SCIENCE CHINA Materials, Volume 64 , Issue 11 : 2629-2644(2021) https://doi.org/10.1007/s40843-021-1703-4

Remove the water-induced traps toward improved performance in organic solar cells

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  • ReceivedApr 25, 2021
  • AcceptedMay 7, 2021
  • PublishedJul 16, 2021


Funded by

the National Natural Science Foundation of China(NSFC)

the Fundamental Research Funds for the Central Universities

and the opening project of Key Laboratory of Materials Processing and Mold and Beijing National Laboratory for Molecular Sciences(BNLMS201905)


This work was supported by the National Natural Science Foundation of China (NSFC) (51773157 and 52061135206), and the Fundamental Research Funds for the Central Universities. The authors also thank the support of the opening project of Key Laboratory of Materials Processing and Mold and Beijing National Laboratory for Molecular Sciences (BNLMS201905). We thank Yihua Chen and Huanping Zhou for conducting the thermal admittance spectroscopy (TAS) measurements.

Interest statement

The authors declare that they have no conflict of interest.

Contributions statement

Shi M and Min J conceived the ideas and coordinated the work. Shi M designed the experiments, performed the fabrication of solar cell devices and data analysis. Wang T contributed to the donor polymer materials. Wu Y contributed to the acceptor materials. Xie G conducted the OLED performance measurement. Pei D and Ye L conducted the fabrication of OFET devices and their performance measurement. Wang H and Wang T did the capacitance spectroscopy measurements. Sun R and Wu Q did the atomic force microscopy measurements. Yang W and Wang W did the transient physics measurements. Shi M and Min J contributed to manuscript preparation, and Shi M supervised by Min J conceived and directed the project. All authors commented on the manuscript.

Author information

Mumin Shi received a BSc degree from Northwest Agriculture & Forestry University in 2018. Now she is pursuing her MSc degree at the Institute for Advanced Studies, Wuhan University and her research focuses on the material and device stability in organic solar cells.

Jie Min is a full professor at the Institute for Advanced Studies, Wuhan University. During 2008–2011, he focused on the photovoltaic materials in the group of prof. Yongfang Li as a joint master. In 2015, he completed his PhD study in the Institute of Materials for Electronics and Energy Technology (i-MEET) at the Friedrich Alexander University Erlangen-Nuernberg under the supervision of prof. Christoph J. Brabec. From October 2015, he was a postdoctoral fellow in the group of Prof. Brabec in i-MEET. He joined Wuhan University in 2017. His major research interest is in the physics and chemistry of organic photovoltaic materials, and photovoltaic device physics and engineering.


Supplementary information

Supporting data are available in the online version of the paper.


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  • Figure 1

    Effect of water removal through various strategies on device performance. (a) Molecular structures of PM6 and Y6. (b) Left: the presence of water-induced traps (red) in the microstructures of polymer (light orange) and small molecule acceptor (lavender) materials. Middle: methods of water removal in BHJ OSCs, including using AR-CF, anhydrous HPLC-CF and SWE method. Right: (i) AR-CF-processed PM6:Y6 blend initially containing residual water after spin-coating. (ii) HPLC-CF-processed PM6:Y6 blend initially containing residual water after spin-coating. The residual water molecules result from the photovoltaic materials that absorbed the water during the preparation and transportation in air. (iii) HPLC-CF-processed PM6:Y6 blend prepared with the SWE method. A short anneal for 20 min is used, which removes the solvent and water molecules in the bottle. (c) J-V characteristics of the relevant devices based on the various blends coated according to the above-mentioned solution preparation conditions. (d) Histograms of the PCE counts for 26 individual AR-CF devices, 26 individual HPLC-CF devices, and 26 individual SWE devices.

  • Figure 2

    Charge transport, extraction and recombination in blends. The corresponding current-voltage (I-V) curves from (a) hole-only devices (symbols) or (b) electron-only devices (symbols) and model fits (dashed lines) for the PM6:Y6 blends with different processing conditions. Slope versus relevant voltage curves for the PM6:Y6 blends with different processing conditions. (c) The photo-CELIV traces for the devices after a delay time of 0.5 µs. (d) Charge carrier lifetime τ, obtained from TPV measurements, as a function of charge density n, calculated from CE curves under Voc conditions (from 0.15 to 2.50 suns). The dashed lines represent linear fits of the data. (e) Photocurrent versus Veff in the relevant devices based on different processing conditions. (f) Normalized TPC data for the relevant devices. The illumination pulse intensity was 150 mW cm−2 (light pulse of 50 µs). Inset: the figure of the comparison of charge carrier lifetime τ (obtained from TPV tests) and charge extraction time τ (obtained from TPC tests). The bulk-heterojunction systems of AR-CF, HPLC-CF and SWE of (g) charge carrier density n, determined via capacitance spectroscopy, (h) recombination current density Jrec and fitting curves, and (i) competitive factors θ, determined via effect extraction time τex and charge carrier lifetime τrec.

  • Figure 3

    Chemical structures, device performance and transport properties. (a) Molecular structures of the four photovoltaic systems, including J101:ITIC, J71:MeIC, PTB7-Th:PC70BM, and TBFT-TR:PC70BM. (b) J-V characteristics of the four types of devices with and without SWE approaches. (c) Top: average PCEs of the five photovoltaic systems without and with SWE treatments; bottom: the electron traps of hole-only devices and electron-only devices for the relevant blends without and with SWE treatments.

  • Figure 4

    Improving the performance of OLEDs and OFETs with SWE approaches. (a) Device structure of an SY-PPY OLED, (b) chemical structures of SY-PPY and PDPP2TBT. (c) Device structure of a PDPP2TBT OFET. (d) J-V-L characteristics of SY-PPV OLEDs without and with SWE treatments. (e) Luminous (cd A−1) and power (l m W−1) efficiencies as a function of the applied voltage of the SY-PPV OLEDs. (f) Representative transfer and (g) output characteristics, respectively. The transfer curve was collected with a voltage sweep rate of 50 mV s−1.

  • Table 1   Summary of photovoltaic parameters of the optimized PM6:Y6 solar cells, measured under the illumination of AM 1.5 G at 100 mW cm−2

    Processing conditions

    VOC (V)

    JSC (mA cm−2)

    JSC,EQEa (mA cm−2)

    FF (%)

    PCEmax (PCEavg) (%)






    15.25 (14.97b)






    15.83 (15.59b)






    17.10 (16.73b)

    SWE (AR-CF)





    15.79 (15.46d)







    JSC, EQE represents the integrated current density obtained from EQE spectra. b) The average PCE values with standard deviations were obtained from twenty devices. c) The anhydrous HPLC-CF purified in our lab was used to conduct the SWE method. d) The average PCE values with standard deviations were obtained from eight devices.

  • Table 2   Summary of the relevant physical parameters of the analysis of current-voltage characteristics, as well as the data of transient spectroscopic measurements



    Hole-only devices

    Electron-only devices


    Solar cells

    Mobility (×10−4

    cm2 V−1 s−1)


    (×1023 m−3)





    Mobility (×10−4

    cm2 V−1 s−1)


    (×1023 m−3)










    CF (AR)













    CF (HPLC)


























    Charge carrier lifetime τ1 achieved from the TPV spectra measured under one sun. b) CE time τ2 obtained from TPC tests.


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