Recent progress in Prussian blue electrode for electrochromic devices

Abstract

Great progress has been made in the electrochromic (EC) technology with potential applications in various fields. As one of the most promising EC materials, Prussian blue (PB) has attracted great attention due to its excellent EC performance, such as low cost, easy synthesis, rich color states, chemical stability, suitable redox potential, and fast color-switching kinetics. This review summarizes the recent progress in PB electrodes and devices, including several typical preparation techniques of PB electrodes, as well as the recent key strategies for enhancing EC performance of PB electrodes. Specifically, PB-based electrochromic devices (ECDs) have been widely used in various fields, such as smart windows, electrochromic energy storage devices (EESDs), wearable electronics, smart displays, military camouflage, and other fields. Several opportunities and obstacles are suggested for advancing the development of PB-based ECDs. This comprehensive review is expected to offer valuable insights for the design and fabrication of sophisticated PB-based ECDs, enabling their practical integration into real-world applications.

Key words： Prussian blue; electrochromism; energy storage; smart windows

Acknowledgements

This work was supported by the Natural Science Foundation of Beijing Municipality, China (No. 2222045) and Beijing Nova Program, China (No. 20220484234).

Competing interests

The authors declare that they have no competing interests.

References

1 Lang A W, Li Y, De Keersmaecker M. . Transparent wood smart windows: Polymer electrochromic devices based on poly(3,4-ethylenedioxythiophene): Poly(styrene sulfonate) electrodes. ChemSusChem, 2018, 11(5): 854–863

2 Davy N C, Sezen-Edmonds M, Gao J. . Pairing of near-ultraviolet solar cells with electrochromic windows for smart management of the solar spectrum. Nature Energy, 2017, 2(8): 17104

3 Zhou Y, Dong X, Mi Y. . Hydrogel smart windows. Journal of Materials Chemistry. A, Materials for Energy and Sustainability, 2020, 8(20): 10007–10025

4 Wang K, Wu H, Meng Y. . Integrated energy storage and electrochromic function in one flexible device: An energy storage smart window. Energy & Environmental Science, 2012, 5(8): 8384–8389

5 Huang Y, Zhu M, Huang Y. . Multifunctional energy storage and conversion devices. Advanced Materials, 2016, 28(38): 8344–8364

6 Wang J, Zhang L, Yu L. . A bi-functional device for self-powered electrochromic window and self-rechargeable transparent battery applications. Nature Communications, 2014, 5(1): 4921

7 Liangmiao Z, Yi D, Fang X. . Two birds with one stone: A novel thermochromic cellulose hydrogel as electrolyte for fabricating electric-/thermal-dual-responsive smart windows. Chemical Engineering Journal, 2022, 455(2): 140849

8 Dong Sik K, Yong Hui L, Jung Wook K. . A stretchable array of high-performance electrochromic devices for displaying skin-attached multi-sensor signals. Chemical Engineering Journal, 2021, 429: 132289

9 Cai G, Wang J, Lee P S. Next-generation multifunctional electrochromic devices. Accounts of Chemical Research, 2016, 49(8): 1469–1476

10 Lei L, Chen L, Mengying W. . Low self-discharge all-solid-state electrochromic asymmetric supercapacitors at wide temperature toward efficient energy storage. Chemical Engineering Journal, 2022, 456: 141022

11 Ware M. Prussian blue: Artists’ pigment and chemists’ sponge. Journal of Chemical Education, 2008, 85(5): 612

12 Ludi A. Prussian blue, an inorganic evergreen. Journal of Chemical Education, 1981, 58(12): 1013

13 Ellis D, Eckhoff M, Neff V D. Electrochromism in the mixed-valence hexacyanides. 1. Voltammetric and spectral studies of the oxidation and reduction of thin films of Prussian blue. Journal of Physical Chemistry, 1981, 85(9): 1225–1231

14 Neff V D. Electrochemical oxidation and reduction of thin films of Prussian blue. Journal of the Electrochemical Society, 1978, 125(6): 886–887

15 Itaya K, Ataka T, Toshima S. Spectroelectrochemistry and electrochemical preparation method of Prussian blue modified electrodes. Journal of the American Chemical Society, 1982, 104(18): 4767–4772

16 Itaya K, Akahoshi H, Toshima S. Electrochemistry of Prussian blue modified electrodes: An electrochemical preparation method. Journal of the Electrochemical Society, 1982, 129(7): 1498–1500

17 Su D, Cortie M, Fan H. . Prussian blue nanocubes with an open framework structure coated with PEDOT as high-capacity cathodes for lithium–sulfur batteries. Advanced Materials, 2017, 29(48): 1700587

18 Wang R Y, Wessells C D, Huggins R A. . Highly reversible open framework nanoscale electrodes for divalent ion batteries. Nano Letters, 2013, 13(11): 5748–5752

19 DeLongchamp D M, Hammond P T. High-contrast electrochromism and controllable dissolution of assembled Prussian blue/polymer nanocomposites. Advanced Functional Materials, 2004, 14(3): 224–232

20 Jiao Z, Wang J, Ke L. . Electrochromic properties of nanostructured tungsten trioxide (hydrate) films and their applications in a complementary electrochromic device. Electrochimica Acta, 2012, 63: 153–160

21 Song J, Huang B, Liu S. . Facile preparation of Prussian blue electrochromic films for smart-supercapattery via an in-situ replacement reaction. Solar Energy, 2022, 232: 275–282

22 Li Z, Zhao Y, Xiao Y. . A feasible strategy of Prussian blue reflective electrochromic devices capable of reversible switching between sand-yellow and leaf-green. Materials Letters, 2022, 307: 130969

23 Li Z, Tang Y, Zhou K. . Improving electrochromic cycle life of Prussian blue by acid addition to the electrolyte. Materials, 2018, 12(1): 28

24 Stilwell D E, Park K H, Miles M H. Electrochemical studies of the factors influencing the cycle stability of Prussian blue films. Journal of Applied Electrochemistry, 1992, 22(4): 325–331

25 Wang K, Zhang H, Chen G. . Long-term-stable WO₃-PB complementary electrochromic devices. Journal of Alloys and Compounds, 2021, 861: 158534

26 Chaudhary A, Pathak D K, Ghosh T. . Prussian blue-cobalt oxide double layer for efficient all-inorganic multicolor electrochromic device. ACS Applied Electronic Materials, 2020, 2(6): 1768–1773

27 Kim D S, Park H, Hong S Y. . Low power stretchable active-matrix red, green, blue (RGB) electrochromic device array of poly(3-methylthiophene)/Prussian blue. Applied Surface Science, 2019, 471: 300–308

28 Fan M S, Kao S Y, Chang T H. . A high contrast solid-state electrochromic device based on nano-structural Prussian blue and poly(butyl viologen) thin films. Solar Energy Materials and Solar Cells, 2016, 145(1): 35–41

29 Huang B, Song J, Zhong J. . Prolonging lifespan of Prussian blue electrochromic films by an acid-free bulky-anion potassium organic electrolyte. Chemical Engineering Journal, 2022, 449: 137850

30 Kim S, Choi J. Photoelectrochemical anodization for the preparation of a thick tungsten oxide film. Electrochemistry Communications, 2012, 17: 10–13

31 Fang Y, Sun X, Cao H. Influence of PEG additive and annealing temperature on structural and electrochromic properties of sol-gel derived WO₃ films. Journal of Sol-Gel Science and Technology, 2011, 59(1): 145–152

32 Cheng K C, Chen F R, Kai J J. Electrochromic property of nano-composite Prussian blue based thin film. Electrochimica Acta, 2007, 52(9): 3330–3335

33 Chen Y, Bi Z, Li X. . High-coloration efficiency electrochromic device based on novel porous TiO₂@Prussian blue core-shell nanostructures. Electrochimica Acta, 2017, 224: 534–540

34 Xu H, Gong L, Zhou S. . Enhancing the electrochromic stability of Prussian blue based on TiO₂ nanorod arrays. New Journal of Chemistry, 2020, 44(6): 2236–2240

35 Xu M, Wang S, Zhou S. . Fast-switching speed and ultralong lifespan Au/Prussian blue electrochromic film for iris devices applications. Advanced Materials Interfaces, 2023, 10(7): 2201765

36 Kumar S S, Joseph J, Phani K L. Novel method for deposition of gold−Prussian blue nanocomposite films induced by electrochemically formed gold nanoparticles: Characterization and application to electrocatalysis. Chemistry of Materials, 2007, 19(19): 4722–4730

37 Wang Y, Gong Z, Zeng Y. . High-properties electrochromic device based on TiO₂@graphene/Prussian blue core-shell nanostructures. Chemical Engineering Journal, 2022, 431: 134066

38 Xu M, Wang S, Zhou S. . Construction of TiO₂@C@Prussian blue core-shell nanorod arrays for enhanced electrochromic switching speed and cycle stability. Journal of Alloys and Compounds, 2022, 908: 164410

39 Tang D, Wang J, Liu X A. . Low-spin Fe redox-based Prussian blue with excellent selective dual-band electrochromic modulation and energy-saving applications. Journal of Colloid and Interface Science, 2023, 636: 351–362

40 Nossol E, Zarbin A J G. A simple and innovative route to prepare a novel carbon nanotube/Prussian blue electrode and its utilization as a highly sensitive H₂O₂ amperometric sensor. Advanced Functional Materials, 2009, 19(24): 3980–3995

41 Ji X, Ren J, Ni R. . A stable and controllable Prussian blue layer electrodeposited on self-assembled monolayers for constructing highly sensitive glucose biosensor. Analyst, 2010, 135(8): 2092–2098

42 Chi Q, Dong S. Amperometric biosensors based on the immobilization of oxidases in a Prussian blue film by electrochemical codeposition. Analytica Chimica Acta, 1995, 310(3): 429–436

43 Ho K C, Chen C Y, Hsu H C. . Amperometric detection of morphine at a Prussian blue-modified indium tin oxide electrode. Biosensors & Bioelectronics, 2004, 20(1): 3–8

44 Zhai C, Sun X, Zhao W. . Acetylcholinesterase biosensor based on chitosan/Prussian blue/multiwall carbon nanotubes/hollow gold nanospheres nanocomposite film by one-step electrodeposition. Biosensors & Bioelectronics, 2013, 42: 124–130

45 Song Y, Zhang M, Wang L. . A novel biosensor based on acetylecholinesterase/Prussian blue-chitosan modified electrode for detection of carbaryl pesticides. Electrochimica Acta, 2011, 56(21): 7267–7271

46 Karyakin A A, Karyakina E E, Gorton L. Amperometric biosensor for glutamate using Prussian blue-based “artificial peroxidase” as a transducer for hydrogen peroxide. Analytical Chemistry, 2000, 72(7): 1720–1723

47 Isfahani V B, Memarian N, Dizaji H R. . The physical and electrochromic properties of Prussian blue thin films electrodeposited on ITO electrodes. Electrochimica Acta, 2019, 304: 282–291

48 Fu Z, Wei Y, Liu W. . Investigation of electrochromic device based on multi-step electrodeposited PB films. Ionics, 2021, 27(10): 4419–4427

49 Sekhavat M S, Ghodsi F E. Improving the electrochromic performance of Prussian blue (PB) thin films by using an innovative electrothermophoresis method. Journal of Materials Research, 2023, 38(10): 2852–2862

50 Lopes L C, Husmann S, Zarbin A J G. Chemically synthesized graphene as a precursor to Prussian blue-based nanocomposite: A multifunctional material for transparent aqueous K-ion battery or electrochromic device. Electrochimica Acta, 2020, 345: 136199

51 Ojha M, Pal M, Deepa M. Variable-tint electrochromic supercapacitor with a benzyl hexenyl viologen—Prussian blue architecture and ultralong cycling life. ACS Applied Electronic Materials, 2023, 5(4): 2401–2413

52 Pham N S, Nguyen L T, Nguyen H T. . A complementary electrochromic device based on Prussian blue and tungsten trioxide: The influence of switching time operation on high performance and long-term stability. Materials Letters, 2023, 343: 134356

53 Pham N S, Seo Y H, Park E. . Implementation of high-performance electrochromic device based on all-solution-fabricated Prussian blue and tungsten trioxide thin film. Electrochimica Acta, 2020, 353: 136446

54 Zhang W, Li H, Elezzabi A Y. A dual-mode electrochromic platform integrating zinc anode-based and rocking-chair electrochromic devices. Advanced Functional Materials, 2023, 33(24): 2300155

55 Ding Y, Wang M, Mei Z. . Flexible inorganic all-solid-state electrochromic devices toward visual energy storage and two-dimensional color tunability. ACS Applied Materials & Interfaces, 2023, 15(12): 15646–15656

56 Su Y, Wang Y, Lu Z. . A dual-function device with high coloring efficiency based on a highly stable electrochromic nanocomposite material. Chemical Engineering Journal, 2023, 456: 141075

57 Ma Q, Chen J, Zhang H. . Dual-function self-powered electrochromic batteries with energy storage and display enabled by potential difference. ACS Energy Letters, 2023, 8(1): 306–313

58 Chu J, Li X, Cheng Y. . Electrochromic properties of Prussian blue nanocube film directly grown on FTO substrates by hydrothermal method. Materials Letters, 2020, 258: 126782

59 Qian J, Ma D, Xu Z. . Electrochromic properties of hydrothermally grown Prussian blue film and device. Solar Energy Materials and Solar Cells, 2018, 177: 9–14

60 Yang Y, Peng Y, Jian Z. . Novel high-performance and low-cost electrochromic Prussian white film. ACS Applied Materials & Interfaces, 2022, 14(6): 8157–8162

61 Hong S F, Chen L C. Nano-Prussian blue analogue/PEDOT: PSS composites for electrochromic windows. Solar Energy Materials and Solar Cells, 2012, 104: 64–74

62 Shiozaki H, Kawamoto T, Tanaka H. . Electrochromic thin film fabricated using a water-dispersible ink of Prussian blue nanoparticles. Japanese Journal of Applied Physics, 2008, 47(2): 1242–1244

63 Jeong C Y, Kubota T, Tajima K. . Complementary electrochromic devices based on acrylic substrates for smart window applications in aircrafts. Materials Chemistry and Physics, 2022, 277: 125460

64 Tajima K, Watanabe H, Nishino M. . Green fabrication of a complementary electrochromic device using water-based ink containing nanoparticles of WO₃ and Prussian blue. RSC Advances, 2020, 10(5): 2562–2565

65 Jeong C Y, Kubota T, Tajima K. Flexible electrochromic devices based on tungsten oxide and Prussian blue nanoparticles for automobile applications. RSC Advances, 2021, 11(46): 28614–28620

66 Shen X, Wu S, Liu Y. . Morphology syntheses and properties of well-defined Prussian blue nanocrystals by a facile solution approach. Journal of Colloid and Interface Science, 2009, 329(1): 188–195

67 Ming H, Torad N L K, Chiang Y D. . Size- and shape-controlled synthesis of Prussian blue nanoparticles by a polyvinylpyrrolidone-assisted crystallization process. CrystEngComm, 2012, 14(10): 3387–3396

68 Ishizaki M, Kanaizuka K, Abe M. . Preparation of electrochromic Prussian blue nanoparticles dispersible into various solvents for realisation of printed electronics. Green Chemistry, 2012, 14(5): 1537–1544

69 Wang J Y, Wang M C, Jan D J. Synthesis of poly(methyl methacrylate)-succinonitrile composite polymer electrolyte and its application for flexible electrochromic devices. Solar Energy Materials and Solar Cells, 2017, 160: 476–483

70 Liao T C, Chen W H, Liao H Y. . Multicolor electrochromic thin films and devices based on the Prussian blue family nanoparticles. Solar Energy Materials and Solar Cells, 2016, 145(1): 26–34

71 Ding Y, Sun H, Li Z. . Galvanic-driven deposition of large-area Prussian blue films for flexible battery-type electrochromic devices. Journal of Materials Chemistry. A, Materials for Energy and Sustainability, 2023, 11(6): 2868–2875

72 Demiri S, Najdoski M, Velevska J. A simple chemical method for deposition of electrochromic Prussian blue thin films. Materials Research Bulletin, 2011, 46(12): 2484–2488

73 Elshorbagy M H, Ramadan R, Abdelhady K. Preparation and characterization of spray-deposited efficient Prussian blue electrochromic thin film. Optik, 2017, 129: 130–139

74 Kim J H, Park S, Ahn J. . Meniscus-guided micro-printing of Prussian blue for smart electrochromic display. Advanced Science, 2023, 10(3): 2205588

75 Wojdeł J C. First principles calculations on the influence of water-filled cavities on the electronic structure of Prussian blue. Journal of Molecular Modeling, 2009, 15(6): 567–572

76 Liu X, Zhou A, Dou Y. . Ultrafast switching of an electrochromic device based on layered double hydroxide/Prussian blue multilayered films. Nanoscale, 2015, 7(40): 17088–17095

77 Cong S, Tian Y, Li Q. . Single-crystalline tungsten oxide quantum dots for fast pseudocapacitor and electrochromic applications. Advanced Materials, 2014, 26(25): 4260–4267

78 Ko J H, Yeo S, Park J H. . Graphene-based electrochromic systems: The case of Prussian blue nanoparticles on transparent graphene film. Chemical Communications, 2012, 48(32): 3884–3886

79 Nossol E, Zarbin A J G. Electrochromic properties of carbon nanotubes/Prussian blue nanocomposite films. Solar Energy Materials and Solar Cells, 2013, 109: 40–46

80 Talagaeva N V, Zolotukhina E V, Bezverkhyy I. . Stability of Prussian blue–polypyrrole (PB/PPy) composite films synthesized via one-step redox-reaction procedure. Journal of Solid State Electrochemistry, 2015, 19(9): 2701–2709

81 DeLongchamp D M, Hammond P T. Multiple-color electrochromism from layer-by-layer-assembled polyaniline/Prussian blue nanocomposite thin films. Chemistry of Materials, 2004, 16(23): 4799–4805

82 Liu Z, Yang J, Leftheriotis G. . A solar-powered multifunctional and multimode electrochromic smart window based on WO₃/Prussian blue complementary structure. Sustainable Materials and Technologies, 2022, 31: e00372

83 Cai H, Chen Z, Guo S. . Polyacrylamide gel electrolyte for high-performance quasi-solid-state electrochromic devices. Solar Energy Materials and Solar Cells, 2023, 256: 112310

84 Xu G, Han Y, Li X. . A hydrogel electrolyte based on hydroxypropyl methylcellulose modified polyacrylamine for efficient electrochromic energy storage devices. European Polymer Journal, 2023, 186: 111856

85 Yue Y, Li H, Li K. . High-performance complementary electrochromic device based on WO₃·0.33H₂O/PEDOT and Prussian blue electrodes. Journal of Physics and Chemistry of Solids, 2017, 110: 284–289

86 Sun B, Liu Z, Li W. . A high-performance electrochromic battery based on complementary Prussian white/Li₄Ti₅O₁₂ thin film electrodes. Solar Energy Materials and Solar Cells, 2021, 231: 111314

87 Chen K C, Hsu C Y, Hu C W. . A complementary electrochromic device based on Prussian blue and poly(ProDOT-Et₂) with high contrast and high coloration efficiency. Solar Energy Materials and Solar Cells, 2011, 95(8): 2238–2245

88 Chaudhary A, Pathak D K, Tanwar M. . Prussian blue-viologen inorganic–organic hybrid blend for improved electrochromic performance. ACS Applied Electronic Materials, 2019, 1(6): 892–899

89 Bi Z, Li X, Chen Y. . Large-scale multifunctional electrochromic-energy storage device based on tungsten trioxide monohydrate nanosheets and Prussian white. ACS Applied Materials & Interfaces, 2017, 9(35): 29872–29880

90 Assis L M N, Sabadini R C, Santos L P. . Electrochromic device with Prussian blue and HPC-based electrolyte. Electrochimica Acta, 2015, 182: 878–883

91 Lu H C, Kao S Y, Chang T H. . An electrochromic device based on Prussian blue, self-immobilized vinyl benzyl viologen, and ferrocene. Solar Energy Materials and Solar Cells, 2016, 147: 75–84

92 Cai G, Cui M, Kumar V. . Ultra large optical modulation of electrochromic porous WO₃ film and the local monitoring of redox activity. Chemical Science, 2016, 7(2): 1373–1382

93 Weng D, Li M, Zheng J. . High-performance complementary electrochromic device based on surface-confined tungsten oxide and solution-phase N-methyl-phenothiazine with full spectrum absorption. Journal of Materials Science, 2017, 52(1): 86–95

94 Lin C F, Hsu C Y, Lo H C. . A complementary electrochromic system based on a Prussian blue thin film and a heptyl viologen solution. Solar Energy Materials and Solar Cells, 2011, 95(11): 3074–3080

95 Chen K C, Hsu C Y, Hu C W. . A complementary electrochromic device based on Prussian blue and poly(ProDOT-Et₂) with high contrast and high coloration efficiency. Solar Energy Materials and Solar Cells, 2011, 95(8): 2238–3080

96 Liu B J W, Zheng J, Wang J L. . Ultrathin W₁₈O₄₉ nanowire assemblies for electrochromic devices. Nano Letters, 2013, 13(8): 3589–3593

97 Jiao Z, Wang J, Ke L. . Electrochromic properties of nanostructured tungsten trioxide (hydrate) films and their applications in a complementary electrochromic device. Electrochimica Acta, 2012, 63: 153–160

98 Ahmadian-Alam L, Jahangiri F, Mahdavi H. Fabrication and assessment of an electrochromic and radar-absorbent dual device based on the new smart polythiophene-based/RGO/Fe₃O₄ ternary nanocomposite. Chemical Engineering Journal, 2021, 422: 130159

99 Wen R T, Granqvist C G, Niklasson G A. Eliminating degradation and uncovering ion-trapping dynamics in electrochromic WO₃ thin films. Nature Materials, 2015, 14(10): 996–1001

100 Mjejri I, Rougier A. Color switching in V₃O₇·H₂O films cycled in Li and Na based electrolytes: Novel vanadium oxide based electrochromic materials. Journal of Materials Chemistry. C, Materials for Optical and Electronic Devices, 2020, 8(11): 3631–3638

101 Wang Y, Wang S, Wang X. . A multicolour bistable electronic shelf label based on intramolecular proton-coupled electron transfer. Nature Materials, 2019, 18(12): 1335–1342

102 Zhang D, Wang J, Tong Z. . Bioinspired dynamically switchable PANI/PS-b-P2VP thin films for multicolored electrochromic displays with long-term durability. Advanced Functional Materials, 2021, 31(45): 2106577

103 Zhou K, Wang H, Jiu J. . Polyaniline films with modified nanostructure for bifunctional flexible multicolor electrochromic and supercapacitor applications. Chemical Engineering Journal, 2018, 345: 290–299

104 Ding Y, Wang M, Mei Z. . Novel Prussian white@MnO₂-based inorganic electrochromic energy storage devices with integrated flexibility, multicolor, and long life. ACS Applied Materials & Interfaces, 2022, 14(43): 48833–48843

105 Li H, Zhang W, Elezzabi A Y. Transparent zinc-mesh electrodes for solar-charging electrochromic windows. Advanced Materials, 2020, 32(43): 2003574

106 Li J, Yang P, Li X. . Ultrathin smart energy-storage devices for skin-interfaced wearable electronics. ACS Energy Letters, 2023, 8(1): 1–8

107 Kim Y, Han M, Kim J. . Electrochromic capacitive windows based on all conjugated polymers for a dual function smart window. Energy & Environmental Science, 2018, 11(8): 2124–2133

108 Li H, Elezzabi A Y. Simultaneously enabling dynamic transparency control and electrical energy storage via electrochromism. Nanoscale Horizons, 2020, 5(4): 691–695

109 Zhang H, Yu Y, Zhang L. . Self-powered fluorescence display devices based on a fast self-charging/recharging battery (Mg/Prussian blue). Chemical Science, 2016, 7(11): 6721–6727

110 Nanda O, Gupta N, Grover R. . Self-powered electrochromic window using green electrolyte. AIP Advances, 2018, 8(9): 095117

111 Wang J, Zhang L, Yu L. . A bi-functional device for self-powered electrochromic window and self-rechargeable transparent battery applications. Nature Communications, 2014, 5(1): 4921

112 Wang B, Cui M, Gao Y. . A long-life battery-type electrochromic window with remarkable energy storage ability. Solar RRL, 2020, 4(3): 1900425

113 Zhang H, Feng J, Sun F. . Self-driven Ni-based electrochromic devices for energy-efficient smart windows. Advanced Materials Technologies, 2023, 8(8): 2201688

114 Luo Y, Jin H, Lu Y. . Potential gradient-driven fast-switching electrochromic device. ACS Energy Letters, 2022, 7(6): 1880–1887

115 Zhao F, Zhao J, Zhang Y. . Self-powered quasi-solid-state electrochromic devices for optical information encryption. Journal of Materials Chemistry. C, Materials for Optical and Electronic Devices, 2021, 9(25): 7958–7966

116 Rathod P V, Puguan J M C, Kim H. Self-bleaching dual responsive poly(ionic liquid) with optical bistability toward climate-adaptable solar modulation. Chemical Engineering Journal, 2021, 422: 130065

117 Watanabe Y, Nagashima T, Nakamura K. . Continuous-tone images obtained using three primary-color electrochromic cells containing gel electrolyte. Solar Energy Materials and Solar Cells, 2012, 104: 140–145

118 Kobayashi N, Miura S, Nishimura M. . Organic electrochromism for a new color electronic paper. Solar Energy Materials and Solar Cells, 2008, 92(2): 136–139

119 Yu H, Shao S, Yan L. . Side-chain engineering of green color electrochromic polymer materials: Toward adaptive camouflage application. Journal of Materials Chemistry. C, Materials for Optical and Electronic Devices, 2016, 4(12): 2269–2273

120 Tajima K, Jeong C Y, Kubota T. . Mass-producible slit coating for large-area electrochromic devices. Solar Energy Materials and Solar Cells, 2021, 232: 111361

121 Macher S, Schott M, Dontigny M. . Large-area electrochromic devices on flexible polymer substrates with high optical contrast and enhanced cycling stability. Advanced Materials Technologies, 2021, 6(2): 2000836