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High-efficiency organic solar cells with low non-radiative recombination loss and low energetic disorder

Nature Photonics volume 14, pages 300–305 (2020)Cite this article

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Abstract

Energy loss within organic solar cells (OSCs) is undesirable as it reduces cell efficiency1,2,3,4. In particular, non-radiative recombination loss3 and energetic disorder5, which are closely related to the tail states below the band edge and the overall photon energy loss, need to be minimized to improve cell performance. Here, we report how the use of a small-molecule acceptor with torsion-free molecular conformation can achieve a very low degree of energetic disorder and mitigate energy loss in OSCs. The resulting single-junction OSC has an energy loss due to non-radiative recombination of just 0.17 eV and a high power conversion efficiency of up to 16.54% (certified as 15.89% by the National Renewable Energy Laboratory). The findings take studies of organic photovoltaics deeper into a new regime, beyond the limits of energetic disorder and large energy offset for charge generation.

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Fig. 1: Photon energy loss analysis in solar cells.
Fig. 2: Chemical structure of the polymer donor and small-molecular acceptor used in this study and optical properties of the absorbers.
Fig. 3: Photovoltaic characterization.
Fig. 4: Sensitive EQE measurements, analysis of energetic disorder and dependence of EL spectra on injection current densities.

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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. Raw data essential to the work are available online as Source Data files.

Code availability

Computer code used to generate results (to calculate the spontaneous emission rate, simulate maximum open-circuit voltage, generate fits to the spectral features in EL spectra) for this study is available from the corresponding author (H.W.) upon request.

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Acknowledgements

H.W. thanks the National Natural Science Foundation of China for financial support (no. 51521002). Y.Z. acknowledges the National Natural Science Foundation of China (no. 21875286), the National Key Research & Development Projects of China (no. 2017YFA0206600) and the Science Fund for Distinguished Young Scholars of Hunan Province (2017JJ1029). Z.H. acknowledges the National Natural Science Foundation of China for financial support (nos. 51622302 and 21733005). We thank T. Song and H. Meng for solar cell performance verification, J. Zhang for acquiring GIWAXS analysis and B. Xiao for temperature-dependent current–voltage characteristics measurements. We thank S. Bilson for proof reading.

Author information

Author notes

  1. These authors contributed equally: Sha Liu, Jun Yuan, Wanyuan Deng.

Authors and Affiliations

  1. Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou, P. R. China

    Sha Liu, Wanyuan Deng, Yuan Xie, Quanbin Liang, Zhicai He, Hongbin Wu & Yong Cao

  2. College of Chemistry and Chemical Engineering, Central South University, Changsha, P. R. China

    Jun Yuan, Mei Luo & Yingping Zou

  3. State Key Laboratory of Powder Metallurgy, Central South University, Changsha, P. R. China

    Yingping Zou

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Contributions

Y.Z. and H.W. conceived the idea. S.L. fabricated and characterized the devices. Y.Z., J.Y. and M.L. designed the molecule structure of the electron acceptor, and J.Y. and M.L. synthesized the compound. W.D. and S.L. performed sensitive EQE, EL, photoluminescence and temperature-dependent photovoltage/photocurrent characteristics measurements. W.D. carried out analysis of the EL spectra and temperature-dependent photovoltage characteristics, and carried out the transient absorption measurements. Y.X. determined the optical gap, the energy of the charge transfer states of the absorbers and carried out IQE measurements. J.Y. performed morphological characterization. Q.L. performed transient photovoltage and transient photocurrent measurements. S.L. and Z.H. prepared and brought samples to NIM for certification. S.L. coordinated solar cells performance verification at NREL and prepared the samples. H.W., Y.Z. and Y.C. coordinated the project. H.W. and Y.Z. wrote the manuscript, while all authors contributed to data analysis, interpretation and discussion of the results.

Corresponding authors

Correspondence to Yingping Zou or Hongbin Wu.

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Extended data

Extended Data Fig. 1 The context page of test report by the National Renewable Energy Laboratory (NREL).

a, The test summary for a champion cell (#892-b) tested under the initial asymptotic scan. The asymptotic scan was measured through holding the device at the bias near the maximal power condition. b, The test summary for the cell tested in the second round asymptotic scan. c, The test summary for the cell tested under the standard sweep condition.

Source data

Extended Data Fig. 2 Photon energy loss analysis on the devices investigated in this study.

Device parameters of representative devices from various photovoltaic material systems in literature are also included for comparison.

Supplementary information

Supplementary Information

Supplementary Figs. 1–18, Tables 1 and 2, and references.

Reporting Summary

Source data

Source Data Fig. 2

Absorbance spectra Source Data.

Source Data Fig. 3

Current density–voltage (J–V) characteristics and EQE spectra Source Data of the best-performing OSCs.

Source Data Fig. 4

The measured EL spectrum, the experimental EQE spectrum and the deduced EQE spectrum determined from the EL spectrum Source Data.

Source Data Extended Data Fig. 1

Test report by NREL Source Data.

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Liu, S., Yuan, J., Deng, W. et al. High-efficiency organic solar cells with low non-radiative recombination loss and low energetic disorder. Nat. Photonics 14, 300–305 (2020). https://doi.org/10.1038/s41566-019-0573-5

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