Intrinsically stretchable polymer semiconductor film obtained via side-chain cross-linking for flexible polymer light-emitting diodes

Abstract

Stretchable polymer semiconductor film (SPSF) is the core to fabricate the flexible optoelectronic devices, due to its excellent strain-tolerance capacity. Softness of polymer chain realized via introducing flexible segment at the backbone and side-substituents is the effective strategy to obtain SPSFs, but easily causing the relatively instable film morphology and weak energy dissipation ability. Herein, we proposed a convenient side-chain cross-linked strategy to prepare the stretchable SPSF with an outstanding morphological stability for flexible polymer light-emitting diodes (PLED). Styrene group is introduced as ended cross-linking unit into the side chain of fluorene to prepare the intrinsically stretchable alter-copolymers semiconductors poly(9, 9-diphenyl-4-((6-(4-vinylphenoxy)hexyl)oxy)-9H-fluorene)-alt-(1,8-bis(4-phenoxy)octane) (PCm-alt-C8). Interestingly, PCm-alt-C8 cross-linked film easily obtained via thermal treatment at 180 °C, had stable morphology, excellent solvent resistance and deep-blue emission simultaneously. Compared to the controlled PEt-alt-C8, PCm-alt-C8 cross-linked films also present an excellent strain-tolerance capacity with larger crack initiation strain rates and the elongation at break (both enhanced by about 90%). More important, stretchable PCm-alt-C8 cross-linked films showed a stable electroluminescent and electrical property with large stretching degree (>30%) and hundreds of cycles of cycling stretch deformations, suggesting their excellent strain-tolerance capacity. Therefore, side-chain cross-linking is a universal strategy for the preparation of high-performance SPSF in flexible optoelectronics.

Keywords

stretchable polymer semiconductor films / side-chain cross-linking / thermal annealing processing / excellent stretching-deformation stability / flexible polymer light-emitting diode

References

[1] Zhong D-l, Wu C, Jiang Y-w, et al. . Highspeed and large-scale intrinsically stretchable integrated circuits [J]. Nature. 2024, 627(8003): 313-320

[2] Song T, Kong Q, Li S, et al. . Wearable flexible tactile triboelectric sensor Constructed with 3D printing for material perception [J]. Chemical Engineering Journal. 2025, 516: 163924

[3] Shim H, Sim K, Wang B-h, et al. . Elastic integrated electronics based on a stretchable n-type elastomer-semiconductor-elastomer stack [J]. Nature Electronics. 2023, 6(5): 349-359

[4] Zhao C-z, Park J, Root S E, et al. . Skin-inspired soft bioelectronic materials, devices and systems [J]. Nature Reviews Bioengineering. 2024, 2(8): 671-690

[5] Kwak W, Yin J-y, Wang S-l, et al. . Advances in triboelectric nanogenerators for self-powered wearable respiratory monitoring [J]. FlexMat. 2024, 1(1): 5-22

[6] Shi X, Zuo Y, Zhai P, et al. . Large-area display textiles integrated with functional systems [J]. Nature. 2021, 591(7849): 240-245

[7] Rogers J A, Someya T, Huang Y-G. Materials and mechanics for stretchable electronics [J]. Science. 2010, 327(5973): 1603-1607

[8] Liu N, Ma H-f, Li M-r, et al. . Electroconductive hydrogels for bioelectronics: Challenges and opportunities [J]. FlexMat. 2024, 1(3): 269-301

[9] Feng E-m, Zhang C-j, Han Y-f, et al. . Highspeed doctor-blading PM6: L8-BO organic solar cells from non-halogenated green solvent with a module efficiency of 16.07% [J]. Journal of Central South University. 2024, 31(12): 4297-4306

[10] Jin H, Matsuhisa N, Lee S, et al. . Enhancing the performance of stretchable conductors for E-textiles by controlled ink permeation [J]. Advanced Materials. 2017, 29(21): 1605848

[11] Guo X-h, Zhou X-l, Chu W-l, et al. . Remote vapor-phase dual alkali halide salts assisted quasi-van der Waals epitaxy of m-phase ZrO₂ thin films with high dielectric constant and stable flexible properties [J]. Applied Physics Letters. 2024, 125(8): 084101

[12] Wang Y, Zhu C-x, Pfattner R, et al. . A highly stretchable, transparent, and conductive polymer [J]. Science Advances. 2017, 3(3): e1602076

[13] Sun H-d, Du B-b, Wu Y-z, et al. . Interdiscipline between optoelectronic materials and mechanical sensors: Recent advances of organic triboluminescent compounds and their applications in sensing [J]. Journal of Central South University. 2021, 28(12): 3907-3934

[14] Wu J-h, Zhang S-w, Gu Q-f, et al. . Recent progress in covalent organic frameworks for flexible electronic devices [J]. FlexMat. 2024, 1(2): 160-172

[15] Ni M-j, An X, Bai L-b, et al. . Intrinsically stretchable and stable ultra-deep-blue fluorene-based polymer with a high emission efficiency of ≈90% for polymer light-emitting devices with a CIE_γ =0.06 [J]. Advanced Functional Materials. 2022, 32(5): 2106564

[16] Lu H-y, Yuan J-n, Chen Y-j, et al. . Super impact-resistant, high-strength, scratch-resistant, and foldable glass-like film for the next generation of ultra-thin flexible display [J]. FlexMat. 2025, 2(2): 132-144

[17] Yin D, Feng J, Ma R, et al. . Efficient and mechanically robust stretchable organic light-emitting devices by a laser-programmable buckling process [J]. Nature Communications. 2016, 7: 11573

[18] Sun H-d, Xiao Y-x, He Y-f, et al. . 3D printable organic room-temperature phosphorescent materials and printed real-time sensing and display devices [J]. Chemical Science. 2025, 16(12): 5299-5309

[19] Menard E, Meitl M A, Sun Y-g, et al. . Micro- and nanopatterning techniques for organic electronic and optoelectronic systems [J]. ChemInform. 2007, 38(31): 200731217

[20] Zhang Y-h, Fu H-r, Su Y-w, et al. . Mechanics of ultra-stretchable self-similar serpentine interconnects [J]. Acta Materialia. 2013, 61(20): 7816-7827

[21] Kim D H, Xiao J-l, Song J-z, et al. . Stretchable, curvilinear electronics based on inorganic materials [J]. Advanced Materials. 2010, 22(19): 2108-2124

[22] Zhang Z-t, Wang W-c, Jiang Y-w, et al. . High-brightness all-polymer stretchable LED with charge-trapping dilution [J]. Nature. 2022, 603(7902): 624-630

[23] Liu W, Zhang C, Alessandri R, et al. . High-efficiency stretchable light-emitting polymers from thermally activated delayed fluorescence [J]. Nature Materials. 2023, 22(6): 737-745

[24] Kim D C, Seung H, Yoo J, et al. . Intrinsically stretchable quantum dot light-emitting diodes [J]. Nature Electronics. 2024, 7(5): 365-374

[25] Zhu M-l, Shao Z-h, Li Y-f, et al. . Molecular-scale geometric design: Zigzag-structured intrinsically stretchable polymer semiconductors [J]. Journal of the American Chemical Society. 2024, 146(40): 27429-27442

[26] Shin M, Oh J Y, Byun K E, et al. . Polythiophene nanofibril bundles surface-embedded in elastomer: A route to a highly stretchable active channel layer [J]. Advanced Materials. 2015, 27(7): 1255-1261

[27] Song E, Kang B, Choi H H, et al. . Stretchable and transparent organic semiconducting thin film with conjugated polymer nanowires embedded in an elastomeric matrix [J]. Advanced Electronic Materials. 2016, 2(1): 1500250

[28] Peng Z-x, Xian K-h, Cui Y, et al. . Thermoplastic elastomer tunes phase structure and promotes stretchability of high-efficiency organic solar cells [J]. Advanced Materials. 2021, 33(49): 2106732

[29] Kang J, Mun J, Zheng Y, et al. . Tough-interface-enabled stretchable electronics using non-stretchable polymer semiconductors and conductors [J]. Nature Nanotechnology. 2022, 17(12): 1265-1271

[30] Zhang S, Alesadi A, Selivanova M, et al. . Toward the prediction and control of glass transition temperature for donor–acceptor polymers [J]. Advanced Functional Materials. 2020, 30(27): 2002221

[31] Zhang S, Alesadi A, Mason G T, et al. . Molecular origin of strain-induced chain alignment in PDPP-based semiconducting polymeric thin films [J]. Advanced Functional Materials. 2021, 31(21): 2100161

[32] Mun J, Ochiai Y, Wang W C, et al. . A design strategy for high mobility stretchable polymer semiconductors [J]. Nature Communications. 2021, 12: 3572

[33] Liu D Y, Mun J, Chen G, et al. . A design strategy for intrinsically stretchable high-performance polymer semiconductors: Incorporating conjugated rigid fused-rings with bulky side groups [J]. Journal of the American Chemical Society. 2021, 143(30): 11679-11689

[34] Wang G N, Shaw L, Xu J, et al. . Inducing elasticity through oligo-siloxane crosslinks for intrinsically stretchable semiconducting polymers [J]. Advanced Functional Materials. 2016, 26(40): 7254-7262

[35] Jang W, Lee M, Kweon H, et al. . Tetrabranched photo-crosslinker enables micrometer-scale patterning of light-emitting super yellow for high-resolution OLEDs [J]. ACS Photonics. 2021, 8(8): 2519-2528

[36] Müller C, Goffri S, Breiby D W, et al. . Tough, semiconducting polyethylene-poly(3-hexylthiophene) diblock copolymers [J]. Advanced Functional Materials. 2007, 17(15): 2674-2679

[37] Zhao Y, Zhao X-k, Zang Y-p, et al. . Conjugation-break spacers in semiconducting polymers: Impact on polymer processability and charge transport properties [J]. Macromolecules. 2015, 48(7): 2048-2053

[38] Schroeder B C, Chiu Y C, Gu X-d, et al. . Non-conjugated flexible linkers in semiconducting polymers: A pathway to improved processability without compromising device performance [J]. Advanced Electronic Materials. 2016, 2(7): 1600104

[39] Oh J Y, Rondeau-Gagné S, Chiu Y C, et al. . Intrinsically stretchable and healable semiconducting polymer for organic transistors [J]. Nature. 2016, 539(7629): 411-415

[40] Brovelli S, Sforazzini G, Serri M, et al. . Emission color trajectory and white electroluminescence through supramolecular control of energy transfer and exciplex formation in binary blends of conjugated polyrotaxanes [J]. Advanced Functional Materials. 2012, 22(20): 4284-4291

[41] Li J-w, Zheng Z-r, Ma Y-n, et al. . Mechanically ultra-robust fluorescent elastomer for elaborating auxetic composite [J]. Small. 2024, 20(36): e2402130

[42] Chen Y, Fan Z-w, Liu Y, et al. . Highly stretchable and tough elastomers from cyclic polymers [J]. Giant. 2023, 15: 100177

[43] Xiao Y-x, Li J-h, Song Z-h, et al. . 3D printable materials with visible light triggered photochromism and room temperature phosphorescence [J]. Journal of the American Chemical Society. 2025, 147(24): 20372-20380

[44] Davis A R, Carter K R. Controlling optoelectronic behavior in poly(fluorene) networks using thiol-ene photo-click chemistry [J]. Macromolecules. 2015, 48(6): 1711-1722

[45] Hunt A R, Stewart S K, Whiting A. Heck versus suzuki palladium catalysed cross-coupling of a vinylboronate ester with aryl halides [J]. Tetrahedron Letters. 1993, 34(22): 3599-3602

[46] Ni M-j, Zhuo Z-q, Zheng Y-y, et al. . High-efficiency intrinsically thermoplastic semiconducting polymer with excellent strain-tolerance capacity for flexible ultra-deep-blue polymer light-emitting diodes [J]. Advanced Materials. 2025, 37(8): e2411547

[47] Bai L-b, Han Y-m, Sun C, et al. . Unveiling the effects of interchain hydrogen bonds on solution gelation and mechanical properties of diarylfluorene-based semiconductor polymers [J]. Research. 2020, 2020: 3405826

[48] Zhuo Z-q, Ni M-j, An X, et al. . Intrinsically stretchable and efficient fully Π-conjugated polymer via internal plasticization for flexible deep-blue polymer light-emitting diodes with CIEy=0.08 [J]. Advanced Materials. 2023, 35(40): 2303923

[49] Zhuo Z-q, Ni M-j, Yu N-n, et al. . Intrinsically stretchable fully π-conjugated polymer film via fluid conjugated molecular external-plasticizing for flexible light-emitting diodes [J]. Nature Communications. 2024, 15: 7990

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Central South University