logo

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

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

Abstract


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)


Acknowledgment

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.


Supplement

Supplementary information

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


References

[1] Li S, Li CZ, Shi M, et al. New phase for organic solar cell research: Emergence of Y-series electron acceptors and their perspectives. ACS Energy Lett, 2020, 5: 1554-1567 CrossRef Google Scholar

[2] Fukuda K, Yu K, Someya T. The future of flexible organic solar cells. Adv Energy Mater, 2020, 10: 2000765 CrossRef Google Scholar

[3] Lee C, Lee S, Kim GU, et al. Recent advances, design guidelines, and prospects of all-polymer solar cells. Chem Rev, 2019, 119: 8028-8086 CrossRef PubMed Google Scholar

[4] Guo J, Min J. A cost analysis of fully solution-processed ITO-free organic solar modules. Adv Energy Mater, 2019, 9: 1802521 CrossRef Google Scholar

[5] Wang T, Sun R, Shi M, et al. Solution-processed polymer solar cells with over 17% efficiency enabled by an iridium complexation approach. Adv Energy Mater, 2020, 10: 2000590 CrossRef Google Scholar

[6] Luo Z, Ma R, Liu T, et al. Fine-tuning energy levels via asymmetric end groups enables polymer solar cells with efficiencies over 17%. Joule, 2020, 4: 1236-1247 CrossRef Google Scholar

[7] Cui Y, Yao H, Zhang J, et al. Single-junction organic photovoltaic cells with approaching 18% efficiency. Adv Mater, 2020, 32: 1908205 CrossRef PubMed Google Scholar

[8] Yang W, Luo Z, Sun R, et al. Simultaneous enhanced efficiency and thermal stability in organic solar cells from a polymer acceptor additive. Nat Commun, 2020, 11: 1218 CrossRef PubMed ADS Google Scholar

[9] Yao H, Wang J, Xu Y, et al. Recent progress in chlorinated organic photovoltaic materials. Acc Chem Res, 2020, 53: 822-832 CrossRef PubMed Google Scholar

[10] Zhao J, Li Y, Yang G, et al. Efficient organic solar cells processed from hydrocarbon solvents. Nat Energy, 2016, 1: 15027 CrossRef ADS Google Scholar

[11] Sun R, Wang T, Luo Z, et al. Achieving eco-compatible organic solar cells with efficiency >16.5% based on an iridium complex-incorporated polymer donor. Sol RRL, 2020, 4: 2000156 CrossRef Google Scholar

[12] Liu Q, Jiang Y, Jin K, et al. 18% Efficiency organic solar cells. Sci Bull, 2020, 65: 272-275 CrossRef ADS Google Scholar

[13] Cheng P, Yang Y. Narrowing the band gap: The key to high-performance organic photovoltaics. Acc Chem Res, 2020, 53: 1218-1228 CrossRef PubMed Google Scholar

[14] Zheng Z, Yao H, Ye L, et al. PBDB-T and its derivatives: A family of polymer donors enables over 17% efficiency in organic photovoltaics. Mater Today, 2019, 35: 115-130 CrossRef Google Scholar

[15] Wang W, Chen B, Jiao X, et al. A new small molecule donor for efficient and stable all small molecule organic solar cells. Org Electron, 2019, 70: 78-85 CrossRef Google Scholar

[16] Wan X, Li C, Zhang M, et al. Acceptor-donor-acceptor type molecules for high performance organic photovoltaics—chemistry and mechanism. Chem Soc Rev, 2020, 49: 2828-2842 CrossRef PubMed Google Scholar

[17] Li X, Huang G, Chen W, et al. Size effect of two-dimensional conjugated space in photovoltaic polymers’ side chain: Balancing phase separation and charge transport. ACS Appl Mater Interfaces, 2020, 12: 16670-16678 CrossRef PubMed Google Scholar

[18] Heumueller T, Mateker WR, Sachs-Quintana IT, et al. Reducing burn-in voltage loss in polymer solar cells by increasing the polymer crystallinity. Energy Environ Sci, 2014, 7: 2974-2980 CrossRef Google Scholar

[19] Min J, Jiao X, Ata I, et al. Time-dependent morphology evolution of solution-processed small molecule solar cells during solvent vapor annealing. Adv Energy Mater, 2016, 6: 1502579 CrossRef Google Scholar

[20] Han YW, Jeon SJ, Lee HS, et al. Evaporation-free nonfullerene flexible organic solar cell modules manufactured by an all-solution process. Adv Energy Mater, 2019, 9: 1902065 CrossRef Google Scholar

[21] Zuo G, Linares M, Upreti T, et al. General rule for the energy of water-induced traps in organic semiconductors. Nat Mater, 2019, 18: 588-593 CrossRef PubMed ADS Google Scholar

[22] Kotadiya NB, Mondal A, Blom PWM, et al. A window to trap-free charge transport in organic semiconducting thin films. Nat Mater, 2019, 18: 1182-1186 CrossRef PubMed ADS Google Scholar

[23] Nicolai HT, Kuik M, Wetzelaer GAH, et al. Unification of trap-limited electron transport in semiconducting polymers. Nat Mater, 2012, 11: 882-887 CrossRef PubMed ADS Google Scholar

[24] Guo J, Wu Y, Sun R, et al. Suppressing photo-oxidation of non-fullerene acceptors and their blends in organic solar cells by exploring material design and employing friendly stabilizers. J Mater Chem A, 2019, 7: 25088-25101 CrossRef Google Scholar

[25] Adams J, Salvador M, Lucera L, et al. Water ingress in encapsulated inverted organic solar cells: Correlating infrared imaging and photovoltaic performance. Adv Energy Mater, 2015, 5: 1501065 CrossRef Google Scholar

[26] Scholz S, Kondakov D, Lüssem B, et al. Degradation mechanisms and reactions in organic light-emitting devices. Chem Rev, 2015, 115: 8449-8503 CrossRef PubMed Google Scholar

[27] Nikolka M, Schweicher G, Armitage J, et al. Performance improvements in conjugated polymer devices by removal of water-induced traps. Adv Mater, 2018, 30: 1801874 CrossRef PubMed Google Scholar

[28] Gomes HL, Stallinga P, Cölle M, et al. Electrical instabilities in organic semiconductors caused by trapped supercooled water. Appl Phys Lett, 2006, 88: 082101 CrossRef ADS Google Scholar

[29] Tsai MJ, Meng HF. Electron traps in organic light-emitting diodes. J Appl Phys, 2005, 97: 114502 CrossRef ADS Google Scholar

[30] Nikolka M, Broch K, Armitage J, et al. High-mobility, trap-free charge transport in conjugated polymer diodes. Nat Commun, 2019, 10: 2122 CrossRef PubMed ADS Google Scholar

[31] Nikolka M, Nasrallah I, Rose B, et al. High operational and environmental stability of high-mobility conjugated polymer field-effect transistors through the use of molecular additives. Nat Mater, 2017, 16: 356-362 CrossRef PubMed ADS Google Scholar

[32] Sun R, Wu Q, Guo J, et al. A layer-by-layer architecture for printable organic solar cells overcoming the scaling lag of module efficiency. Joule, 2020, 4: 407-419 CrossRef Google Scholar

[33] Sun R, Deng D, Guo J, et al. Spontaneous open-circuit voltage gain of fully fabricated organic solar cells caused by elimination of interfacial energy disorder. Energy Environ Sci, 2019, 12: 2518-2528 CrossRef Google Scholar

[34] Sun R, Guo J, Sun C, et al. A universal layer-by-layer solution-processing approach for efficient non-fullerene organic solar cells. Energy Environ Sci, 2019, 12: 384-395 CrossRef Google Scholar

[35] Wang W, Wu Q, Sun R, et al. Controlling molecular mass of low-band-gap polymer acceptors for high-performance all-polymer solar cells. Joule, 2020, 4: 1070-1086 CrossRef Google Scholar

[36] Min J, Güldal NS, Guo J, et al. Gaining further insight into the effects of thermal annealing and solvent vapor annealing on time morphological development and degradation in small molecule solar cells. J Mater Chem A, 2017, 5: 18101-18110 CrossRef Google Scholar

[37] Gurney RS, Lidzey DG, Wang T. A review of non-fullerene polymer solar cells: From device physics to morphology control. Rep Prog Phys, 2019, 82: 036601 CrossRef PubMed ADS Google Scholar

[38] Zhao F, Wang C, Zhan X. Morphology control in organic solar cells. Adv Energy Mater, 2018, 8: 1703147 CrossRef Google Scholar

[39] Huang Y, Kramer EJ, Heeger AJ, et al. Bulk heterojunction solar cells: Morphology and performance relationships. Chem Rev, 2014, 114: 7006-7043 CrossRef PubMed Google Scholar

[40] Zhang M, Guo X, Ma W, et al. A large-bandgap conjugated polymer for versatile photovoltaic applications with high performance. Adv Mater, 2015, 27: 4655-4660 CrossRef PubMed Google Scholar

[41] Yuan J, Zhang Y, Zhou L, et al. Single-junction organic solar cell with over 15% efficiency using fused-ring acceptor with electron-deficient core. Joule, 2019, 3: 1140-1151 CrossRef Google Scholar

[42] Min J, Kwon OK, Cui C, et al. High performance all-small-molecule solar cells: Engineering the nanomorphology via processing additives. J Mater Chem A, 2016, 4: 14234-14240 CrossRef Google Scholar

[43] Yu R, Yao H, Hong L, et al. Design and application of volatilizable solid additives in non-fullerene organic solar cells. Nat Commun, 2018, 9: 4645 CrossRef PubMed ADS Google Scholar

[44] Nicolai HT, Mandoc MM, Blom PWM. Electron traps in semiconducting polymers: Exponential versus Gaussian trap distribution. Phys Rev B, 2011, 83: 195204 CrossRef ADS Google Scholar

[45] Zuo G, Li Z, Andersson O, et al. Molecular doping and trap filling in organic semiconductor host-guest systems. J Phys Chem C, 2017, 121: 7767-7775 CrossRef Google Scholar

[46] Mandoc MM, de Boer B, Paasch G, et al. Trap-limited electron transport in disordered semiconducting polymers. Phys Rev B, 2007, 75: 193202 CrossRef ADS Google Scholar

[47] Min J, Jiao X, Sgobba V, et al. High efficiency and stability small molecule solar cells developed by bulk microstructure fine-tuning. Nano Energy, 2016, 28: 241-249 CrossRef Google Scholar

[48] Min J, Luponosov YN, Gasparini N, et al. Effects of alkyl terminal chains on morphology, charge generation, transport, and recombination mechanisms in solution-processed small molecule bulk heterojunction solar cells. Adv Energy Mater, 2015, 5: 1500386 CrossRef Google Scholar

[49] Karki A, Vollbrecht J, Gillett AJ, et al. The role of bulk and interfacial morphology in charge generation, recombination, and extraction in non-fullerene acceptor organic solar cells. Energy Environ Sci, 2020, 13: 3679-3692 CrossRef Google Scholar

[50] Vollbrecht J, Brus VV, Ko SJ, et al. Quantifying the nongeminate recombination dynamics in nonfullerene bulk heterojunction organic solar cells. Adv Energy Mater, 2019, 9: 1901438 CrossRef Google Scholar

[51] Brus VV, Proctor CM, Ran NA, et al. Capacitance spectroscopy for quantifying recombination losses in nonfullerene small-molecule bulk heterojunction solar cells. Adv Energy Mater, 2016, 6: 1502250 CrossRef Google Scholar

[52] Albrecht S, Tumbleston JR, Janietz S, et al. Quantifying charge extraction in organic solar cells: The case of fluorinated PCPDTBT. J Phys Chem Lett, 2014, 5: 1131-1138 CrossRef PubMed Google Scholar

[53] Proctor CM, Kim C, Neher D, et al. Nongeminate recombination and charge transport limitations in diketopyrrolopyrrole-based solution-processed small molecule solar cells. Adv Funct Mater, 2013, 23: 3584-3594 CrossRef Google Scholar

[54] Karki A, Vollbrecht J, Dixon AL, et al. Understanding the high performance of over 15% efficiency in single-junction bulk heterojunction organic solar cells. Adv Mater, 2019, 31: 1903868 CrossRef PubMed Google Scholar

[55] Zhu W, Spencer AP, Mukherjee S, et al. Crystallography, morphology, electronic structure, and transport in non-fullerene/non-indacenodithienothiophene polymer: Y6 solar cells. J Am Chem Soc, 2020, 142: 14532-14547 CrossRef PubMed Google Scholar

[56] Heiber MC, Okubo T, Ko SJ, et al. Measuring the competition between bimolecular charge recombination and charge transport in organic solar cells under operating conditions. Energy Environ Sci, 2018, 11: 3019-3032 CrossRef Google Scholar

[57] Bartesaghi D, Pérez IDC, Kniepert J, et al. Competition between recombination and extraction of free charges determines the fill factor of organic solar cells. Nat Commun, 2015, 6: 1 CrossRef PubMed ADS Google Scholar

[58] Wang T, Sun R, Xu S, et al. A wide-bandgap D-A copolymer donor based on a chlorine substituted acceptor unit for high performance polymer solar cells. J Mater Chem A, 2019, 7: 14070-14078 CrossRef Google Scholar

[59] Yang W, Guo J, Sun R, et al. Finely tuned cores in star-shaped zwitterionic molecules for interface engineering of high-performance polymer solar cells. Sol RRL, 2019, 3: 1900166 CrossRef Google Scholar

[60] Sun R, Wu Y, Guo J, et al. High-efficiency all-small-molecule organic solar cells based on an organic molecule donor with an asymmetric thieno[2,3-f] benzofuran unit. Sci China Chem, 2020, 63: 1246-1255 CrossRef Google Scholar

[61] Wang C, Zhang X, Hu W. Organic photodiodes and phototransistors toward infrared detection: Materials, devices, and applications. Chem Soc Rev, 2020, 49: 653-670 CrossRef PubMed Google Scholar

[62] Xiao X, Pan G, Li T, et al. Magnetic-field guided solvent vapor annealing for enhanced molecular alignment and carrier mobility of a semiconducting diketopyrrolopyrrole-based polymer. J Mater Chem C, 2020, 8: 4477-4485 CrossRef Google Scholar

  • 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) (%)

    AR-CF

    0.833

    25.39

    24.57

    72.11

    15.25 (14.97b)

    HPLC-CF

    0.833

    25.41

    24.74

    74.79

    15.83 (15.59b)

    SWEc

    0.833

    25.99

    25.21

    78.98

    17.10 (16.73b)

    SWE (AR-CF)

    0.832

    25.59

    24.81

    74.14

    15.79 (15.46d)

    SWE (HPLC-CF)

    0.836

    25.77

    25.04

    75.84

    (15.81d)

    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

    Processing

    conditions

    Hole-only devices

    Electron-only devices

    µh/µe

    Solar cells

    Mobility (×10−4

    cm2 V−1 s−1)

    Nt

    (×1023 m−3)

    Et

    (eV)

    σDOS

    (eV)

    Mobility (×10−4

    cm2 V−1 s−1)

    Nt

    (×1023 m−3)

    Et

    (eV)

    σDOS

    (eV)

    R

    τ1a

    (μs)

    τ2b

    (μs)

    CF (AR)

    1.346

    2.359

    0.375

    0.140

    1.222

    2.553

    0.377

    0.141

    1.10

    2.17

    3.83

    0.393

    CF (HPLC)

    1.380

    2.311

    0.374

    0.140

    1.335

    2.373

    0.375

    0.140

    1.03

    2.14

    3.65

    0.369

    SWE

    1.468

    2.196

    0.373

    0.140

    1.503

    2.150

    0.372

    0.140

    0.98

    2.06

    2.86

    0.326

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

qqqq

Contact and support