logo

Environmentally-friendly solvent processed fullerene-free organic solar cells enabled by screening halogen-free solvent additives

More info
  • ReceivedJun 3, 2017
  • AcceptedJul 20, 2017
  • PublishedAug 7, 2017

Abstract

Though the power conversion efficiencies (PCEs) of organic solar cells (OSCs) have been boosted to 12%, the use of highly pollutive halogenated solvents as the processing solvent significantly hinders the mass production of OSCs. It is thus necessary to achieve high-efficiency OSCs by utilizing the halogen-free and environmentally-friendly solvents. Herein, we applied a halogen-free solvent system (o-xylene/1-phenylnaphthalene, XY/PN) for fabricating fullerene-free OSCs, and a high PCE of 11.6% with a notable fill factor (FF) of 72% was achieved based on the PBDB-T:IT-M blend, which is among the top efficiencies of halogen-free solvent processed OSCs. In addition, the influence of different halogen-free solvent additives on the blend morphology and device performance metrics was studied by synchrotron-based tools and other complementary methods. Morphological results indicate the highly ordered molecular packing and highest average domain purity obtained in the blend films prepared by using XY/PN co-solvent are favorable for achieving increased FFs and thus higher PCEs in the devices. Moreover, a lower interaction parameter (χ) of the IT-M:PN pair provides a good explanation for the more favorable morphology and performance in devices with PN as the solvent additive, relative to those with diphenyl ether and N-methylpyrrolidone. Our study demonstrates that carefully screening the non-halogenated solvent additive plays a vital role in realizing the efficient and environmentally-friendly solvent processed OSCs.


Funded by

National Natural Science Foundation of China(91333204,21325419,51673201)

Chinese Academy of Sciences(XDB12030200,KJZD-EW-J01)

National Basic Research Program 973(2014CB643501)

CAS-Croucher Funding Scheme for Joint Laboratories(CAS14601)

US Office of Naval Research(ONR)

US Department of Energy(DE-AC02-05CH11231)


Acknowledgment

The authors acknowledge the financial support from the National Natural Science Foundation of China (91333204, 21325419 and 51673201), the Chinese Academy of Sciences (XDB12030200, KJZD-EW-J01), the National Basic Research Program 973 (2014CB643501), and the CAS-Croucher Funding Scheme for Joint Laboratories (CAS14601). GIWAXS/R-SoXS and solubility parameter analysis by Ye L and Ade H were supported by the US Office of Naval Research (ONR) grant N00141512322. DSC data and analysis by Ghasemi M were supported by a Research Opportunity Initiative grant by the UNC General Administatrtion. X-ray data were acquired at beamlines 11.0.1.2, and 7.3.3 at Advanced Light Source, which is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the US Department of Energy under Contract No. DE-AC02-05CH11231. Jiao X, Awartani O and Carpenter J are acknowledged for taking part of the R-SoXS data. Zhu C and Wang C are appreciated for the beamline support.


Interest statement

The authors declare that they have no conflict of interest.


Contributions statement

Zhao W fabricated and optimized the devices; Li S synthesized the nonfullerene acceptor IT-M; Zhang S synthesized PBDB-T; Liu X and Zhang Y carried out the AFM characterizations. Ye L collected and analysed the R-SoXS and GIWAXS data; Ghasemi M did the DSC measurements; He C provided the solvents and additives; Hou J and Ade H supervised the study; all authors commented on the final paper.


Author information

Wenchao Zhao received his MSc degree in materials physics and chemistry from Ocean University of China in 2015. Now he is a PhD candidate under the supervision of Prof. Jianhui Hou at the Institute of Chemistry, Chinese Academy of Sciences (ICCAS). His research interests are focused on interfacial engineering and morphology in high-efficiency organic solar cells.


Long Ye is a postdoctoral research associate working with Prof. Harald Ade at the Department of Physics, North Carolina State University (NCSU), USA. He received his PhD degree in 2015 at the ICCAS under the direction of Prof. Jianhui Hou. His research focuses on developing high-efficiency (printed) organic solar cells and characterizing, manipulating, and predicting the complex morphology of organic/polymeric blends in photovoltaic devices using soft X-ray scattering/microscopy and differential scanning calorimetry.


Harald Ade is a Distinguished Professor of Physics and Director of ORaCEL at NCSU. He received his PhD degree in physics from State University of New York at Stony Brook (now Stony Brook University) in 1990 and has been a faculty member at NCSU since 1992. He is developing and using novel soft X-ray characterization tools (microscopy, scattering, reflectivity, etc.), with a focus on the characterization of organic devices.


Jianhui Hou received his PhD degree in chemistry from the ICCAS in 2006 (Advisor: Prof. Yongfang Li). Then he joined Prof. Yang Yang’s Group at the University of California, Los Angeles, as a postdoctoral researcher. Since 2010, he became a professor at ICCAS, where he leads a group of organic solar cell materials and devices. He has published more than 200 papers, including Nat. Photonics, Chem. Rev., J. Am. Chem. Soc., Angew. Chem. In. Ed., Adv. Mater.


Supplement

Supplementary information

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


References

[1] Li G, Zhu R, Yang Y. Polymer solar cells. Nat Photon, 2012, 6: 153-161 CrossRef ADS Google Scholar

[2] Li Y. Molecular design of photovoltaic materials for polymer solar cells: toward suitable electronic energy levels and broad absorption. Acc Chem Res, 2012, 45: 723-733 CrossRef PubMed Google Scholar

[3] Muccini M. A bright future for organic field-effect transistors. Nat Mater, 2006, 5: 605-613 CrossRef PubMed ADS Google Scholar

[4] Mei J, Diao Y, Appleton AL, et al. Integrated materials design of organic semiconductors for field-effect transistors. J Am Chem Soc, 2013, 135: 6724-6746 CrossRef PubMed Google Scholar

[5] Müller CD, Falcou A, Reckefuss N, et al. Multi-colour organic light-emitting displays by solution processing. Nature, 2003, 421: 829-833 CrossRef PubMed ADS Google Scholar

[6] Halim H, Guo Y. Flexible organic-inorganic hybrid perovskite solar cells. Sci China Mater, 2016, 59: 495-506 CrossRef Google Scholar

[7] Ye L, Zhang S, Huo L, et al. Molecular design toward highly efficient photovoltaic polymers based on two-dimensional conjugated benzodithiophene. Acc Chem Res, 2014, 47: 1595-1603 CrossRef PubMed Google Scholar

[8] Liu F, Gu Y, Shen X, et al. Characterization of the morphology of solution-processed bulk heterojunction organic photovoltaics. Prog Polymer Sci, 2013, 38: 1990-2052 CrossRef Google Scholar

[9] 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

[10] Liu Y, Zhao J, Li Z, et al. Aggregation and morphology control enables multiple cases of high-efficiency polymer solar cells. Nat Commun, 2014, 5: 5293 CrossRef PubMed ADS Google Scholar

[11] Zhang S, Ye L, Zhao W, et al. Realizing over 10% efficiency in polymer solar cell by device optimization. Sci China Chem, 2015, 58: 248-256 CrossRef Google Scholar

[12] Li M, Gao K, Wan X, et al. Solution-processed organic tandem solar cells with power conversion efficiencies >12%. Nat Photon, 2016, 11: 85-90 CrossRef Google Scholar

[13] Huang J, Carpenter JH, Li CZ, et al. Highly efficient organic solar cells with improved vertical donor-acceptor compositional gradient via an inverted off-center spinning method. Adv Mater, 2016, 28: 967-974 CrossRef PubMed Google Scholar

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

[15] Zhao W, Ye L, Zhang S, et al. A universal halogen-free solvent system for highly efficient polymer solar cells. J Mater Chem A, 2015, 3: 12723-12729 CrossRef Google Scholar

[16] Fan B, Ying L, Wang Z, et al. Optimisation of processing solvent and molecular weight for the production of green-solvent-processed all-polymer solar cells with a power conversion efficiency over 9%. Energ Environ Sci, 2017, 10: 1243-1251 CrossRef Google Scholar

[17] Lin Y, Zhan X. Non-fullerene acceptors for organic photovoltaics: an emerging horizon. Mater Horiz, 2014, 1: 470-488 CrossRef Google Scholar

[18] Zhang ZG, Li Y. Side-chain engineering of high-efficiency conjugated polymer photovoltaic materials. Sci China Chem, 2015, 58: 192-209 CrossRef Google Scholar

[19] Nielsen CB, Holliday S, Chen HY, et al. Non-fullerene electron acceptors for use in organic solar cells. Acc Chem Res, 2015, 48: 2803-2812 CrossRef PubMed Google Scholar

[20] Yao H, Ye L, Zhang H, et al. Molecular design of benzodithiophene-based organic photovoltaic materials. Chem Rev, 2016, 116: 7397-7457 CrossRef PubMed Google Scholar

[21] Lu L, Zheng T, Wu Q, et al. Recent advances in bulk heterojunction polymer solar cells. Chem Rev, 2015, 115: 12666-12731 CrossRef PubMed Google Scholar

[22] Yip HL, Jen AKY. Recent advances in solution-processed interfacial materials for efficient and stable polymer solar cells. Energ Environ Sci, 2012, 5: 5994 CrossRef Google Scholar

[23] Fan B, Zhang K, Jiang XF, et al. High-performance nonfullerene polymer solar cells based on imide-functionalized wide-bandgap polymers. Adv Mater, 2017, 29: 1606396 CrossRef PubMed Google Scholar

[24] Zhang G, Zhang K, Yin Q, et al. High-performance ternary organic solar cell enabled by a thick active layer containing a liquid crystalline small molecule donor. J Am Chem Soc, 2017, 139: 2387-2395 CrossRef PubMed Google Scholar

[25] Zhao F, Dai S, Wu Y, et al. Single-junction binary-blend nonfullerene polymer solar cells with 12.1% efficiency. Adv Mater, 2017, 29: 1700144 CrossRef PubMed Google Scholar

[26] Lu H, Xu X, Bo Z. Perspective of a new trend in organic photovoltaic: ternary blend polymer solar cells. Sci China Mater, 2016, 59: 444-458 CrossRef Google Scholar

[27] Yao H, Ye L, Fan B, et al. Influence of the alkyl substitution position on photovoltaic properties of 2D-BDT-based conjugated polymers. Sci China Mater, 2015, 58: 213-222 CrossRef Google Scholar

[28] Bin H, Gao L, Zhang ZG, et al. 11.4% Efficiency non-fullerene polymer solar cells with trialkylsilyl substituted 2D-conjugated polymer as donor. Nat Commun, 2016, 7: 13651 CrossRef PubMed ADS Google Scholar

[29] Bin H, Zhong L, Zhang ZG, et al. Alkoxy substituted benzodithiophene-alt-fluorobenzotriazole copolymer as donor in non-fullerene polymer solar cells. Sci China Chem, 2016, 59: 1317-1322 CrossRef Google Scholar

[30] Zhang Z, Li M, Liu Y, et al. Simultaneous enhancement of the molecular planarity and the solubility of non-fullerene acceptors: effect of aliphatic side-chain substitution on the photovoltaic performance. J Mater Chem A, 2017, 5: 7776-7783 CrossRef Google Scholar

[31] Zhao W, Zhang S, Hou J. Realizing 11.3% efficiency in fullerene-free polymer solar cells by device optimization. Sci China Chem, 2016, 59: 1574-1582 CrossRef Google Scholar

[32] Lin Y, Zhan X. Oligomer molecules for efficient organic photovoltaics. Acc Chem Res, 2016, 49: 175-183 CrossRef PubMed Google Scholar

[33] Lin Y, Wang J, Zhang ZG, et al. An electron acceptor challenging fullerenes for efficient polymer solar cells. Adv Mater, 2015, 27: 1170-1174 CrossRef PubMed Google Scholar

[34] Lin Y, Zhang ZG, Bai H, et al. High-performance fullerene-free polymer solar cells with 6.31% efficiency. Energ Environ Sci, 2015, 8: 610-616 CrossRef Google Scholar

[35] Lin Y, He Q, Zhao F, et al. A facile planar fused-ring electron acceptor for as-cast polymer solar cells with 8.71% efficiency. J Am Chem Soc, 2016, 138: 2973-2976 CrossRef PubMed Google Scholar

[36] Lin Y, Zhao F, He Q, et al. High-performance electron acceptor with thienyl side chains for organic photovoltaics. J Am Chem Soc, 2016, 138: 4955-4961 CrossRef PubMed Google Scholar

[37] Wang W, Yan C, Lau T-K, et al. Fused hexacyclic nonfullerene acceptor with strong near-infrared absorption for semitransparent organic solar cells with 9.77% efficiency. Adv Mater, 2017, doi: 10.1002/adma.2017013081701308. Google Scholar

[38] Meng D, Sun D, Zhong C, et al. High-performance solution-processed non-fullerene organic solar cells based on selenophene-containing perylene bisimide acceptor. J Am Chem Soc, 2016, 138: 375-380 CrossRef PubMed Google Scholar

[39] Yang Y, Zhang ZG, Bin H, et al. Side-chain isomerization on an n-type organic semiconductor ITIC acceptor makes 11.77% high efficiency polymer solar cells. J Am Chem Soc, 2016, 138: 15011-15018 CrossRef PubMed Google Scholar

[40] Holliday S, Ashraf RS, Wadsworth A, et al. High-efficiency and air-stable P3HT-based polymer solar cells with a new non-fullerene acceptor. Nat Commun, 2016, 7: 11585 CrossRef PubMed ADS Google Scholar

[41] Li S, Ye L, Zhao W, et al. Energy-level modulation of small-molecule electron acceptors to achieve over 12% efficiency in polymer solar cells. Adv Mater, 2016, 28: 9423-9429 CrossRef PubMed Google Scholar

[42] Yao H, Cui Y, Yu R, et al. Design, synthesis, and photovoltaic characterization of a small molecular acceptor with an ultra-narrow band gap. Angew Chem Int Ed, 2017, 56: 3045-3049 CrossRef PubMed Google Scholar

[43] Dai S, Zhao F, Zhang Q, et al. Fused nonacyclic electron acceptors for efficient polymer solar cells. J Am Chem Soc, 2017, 139: 1336-1343 CrossRef PubMed Google Scholar

[44] Liu Y, Zhang Z, Feng S, et al. Exploiting noncovalently conformational locking as a design strategy for high performance fused-ring electron acceptor used in polymer solar cells. J Am Chem Soc, 2017, 139: 3356-3359 CrossRef PubMed Google Scholar

[45] Li S, Liu W, Li CZ, et al. A simple perylene diimide derivative with a highly twisted geometry as an electron acceptor for efficient organic solar cells. J Mater Chem A, 2016, 4: 10659-10665 CrossRef Google Scholar

[46] Zheng Z, Awartani OM, Gautam B, et al. Efficient charge transfer and fine-tuned energy level alignment in a THF-processed fullerene-free organic solar cell with 11.3% efficiency. Adv Mater, 2017, 29: 1604241 CrossRef PubMed Google Scholar

[47] Dayneko SV, Hendsbee AD, Welch GC. Fullerene-free polymer solar cells processed from non-halogenated solvents in air with PCE of 4.8%. Chem Commun, 2017, 53: 1164-1167 CrossRef PubMed Google Scholar

[48] Ye L, Xiong Y, Yao H, et al. High performance organic solar cells processed by blade coating in air from a benign food additive solution. Chem Mater, 2016, 28: 7451-7458 CrossRef Google Scholar

[49] Ye L, Xiong Y, Li S, et al. Precise manipulation of multilength scale morphology and its influence on eco-friendly printed all-polymer solar cells. Adv Funct Mater, 2017, 48: 1702016 CrossRef Google Scholar

[50] Lou SJ, Szarko JM, Xu T, et al. Effects of additives on the morphology of solution phase aggregates formed by active layer components of high-efficiency organic solar cells. J Am Chem Soc, 2011, 133: 20661-20663 CrossRef PubMed Google Scholar

[51] Yao Y, Hou J, Xu Z, et al. Effects of solvent mixtures on the nanoscale phase separation in polymer solar cells. Adv Funct Mater, 2008, 18: 1783-1789 CrossRef Google Scholar

[52] Lee JK, Ma WL, Brabec CJ, et al. Processing additives for improved efficiency from bulk heterojunction solar cells. J Am Chem Soc, 2008, 130: 3619-3623 CrossRef PubMed Google Scholar

[53] Zhao W, Qian D, Zhang S, et al. Fullerene-free polymer solar cells with over 11% efficiency and excellent thermal stability. Adv Mater, 2016, 28: 4734-4739 CrossRef PubMed Google Scholar

[54] Ye L, Zhao W, Li S, et al. High-efficiency nonfullerene organic solar cells: critical factors that affect complex multi-length scale morphology and device performance. Adv Energ Mater, 2017, 7: 1602000 CrossRef Google Scholar

[55] Guo X, Cui C, Zhang M, et al. High efficiency polymer solar cells based on poly(3-hexylthiophene)/indene-C70 bisadduct with solvent additive. Energ Environ Sci, 2012, 5: 7943-7949 CrossRef Google Scholar

[56] Choi H, Ko SJ, Kim T, et al. Small-bandgap polymer solar cells with unprecedented short-circuit current density and high fill factor. Adv Mater, 2015, 27: 3318-3324 CrossRef PubMed Google Scholar

[57] Zhao W, Li S, Yao H, et al. Molecular optimization enables over 13% efficiency in organic solar cells. J Am Chem Soc, 2017, 139: 7148-7151 CrossRef PubMed Google Scholar

[58] Ye L, Zhou C, Meng H, et al. Toward reliable and accurate evaluation of polymer solar cells based on low band gap polymers. J Mater Chem C, 2015, 3: 564-569 CrossRef Google Scholar

[59] Hexemer A, Bras W, Glossinger J, et al. A SAXS/WAXS/GISAXS beamline with multilayer monochromator. J Phys-Conf Ser, 2010, 247: 012007 CrossRef ADS Google Scholar

[60] Gann E, Young AT, Collins BA, et al. Soft X-ray scattering facility at the advanced light source with real-time data processing and analysis. Rev Sci Instruments, 2012, 83: 045110-045110 CrossRef PubMed ADS Google Scholar

[61] Zhao W, Li S, Zhang S, et al. Ternary polymer solar cells based on two acceptors and one donor for achieving 12.2% efficiency. Adv Mater, 2017, 29: 1604059 CrossRef PubMed Google Scholar

[62] Wu JL, Chen FC, Hsiao YS, et al. Surface plasmonic effects of metallic nanoparticles on the performance of polymer bulk heterojunction solar cells. ACS Nano, 2011, 5: 959-967 CrossRef PubMed Google Scholar

[63] Bauer N, Zhang Q, Zhao J, et al. Comparing non-fullerene acceptors with fullerene in polymer solar cells: a case study with FTAZ and PyCNTAZ. J Mater Chem A, 2017, 5: 4886-4893 CrossRef Google Scholar

[64] Mukherjee S, Proctor CM, Tumbleston JR, et al. Importance of domain purity and molecular packing in efficient solution-processed small-molecule solar cells. Adv Mater, 2015, 27: 1105-1111 CrossRef PubMed Google Scholar

[65] Mukherjee S, Jiao X, Ade H. Charge creation and recombination in multi-length scale polymer:fullerene BHJ solar cell morphologies. Adv Energ Mater, 2016, 6: 1600699 CrossRef Google Scholar

[66] Ye L, Jiao X, Zhang S, et al. Control of mesoscale morphology and photovoltaic performance in diketopyrrolopyrrole-based small band gap terpolymers. Adv Energ Mater, 2017, 7: 1601138 CrossRef Google Scholar

[67] Leman D, Kelly MA, Ness S, et al. In situ characterization of polymer-fullerene bilayer stability. Macromolecules, 2015, 48: 383-392 CrossRef ADS Google Scholar

  • Figure 1

    (a) Chemical structures of polymer donor PBDB-T and non-fullerene acceptor IT-M. (b) Halogen-free host solvent o-xylene (XY) and three halogen-free solvent additives (DPE, NMP and PN). (c) The configurations of the regular and inverted devices used in this work. (d) Normalized absorption spectra of PBDB-T:IT-M blend film cast from XY, XY/DPE, XY/NMP and XY/PN.

  • Figure 2

    (a) J–V and (b) EQE curves of the optimized devices using XY and different solvent additives (DPE, NMP, and PN) as the co-solvent under AM 1.5 conditions, 100 mW cm−2; (c) photovoltaic parameters (PCE, Jsc, Voc, and FF) of PSCs processed using different solvent additives; (d) Jphversus Veff plots of the optimal devices processed using different solvent additives.

  • Figure 3

    AFM height (a–d) and phase (e–h) images of PBDB-B:IT-M blend films processed by XY, XY/DPE, XY/NMP and XY/PN, respectively.

  • Figure 4

    GIWAXS patterns of the blend films processed from (a) XY, (b) XY/DPE, (c) XY/NMP and (d) XY/PN, respectively.

  • Figure 5

    Thickness normalized and Lorentz-corrected R-SoXS profiles of (a) of the blend films processed from XY, XY/1% (vol) DPE, XY/1% (vol) NMP and XY/1% (vol) PN, respectively. (b) Plot of the relative ISI of the PBDB-T:IT-M based OSCs as a function of the solvent system.

  • Table 1   The photovoltaic parameters of PBDB-T:IT-M-based fullerene-free OSCs processed with different halogen-free solvents

    Solvents

    Voc

    (V)

    Jsc

    (mA cm−2)

    FF

    PCEmaxa)

    (%)

    PCEavgb)

    (%)

    XY

    0.940

    16.3

    0.543

    8.32

    7.98±0.23

    XY/DPE

    0.944

    16.5

    0.603

    9.39

    9.07±0.25

    XY/NMP

    0.949

    16.8

    0.657

    10.5

    10.0±0.39

    XY/PN

    0.948

    17.0

    0.703

    11.3

    10.9±0.35

    XY/PNc)

    0.942

    17.1

    0.721

    11.6

    11.3±0.21

Copyright 2020  CHINA SCIENCE PUBLISHING & MEDIA LTD.  中国科技出版传媒股份有限公司  版权所有

京ICP备14028887号-23       京公网安备11010102003388号