VIEWS & COMMENTS

Bright future of polymerizing small-molecule acceptors in realizing high performance all-polymer solar cells

  • Qi Chen 1 ,
  • Cen Zhang 1 ,
  • Lingwei Xue 1,2 ,
  • Zhi-Guo Zhang , 1
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  • 1. State Key Laboratory of Chemical Resource Engineering, Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China
  • 2. School of Chemical and Environmental Engineering, Pingdingshan University, Pingdingshan 467000, China

Received date: 31 Dec 2021

Accepted date: 27 Jan 2022

Published date: 17 Oct 2022

Copyright

2022 Higher Education Press

Cite this article

Qi Chen , Cen Zhang , Lingwei Xue , Zhi-Guo Zhang . Bright future of polymerizing small-molecule acceptors in realizing high performance all-polymer solar cells[J]. Frontiers of Chemical Science and Engineering, 2022 , 16(10) : 1526 -1529 . DOI: 10.1007/s11705-022-2161-3

All-polymer solar cells (all-PSCs) are prepared with a sandwich device structure based on a binary blend of a polymer donor and a polymer acceptor (Fig.1), and have attracted intensive research attention as a potential renewable photovoltaic technology [1,2]. As compared to the PSCs with small molecule acceptors (SMAs), all-PSCs show pronounced advantages of superior mechanical flexibility/stretchability and improved device stability [3,4]. Thus, they are more attractive for the applications in wearable and portable electronics. After the first report of the all-PSCs in 1995 using cyano-substituted polyphenylenevinylene as the polymer acceptor [5,6], researchers have focused their efforts on the design of new polymer acceptors, such as rylenediimide [7], B←N bridged bipyridine [8], and cyanobenzothiadiazole-based polymer acceptors [9]. However, before 2017, the power conversion efficiency (PCE) of the all-PSCs was limited by the weak absorbance of the polymer acceptors in the near-infrared region [10].
Fig.1 (a) Device structure of all-PSCs; (b) schematic illustration of the strategy of PSMA along with (c–e) the building blocks used to construct PSMAs; (f) typical polymer donors that working well with PSMAs.

Full size|PPT slide

In 2017, Zhang et al. [11] from Institute of Chemistry, Chinese Academy of Sciences proposed a strategy of polymerizing small-molecule acceptors (PSMAs) to construct new-generation polymer acceptors with narrow-band-gap SMAs as the key building blocks copolymerized with different aromatic linking units (Fig.1(b)). This strategy can inherit the merits of strong absorption from SMAs and potential advantages of good film forming ability, mechanical flexibility and high stability for polymers [2]. Thus, PSMAs hold tremendous potential for all-PSCs, and most importantly, it breaks the major bottleneck limiting all-PSCs, i.e., poor absorptivity in the near-infrared region [1].
Inspired by the advantages of PSMAs, intensive works from different groups on designing new PSMAs were carried out, and great progress has been made in the all-PSCs. Generally, the PSMAs are designed with an A-D-A or A-DA’D-A SMA backbone (see Fig.1(c, d)) copolymerized with a suitable conjugated linking unit (see Fig.1(e)). For example, the extension of the conjugation of central D-unit of the SMA from tetracyclic core to pentacyclic core, usually results in the PSMAs with slightly red-shifted absorption for a broad photo responsive range [12]. Notably, the success of the A-DA’D-A type Y6 and its derivatives as SMAs in PSCs [1315], also triggered their use as building blocks to construct efficient PSMAs [1619]. By replacing the common used linking unit of thiophene with benzodithiophene, bithiophene, selenophene [19], bridged BT and flexible chain tethered thiophene, photophophycial properties of the PSMAs can be tuned. It is worth noting that the using of electron-deficient bithiophene imide, producing PSMAs with improved n-type characteristics and suitable low-lying frontier molecular orbital levels [20]. Despite the remarkable progress, regioisomeric issue of the polymer chain is a limitation for a higher device efficiency. Regioregular PSMA can be obtained by carefully purifying the SMAs terminal A unit, producing improved crystallinity and electron mobility of the polymer acceptors thus higher device efficiency [2123]. The photovoltaic performance of the PSMAs can also be improved by molecular weight control of donors, stepwise optimization strategy and ternary blend. Notably, the ternary blend approach has resulted in the first example of the all-PSCs with efficiency over 17% [24]. Moreover, flexible all-PSCs are also constructed, showing excellent morphological and mechanical stabilities [25]. With these encouraging results, it is believed that higher device efficiency over 18% can be realized by constructing flexible PSMA-based all-PSCs. Also, the followings are suggestions for realizing real application of the PSMA-based all-PSCs.
(1) The design of PSMAs with a simple structure is greatly desirable to reduce the cost of their production. Previous studies highlighted the important role of proper molecular weights of PSMAs in achieving high-efficiency all-PSCs. Thus, it is also desirable to develop greener and more effective synthetic routes to well control the molecular weights of PSMAs. In general, the molecular structural diversity of polymer donors can provide more choices for device fabrication. In the PSMA-based all-PSCs, only a very few polymer donors are available. Typical examples are provided in Fig.1(f), including benzodithiophenedione-based polymers (PM6 and PBDB-T), quinoxaline-based polymers (PTQ10 and PBQx-H-TF) [26,27], imide based polymers (Q4 and PTzBI-oF) [28,29] and benzothiadiazole based polymers (D18 and JD40) [30,31]. In addition, the pairing of the benzotriazole based polymer donors [32] with those newly developed PSMAs is also very appealing to further increase their photovoltaic properties. Therefore, it is challenging and appealing to construct new polymer donors that can work well with the PSMAs to realize higher PCEs.
(2) Single-component organic solar cells (SCOSCs) are under investigation with advantages of high stability and reduced complexity in device fabrication. With a PSMA approach, Min [33] and Ma [34] independently construct block copolymer based SCOSCs via a stepwise stille coupling reaction, producing high efficiency in the range 9%‒11%. Higher morphological stability and lower energy loss were also observed in the reported SMOSC compared with the control binary blend devices. However, the performance of the state-of-the-art SCOSC still lags significantly behind that of binary organic solar cells. Thus, under a PSMA approach, a lot of further efforts are necessary to develop tailor-made block copolymers with optimized donor/acceptor couples for SCOSCs. To realize a highly ordered film, a certainly high molecular weight of the individual blocks and a narrow molecular weight distribution are preferred. However, it is a great synthetic challenge using conventional synthetic methods to control weight distribution, such as Stille coupling reaction.
(3) Besides efficiency, mechanical robustness is crucial for the practical applications of all-PSCs in stretchable and wearable electronics. However, seldom efforts are made on the investigation of the correlations between the chemical structure of PSMA and the mechanical stretchability in the all-PSC devices [35]. Exploration of new chemical approach to design PSMAs that can promote a high crack onset strain along with a suitable toughness in flexible device are highly desired.

Acknowledgements

The work was supported by the National Natural Science Foundation of China (Grant Nos. 22175014 and 21734008), the Fundamental Research Funds for the Central Universities (buctrc201822, XK1802-2).
1
Sun H, Guo X, Facchetti A. High-performance n-type polymer semiconductors: applications, recent development, and challenges. Chem, 2020, 6( 6): 1310– 1326

DOI

2
Zhang Z G, Li Y. Polymerized small molecule acceptors for high performance all-polymer solar cells. Angewandte Chemie International Edition, 2021, 60( 9): 4422– 4433

DOI

3
Wang G, Melkonyan F S, Facchetti A, Marks T J. All-polymer solar cells: recent progress, challenges, and prospects. Angewandte Chemie International Edition, 2019, 58( 13): 4129– 4142

DOI

4
Kang H, Lee W, Oh J, Kim T, Lee C, Kim B J. From fullerene-polymer to all-polymer solar cells: the importance of molecular packing, orientation, and morphology control. Accounts of Chemical Research, 2016, 49( 11): 2424– 2434

DOI

5
Yu G, Heeger A J. Charge separation and photovoltaic conversion in polymer composites with internal donor/acceptor heterojunctions. Journal of Applied Physics, 1995, 78( 7): 4510– 4515

DOI

6
Halls J J M, Walsh C A, Greenham N C, Marseglia E A, Friend R H, Moratti S C, Holmes A B. Efficient photodiodes from interpenetrating polymer networks. Nature, 1995, 376( 6540): 498– 500

DOI

7
Zhan X, Tan Z, Domercq B, An Z, Zhang X, Barlow S, Li Y, Zhu D, Kippelen B, Marder S R. A high-mobility electron-transport polymer with broad absorption and its use in field-effect transistors and all-polymer solar cells. Journal of the American Chemical Society, 2007, 129( 23): 7246– 7247

DOI

8
Zhao R, Liu J, Wang L. Polymer acceptors containing B←N units for organic photovoltaics. Accounts of Chemical Research, 2020, 53( 8): 1557– 1567

DOI

9
Shi S, Chen P, Chen Y, Feng K, Liu B, Chen J, Liao Q, Tu B, Luo J, Su M. . A narrow-bandgap n-type polymer semiconductor enabling efficient all-polymer solar cells. Advanced Materials, 2019, 31( 46): 1905161

DOI

10
Gao L, Zhang Z G, Xue L, Min J, Zhang J, Wei Z, Li Y. All-polymer solar cells based on absorption-complementary polymer donor and acceptor with high power conversion efficiency of 8.27%. Advanced Materials, 2016, 28( 9): 1884– 1890

DOI

11
Zhang Z G, Yang Y, Yao J, Xue L, Chen S, Li X, Morrison W, Yang C, Li Y. Constructing a strongly absorbing low-bandgap polymer acceptor for high-performance all-polymer solar cells. Angewandte Chemie International Edition, 2017, 56( 43): 13503– 13507

DOI

12
Wu J, Meng Y, Guo X, Zhu L, Liu F, Zhang M. All-polymer solar cells based on a novel narrow-bandgap polymer acceptor with power conversion efficiency over 10%. Journal of Materials Chemistry A, 2019, 7( 27): 16190– 16196

DOI

13
Yuan J, Zhang Y, Zhou L, Zhang G, Yip H L, Lau T K, Lu X, Zhu C, Peng H, Johnson P A. . Single-junction organic solar cell with over 15% efficiency using fused-ring acceptor with electron-deficient core. Joule, 2019, 3( 4): 1140– 1151

DOI

14
Yuan J, Huang T, Cheng P, Zou Y, Zhang H, Yang J L, Chang S Y, Zhang Z, Huang W, Wang R. . Enabling low voltage losses and high photocurrent in fullerene-free organic photovoltaics. Nature Communications, 2019, 10( 1): 570

DOI

15
Zhu C, Yuan J, Cai F, Meng L, Zhang H, Chen H, Li J, Qiu B, Peng H, Chen S. . Tuning the electron-deficient core of a non-fullerene acceptor to achieve over 17% efficiency in a single-junction organic solar cell. Energy & Environmental Science, 2020, 13( 8): 2459– 2466

DOI

16
Jia T, Zhang J, Zhong W, Liang Y, Zhang K, Dong S, Ying L, Liu F, Wang X, Huang F. . 14.4% efficiency all-polymer solar cell with broad absorption and low energy loss enabled by a novel polymer acceptor. Nano Energy, 2020, 72 : 104718

DOI

17
Wang W, Wu Q, Sun R, Guo J, Wu Y, Shi M, Yang W, Li H, Min J. Controlling molecular mass of low-band-gap polymer acceptors for high-performance all-polymer solar cells. Joule, 2020, 4( 5): 1070– 1086

DOI

18
Du J, Hu K, Meng L, Angunawela I, Zhang J, Qin S, Liebman-Pelaez A, Zhu C, Zhang Z, Ade H. . High performance all-polymer solar cells with the polymer acceptor synthesized via a random ternary copolymerization strategy. Angewandte Chemie International Edition, 2020, 59( 35): 15181– 15185

DOI

19
Du J, Hu K, Zhang J, Meng L, Yue J, Angunawela I, Yan H, Qin S, Kong X, Zhang Z. . Polymerized small molecular acceptor based all-polymer solar cells with an efficiency of 16.16% via tuning polymer blend morphology by molecular design. Nature Communications, 2021, 12( 1): 5264

DOI

20
Sun H, Yu H, Shi Y, Yu J, Peng Z, Zhang X, Liu B, Wang J, Singh R, Lee J. . A narrow-bandgap n-type polymer with an acceptor-acceptor backbone enabling efficient all-polymer solar cells. Advanced Materials, 2020, 32( 43): 2004183

DOI

21
Fu H, Li Y, Yu J, Wu Z, Fan Q, Lin F, Woo H Y, Gao F, Zhu Z, Jen A K Y. High efficiency (15.8%) all-polymer solar cells enabled by a regioregular narrow bandgap polymer acceptor. Journal of the American Chemical Society, 2021, 143( 7): 2665– 2670

DOI

22
Luo Z, Liu T, Ma R, Xiao Y, Zhan L, Zhang G, Sun H, Ni F, Chai G, Wang J. . Precisely controlling the position of bromine on the end group enables well-regular polymer acceptors for all-polymer solar cells with efficiencies over 15%. Advanced Materials, 2020, 32( 48): 2005942

DOI

23
Yu H, Pan M, Sun R, Agunawela I, Zhang J, Li Y, Qi Z, Han H, Zou X, Zhou W. . Regio-regular polymer acceptors enabled by determined fluorination on end groups for all-polymer solar cells with 15.2% efficiency. Angewandte Chemie International Edition, 2021, 60( 18): 10137– 10146

DOI

24
Sun R, Wang W, Yu H, Chen Z, Xia X, Shen H, Guo J, Shi M, Zheng Y, Wu Y. . Achieving over 17% efficiency of ternary all-polymer solar cells with two well-compatible polymer acceptors. Joule, 2021, 5( 6): 1548– 1565

DOI

25
Genene Z, Lee J W, Lee S W, Chen Q, Tan Z, Abdulahi B A, Yu D, Kim T S, Kim B J, Wang E. Polymer acceptors with flexible spacers afford efficient and mechanically robust all-polymer solar cells. Advanced Materials, 2022, 34( 6): 2107361

DOI

26
Sun C, Pan F, Bin H, Zhang J, Xue L, Qiu B, Wei Z, Zhang Z G, Li Y. A low cost and high performance polymer donor material for polymer solar cells. Nature Communications, 2018, 9( 1): 743

DOI

27
Zhao T, Cao C, Wang H, Shen X, Lai H, Zhu Y, Chen H, Han L, Rehman T, He F. Highly efficient all-polymer solar cells from a dithieno[3,2-f:2′,3′-h]quinoxaline-based wide band gap donor. Macromolecules, 2021, 54( 24): 11468– 11477

DOI

28
Peng F, An K, Zhong W, Li Z, Ying L, Li N, Huang Z, Zhu C, Fan B, Huang F. . A universal fluorinated polymer acceptor enables all-polymer solar cells with >15% efficiency. ACS Energy Letters, 2020, 5( 12): 3702– 3707

DOI

29
Shi Y, Ma R, Wang X, Liu T, Li Y, Fu S, Yang K, Wang Y, Yu C, Jiao L. . Influence of fluorine substitution on the photovoltaic performance of wide band gap polymer donors for polymer solar cells. ACS Applied Materials & Interfaces, 2022, 14( 4): 5740– 5749

DOI

30
Jia T, Zhang J, Zhang K, Tang H, Dong S, Tan C H, Wang X, Huang F. All-polymer solar cells with efficiency approaching 16% enabled using a dithieno[3′,2′:3,4;2′′,3′′:5,6]benzo[1,2-c][1,2,5]thiadiazole (fDTBT)-based polymer donor. Journal of Materials Chemistry A, 2021, 9( 14): 8975– 8983

DOI

31
Liu Q, Jiang Y, Jin K, Qin J, Xu J, Li W, Xiong J, Liu J, Xiao Z, Sun K. . 18% efficiency organic solar cells. Science Bulletin, 2020, 65( 4): 272– 275

DOI

32
Zhang Z G, Bai Y, Li Y. Benzotriazole based 2d-conjugated polymer donors for high performance polymer solar cells. Chinese Journal of Polymer Science, 2021, 39( 1): 1– 13

DOI

33
Wu Y, Guo J, Wang W, Chen Z, Chen Z, Sun R, Wu Q, Wang T, Hao X, Zhu H. . A conjugated donor-acceptor block copolymer enables over 11% efficiency for single-component polymer solar cells. Joule, 2021, 5( 7): 1800– 1815

DOI

34
Li S, Yuan X, Zhang Q, Li B, Li Y, Sun J, Feng Y, Zhang X, Wu Z, Wei H. . Narrow-bandgap single-component polymer solar cells with approaching 9% efficiency. Advanced Materials, 2021, 33( 32): 2101295

DOI

35
Fan Q, Su W, Chen S, Kim W, Chen X, Lee B, Liu T, Méndez-Romero U A, Ma R, Yang T. . Mechanically robust all-polymer solar cells from narrow band gap acceptors with hetero-bridging atoms. Joule, 2020, 4( 3): 658– 672

DOI

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