed the photoluminescence, electroluminescence and FTPS-EQE experiments, which were supervised by F.Z.; and X.Z. conceived and directed the project. All authors discussed the results and substantially contributed to the preparation of the manuscript.

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Correspondence to Feng Liu or Fengling Zhang or Xiaozhang Zhu.

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Zhou, Z., Xu, S., Song, J. et al. High-efficiency small-molecule ternary solar cells with a hierarchical morphology enabled by synergizing fullerene and non-fullerene acceptors. Nat Energy 3, 952–959 (2018). https://doi.org/10.1038/s41560-018-0234-9

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