Game-Changers for Flexible Perovskite Solar Cells and Modules: Elastomers and Cross-Linking Molecules

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Learn More CiteCitationCitation and abstractCitation and referencesMore citation options ShareShare onFacebookX (Twitter)WeChatLinkedInRedditEmailJump toExpandCollapse ViewpointJanuary 1, 2025Game-Changers for Flexible Perovskite Solar Cells and Modules: Elastomers and Cross-Linking MoleculesClick to copy article linkArticle link copied!Luigi Angelo Castriotta*Luigi Angelo CastriottaCHOSE (Centre for Hybrid and Organic Solar Energy), Department of Electronic Engineering, University of Rome Tor Vergata, Via del Politecnico 1, 00133 Rome, Italy*[email protected]More by Luigi Angelo Castriottahttps://orcid.org/0000-0003-2525-8852Francesca De RossiFrancesca De RossiCHOSE (Centre for Hybrid and Organic Solar Energy), Department of Electronic Engineering, University of Rome Tor Vergata, Via del Politecnico 1, 00133 Rome, ItalyMore by Francesca De Rossihttps://orcid.org/0000-0002-6591-5928Matteo BonomoMatteo BonomoDepartment of Chemistry, NIS Interdepartmental Center and INSTM Reference Centre, University of Torino, Via Gioacchino Quarello 15/a, 10135 Torino, ItalyDepartment of Basic and Applied Sciences for Engineering (SBAI), Sapienza University of Rome, via Castro Laurenziano, 7, 00161 Rome, ItalyMore by Matteo Bonomohttps://orcid.org/0000-0002-1944-2664Open PDFACS Energy LettersCite this: ACS Energy Lett. 2025, 10, XXX, 283–286Click to copy citationCitation copied!https://pubs.acs.org/doi/10.1021/acsenergylett.4c02943https://doi.org/10.1021/acsenergylett.4c02943Published January 1, 2025 Publication History Received 24 October 2024Accepted 1 November 2024Published online 1 January 2025article-commentary© 2024 American Chemical Society. This publication is available under these Terms of Use. Request reuse permissionsThis publication is licensed for personal use by The American Chemical Society. ACS Publications© 2024 American Chemical SocietySubjectswhat are subjectsArticle subjects are automatically applied from the ACS Subject Taxonomy and describe the scientific concepts and themes of the article.ElastomersFlexibilityLayersNucleic acid structurePerovskitesPerovskite solar cells (PSCs) have garnered significant attention due to their high power conversion efficiency (PCE) and low production costs. (1) The perovskite materials used in these cells, typically composed of hybrid organic–inorganic lead halides, exhibit excellent light absorption and charge-carrier mobility and long diffusion lengths, all of which contribute to their superior photovoltaic performance among emerging photovoltaics (e.g., OPV, DSSC, etc.). (2) In addition to their high efficiency, now reaching up to 26.7% PCE on rigid substrates (3) and up to 25.1% on flexible substrates, (4,5) perovskites offer a unique advantage: they can be processed from solutions, which means they can be deposited onto a variety of substrates, including flexible ones. (6) However, these materials are inherently brittle and sensitive to residual tensile strains, which affect both the efficiency and the stability of the devices. The introduction of flexible substrates into PSCs (f-PSCs) has, on one side, provided an attractive pathway for the technology toward highly efficient, lightweight, shape-adaptable, and versatile solar energy solutions, suitable for application in wearable electronics, portable power sources, and building-integrated photovoltaics. (7) On the other side, it has also exacerbated the issues of brittleness and residual strain of the perovskite active layer, potentially limiting operation under mechanical stress, a common occurrence in flexible applications, and thus significantly hindering the widespread adoption of f-PSCs. (8) Flexible substrates, such as polyethyleneterephthalate (PET) and polyethylenenaphthalate (PEN), provide the necessary mechanical flexibility but also demand the active layers and interfaces within the solar cell to withstand repeated bending and stretching without significant performance degradation. (9) Strain engineering can play a vital role in addressing these challenges by incorporating elastomers and cross-linking molecules, according to several recent advancements reported in the literature (Figure 1). (10−13) In the past 10 years, the number of publications on elastomers or cross-linkers applied to PSCs has followed very closely the exponential trend in the number of publications on PSCs (regardless of the substrate), growing from less than 10 papers published in 2015 to over 200 in 2024, according to Scopus. Oddly, the same trend has not been observed for papers on elastomers or cross-linkers applied to f-PSCs, which can mainly benefit from employing such materials: the number of publications per year on this topic has fluctuated between 1 and 9. Undoubtedly, the publications on f-PSCs, even if increasing in number through the years, have been just a small fraction of those on all PSCs, i.e., around 2–3% depending on the year. Still, while the share of published papers on elastomers or cross-linkers for PSCs (regardless of the substrate) over the total publications on PSCs has been quite constantly in the 4–8% range, until reaching an 11% peak in 2024, the ratio of published papers on elastomers or cross-linkers for f-PSCs has always been higher, oscillating over the years between 13% and 23% of the total publications on f-PSCs, with 2024 marking the maximum so far, at 26%.Figure 1Figure 1. Illustration of elastomers and cross-linking molecules used in flexible perovskite solar cells (f-PSCs) for strain engineering. The various cross-linkers and elastomers, such as BTME, SBMA, TA-NI, PETA, and DSSP-PPU, contribute to improving the mechanical and thermal stability by mitigating the effects of compressive and tensile strain. These materials help distribute mechanical deformation across the perovskite films, enhancing the durability and performance of f-PSCs under mechanical stress.High Resolution ImageDownload MS PowerPoint SlideThis Viewpoint explores how elastomers and cross-linking molecules independently and synergistically offer exceptional flexibility, improve structural integrity and mechanical stability, provide self-healing capabilities, and boost the overall performance and stability of f-PSCs, ultimately driving the development of more durable, efficient, and commercially viable flexible photovoltaic technologies. It also investigates the existing gap in transferring the research advancements of these materials applied to PSCs from rigid to flexible substrates. Elastomers and Cross-Linking Molecules: What's the Difference?Elastomers and cross-linking molecules, though the terms are often used in conjunction, are distinct components with unique roles in enhancing the properties of f-PSCs. Elastomers are polymers known for their high elasticity and ability to undergo significant deformation before returning to their original shape, without any significant change in their pristine properties. They are critical in providing flexibility and self-healing properties to perovskite films. (14) Cross-linking molecules, on the other hand, are chemical agents that create covalent bonds between linear polymer chains, forming a network structure within the elastomer leading to a thermosetting material. (15) This cross-linking process significantly enhances the mechanical stability of the elastomer by preventing the polymer chains from sliding past each other easily, thereby distributing stress more evenly across the material. (16) While elastomers provide the foundational flexibility and resilience, cross-linking molecules improve structural integrity and durability, making the combined use of these materials essential for the robust performance of f-PSCs. In this context, the thoughtful design and combination of elastomers and cross-linking molecules is of paramount importance toward the production of PSC-tailored materials fully compatible with the active layer. Elastomers for f-PSCsElastomers are a class of polymers known for their exceptional elasticity and resilience. When integrated into the perovskite active layer, they serve multiple functions that address the key challenges of mechanical instability and material brittleness. Elastomers can be incorporated within the bulk of the perovskite absorber, at its grain boundaries, or in the encapsulation layers. Their flexibility allows the perovskite films to endure mechanical deformations, while their self-healing properties enable the repair of microcracks and other defects that may form under stress, thus avoiding the irreversible degradation of the active layer. When a f-PSC is subjected to bending, the externally applied stresses concentrate on the functional layers (such as SnO2 or perovskite) as well as at their interfaces, inducing interfacial stress due to the inherent mismatch between the Young's modulus of the adjacent layers. Once the applied stress exceeds the elastic deformation tolerance limit, structural failure occurs in the optoelectronic devices, resulting in performance degradation. Previous studies usually attributed the mechanical degradation of flexible PSCs to crack formation in the bulk of the perovskite film or delamination at the charge transport layer/perovskite interfaces. Therefore, tremendous efforts have been devoted to minimize the Young's modulus of bulk perovskite films and enhance their interfacial toughness. Elastomers with a low Young's modulus, such as polyurethane (17,18) and polysiloxane, (19,20) have been incorporated in bulk perovskites to strengthen the binding between neighboring grains. Buffer layers with multiple functional groups (e.g., −C═O, −OH, −Si–O, and −F) have been incorporated between perovskites and transport layers to increase their contact strengths through noncovalent intermolecular interactions. (21,22) Recent studies have demonstrated the effectiveness of various elastomers in enhancing the mechanical properties of perovskite films. For instance, supramolecular polyurethane elastomers have been shown to act as dynamic "ligaments" within the perovskite structure. (18,23) These elastomers release residual stress, soften the grain boundaries, and provide room-temperature self-healing capabilities. As a result, perovskite films incorporating these elastomers exhibit remarkable flexibility, retaining nearly 80% of their initial efficiency after 8,000 bending cycles with a bending radius of 2 mm. Furthermore, the self-healing process can recover almost 90% of the initial efficiency, significantly extending the operational lifespan of the f-PSCs. Another breakthrough involves the use of self-healing ionic conductive elastomers (ICEs) containing imidazolium-based ionic liquids (ILs). These ICEs can repair grain boundary cracks at room temperature, a crucial feature for the longevity and reliability of f-PSCs in real-world applications. Devices incorporating ICEs have achieved record PCEs of 24.84% and demonstrated the ability to recover 91% of their initial efficiency after 10,000 bending cycles with a bending radius of 5 mm at room temperature. (10) Cross-Linking Molecules for f-PSCsCross-linking molecules play a crucial role in improving the mechanical and thermal stability of f-PSCs. By forming covalent bonds between polymer chains, these molecules establish a network that enhances the material's toughness, effectively distributing stress throughout the material and preventing localized failure. This improves the overall mechanical properties of the perovskite films. For example, incorporating cross-linking agents like bis(trimethoxysilyl)ethane (BTME) or other silane-based agents has been shown to create robust and flexible networks within the perovskite structure, enhancing the film's ability to withstand mechanical stress and thermal fluctuations. (24,25) Recent studies have demonstrated the use of novel cross-linkers like 4,5-(3-methyloxetane) dicarboxylate imidazole (MZ), which coordinates with Pb2+ to form a mesoporous lead iodide scaffold. (26) This configuration regulates the crystallization kinetics, alleviating residual strain and enhancing spatial composition homogeneity in the perovskite films. Such advancements contribute to both the environmental and operational stability of f-PSCs by forming durable barriers that protect against moisture and oxygen, thereby extending the lifespan of the solar cells and mitigating the risk of leakage of toxic byproducts. The Quest for Tailored MaterialsAs proof of concept for the use of both elastomers and cross-linkers within the PSCs field, mainly commercially available and well-established materials have been tested so far, whereas only a few innovative approaches have been proposed, exploiting the synergy with other classes of materials (e.g., ILs). On the one hand, the large availability and full knowledge of conventional materials allow researchers to more specifically understand their effect in the stabilization of the perovskite active layer; on the other hand, this approach dramatically limits the almost endless tunability of these additives. As such, the next generation of both elastomers and cross-linking molecules (and even more their combination) calls for a joint effort among chemists, material scientists, and electronic engineers toward the thoughtful design of composite materials to be (i) fully compatible with the perovskite active layer, (ii) easily implemented into the device fabrication process, (iii) synthesized via cost-effective, clean, and sustainable routes, and (iv) easily separated from the device to facilitate their recovery and recycling in the end-of-life phase. Elastomers and cross-linking molecules play pivotal roles in the advancement of flexible perovskite solar cells, offering complementary solutions to the mechanical and environmental challenges that hinder their performance and durability. As research progresses, the integration of advanced and specifically designed elastomers and cross-linking agents is expected to drive further innovations, paving the way for the widespread adoption of flexible, efficient, and durable solar energy solutions.Author InformationClick to copy section linkSection link copied!Corresponding AuthorLuigi Angelo Castriotta - CHOSE (Centre for Hybrid and Organic Solar Energy), Department of Electronic Engineering, University of Rome Tor Vergata, Via del Politecnico 1, 00133 Rome, Italy; https://orcid.org/0000-0003-2525-8852; Email: [email protected]AuthorsFrancesca De Rossi - CHOSE (Centre for Hybrid and Organic Solar Energy), Department of Electronic Engineering, University of Rome Tor Vergata, Via del Politecnico 1, 00133 Rome, Italy; https://orcid.org/0000-0002-6591-5928Matteo Bonomo - Department of Chemistry, NIS Interdepartmental Center and INSTM Reference Centre, University of Torino, Via Gioacchino Quarello 15/a, 10135 Torino, Italy; Department of Basic and Applied Sciences for Engineering (SBAI), Sapienza University of Rome, via Castro Laurenziano, 7, 00161 Rome, Italy; https://orcid.org/0000-0002-1944-2664NotesViews expressed in this Viewpoint are those of the authors and not necessarily the views of the ACS.The authors declare no competing financial interest.AcknowledgmentsClick to copy section linkSection link copied!This project has received funding from the European Union's Framework Programme for Research and Innovation Horizon Europe (2021-2027) under the Marie Sklodowska-Curie Grant Agreement No. 101068387 EFESO. This research was funded by the Clean Energy Transition Partnership under the 2022 CET Partnership joint call for research proposal, cofunded by the European Commission (GA No. 101069750) and with the funding organizations detailed on https://cetpartnership.eu/funding-agencies-and-call-modules. This research acknowledges support from Project CH4.0 under the MUR program "Dipartimenti di Eccellenza 2023–2027" (CUP D13C22003520001).ReferencesClick to copy section linkSection link copied! This article references 26 other publications. 1Green, M. A.; Ho-Baillie, A.; Snaith, H. J. J. N. p. The emergence of perovskite solar cells. Nat. Photonics 2014, 8 (7), 506– 514, DOI: 10.1038/nphoton.2014.134 Google Scholar1The emergence of perovskite solar cellsGreen, Martin A.; Ho-Baillie, Anita; Snaith, Henry J.Nature Photonics (2014), 8 (7), 506-514CODEN: NPAHBY; ISSN:1749-4885. (Nature Publishing Group) A review. The past two years have seen the unprecedentedly rapid emergence of a new class of solar cell based on mixed org.-inorg. halide perovskites. Although the first efficient solid-state perovskite cells were reported only in mid-2012, extremely rapid progress was made during 2013 with energy conversion efficiencies reaching a confirmed 16.2% at the end of the year. This increased to a confirmed efficiency of 17.9% in early 2014, with unconfirmed values as high as 19.3% claimed. Moreover, a broad range of different fabrication approaches and device concepts is represented among the highest performing devices - this diversity suggests that performance is still far from fully optimized. This Review briefly outlines notable achievements to date, describes the unique attributes of these perovskites leading to their rapid emergence and discusses challenges facing the successful development and commercialization of perovskite solar cells. >> More from SciFinder ®https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXhtVGqu7zN&md5=35b95cd94a6e7b9242c6206367f2ba792Almora, O.; Cabrera, C. I.; Erten-Ela, S.; Forberich, K.; Fukuda, K.; Guo, F.; Hauch, J.; Ho-Baillie, A. W.; Jacobsson, T. J.; Janssen, R. A. J. A. e. m. Device Performance of Emerging Photovoltaic Materials (Version 4). Adv. Energy Mater. 2024, 14 (4), 2303173, DOI: 10.1002/aenm.202303173 Google ScholarThere is no corresponding record for this reference.3Green, M. A.; Dunlop, E. D.; Yoshita, M.; Kopidakis, N.; Bothe, K.; Siefer, G.; Hinken, D.; Rauer, M.; Hohl-Ebinger, J.; Hao, X. Solar cell efficiency tables (Version 64). Progress in Photovoltaics 2024, 32 (7), 425– 441, DOI: 10.1002/pip.3831 Google ScholarThere is no corresponding record for this reference.4Ren, N.; Tan, L.; Li, M.; Zhou, J.; Ye, Y.; Jiao, B.; Ding, L.; Yi, C. 25% - Efficiency flexible perovskite solar cells via controllable growth of SnO2. iEnergy 2024, 3 (1), 39– 45, DOI: 10.23919/IEN.2024.0001 Google ScholarThere is no corresponding record for this reference.5Tong, X.; Xie, L.; Li, J.; Pu, Z.; Du, S.; Yang, M.; Gao, Y.; He, M.; Wu, S.; Mai, Y.; Ge, Z. Large Orientation Angle Buried Substrate Enables Efficient Flexible Perovskite Solar Cells and Modules. Adv. Mater. 2024, 36 (38), 2407032, DOI: 10.1002/adma.202407032 Google ScholarThere is no corresponding record for this reference.6Wang, P.; Wu, Y.; Cai, B.; Ma, Q.; Zheng, X.; Zhang, W.-H. Solution-Processable Perovskite Solar Cells toward Commercialization: Progress and Challenges. Adv. Funct. Mater. 2019, 29 (47), 1807661, DOI: 10.1002/adfm.201807661 Google Scholar6Solution-Processable Perovskite Solar Cells toward Commercialization: Progress and ChallengesWang, Peng; Wu, Yihui; Cai, Bing; Ma, Qingshan; Zheng, Xiaojia; Zhang, Wen-HuaAdvanced Functional Materials (2019), 29 (47), 1807661CODEN: AFMDC6; ISSN:1616-301X. (Wiley-VCH Verlag GmbH & Co. KGaA) A review. In the last few years, organometal halide perovskites (OHPs) have emerged as a promising candidate for photovoltaic (PV) applications. A certified efficiency ≤23.7% was achieved, which is comparable with most of the well-established PV technologies. Their good soly. due to the ionic nature enables versatile low-temp. soln. processes, including blade coating, slot-die coating, etc., most of which are scalable and compatible with roll-to-roll large-scale manufg. processes. The low cost, high efficiency, and facile processable features make perovskite solar cells (PSCs) a very competitive PV technol. Despite the great progress, long-term durability concerns, toxicity issues of both materials and manufg. process, and lack of robust high-throughput prodn. technol. for fabricating efficient large-area modules are major obstacles toward commercialization. In this review, the recent progress of com. available process of PSCs is surveyed, the underlying determinants for up-scaling high-quality PSCs from hydrodynamic characteristics and crystn. thermodn. mechanism are identified, the influence of external stress factors on stability of PSCs and intrinsic instability mechanism in OHPs themselves is revealed, and the environmental impact and sustainable development of PSC technol. are analyzed. Strategies and opportunities for large-scale prodn. of PSCs probably promote the development of PSCs toward commercialization. >> More from SciFinder ®https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXmvVCmtbg%253D&md5=de07d597ffe4d5b27314ae30951b18c77Jung, H. S.; Han, G. S.; Park, N.-G.; Ko, M. J. J. J. Flexible perovskite solar cells. Joule 2019, 3 (8), 1850– 1880, DOI: 10.1016/j.joule.2019.07.023 Google Scholar7Flexible Perovskite Solar CellsJung, Hyun Suk; Han, Gill Sang; Park, Nam-Gyu; Ko, Min JaeJoule (2019), 3 (8), 1850-1880CODEN: JOULBR; ISSN:2542-4351. (Cell Press) A review. Since the first report on solid-state perovskite solar cells (PSCs) with 9.7% efficiency and 500-h long-term stability in 2012, PSCs have achieved an amazing power-conversion efficiency (PCE) of 24.2%, exceeding the PCEs of multi-cryst. Si (22.3%), thin-film cryst. Si (21.2%), copper indium gallium selenide (22.6%), and CdTe-based thin-film SCs (22.1%), and are suitable for transforming into flexible solar cells based on plastic substrates. The light wt. and flexibility of flexible-PSCs (F-PSCs) allows their use in niche applications such as portable elec. chargers, electronic textiles, large-scale industrial roofing, and power sources for unmanned aerial vehicles (UAVs). However, the F-PSCs always exhibit inferior efficiency compared to rigid PSCs, i.e., champion-cell efficiency of F-PSCs is 19.11%, which is apparently lower than that of rigid cells. Also, the world-best module efficiency for rigid perovskite module is 17.18% (30 cm2) higher than that for flexible perovskite module efficiency, 15.22% (30 cm2). Moreover, the F-PSCs have not shown better long-term stability in comparison with rigid PSCs. In this review paper, we investigate fundamental challenges of F-PSCs regarding relatively low efficiency and stability and demonstrate the recent efforts to overcome big hurdles. Also, current attempts for the commercialization of F-PSCs are introduced. >> More from SciFinder ®https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXhs1aru7jE&md5=07dd238f16bee2530fc1aaf95fd28b6f8Liang, H.; Yang, W.; Xia, J.; Gu, H.; Meng, X.; Yang, G.; Fu, Y.; Wang, B.; Cai, H.; Chen, Y.; Yang, S.; Liang, C. Strain Effects on Flexible Perovskite Solar Cells. Advanced Science 2023, 10 (35), 2304733, DOI: 10.1002/advs.202304733 Google ScholarThere is no corresponding record for this reference.9Tian, R.; Zhou, S.; Meng, Y.; Liu, C.; Ge, Z. J. A. M. Material and device design of flexible perovskite solar cells for next-generation power supplies. Adv. Mater. 2024, 36, 2311473, DOI: 10.1002/adma.202311473 Google ScholarThere is no corresponding record for this reference.10Xue, T.; Fan, B.; Jiang, K.-J.; Guo, Q.; Hu, X.; Su, M.; Zhou, E.; Song, Y. Self-healing ion-conducting elastomer towards record efficient flexible perovskite solar cells with excellent recoverable mechanical stability. Energy Environ. Sci. 2024, 17 (7), 2621– 2630, DOI: 10.1039/D4EE00462K Google ScholarThere is no corresponding record for this reference.11Wang, Y.; Meng, Y.; Liu, C.; Cao, R.; Han, B.; Xie, L.; Tian, R.; Lu, X.; Song, Z.; Li, J. J. J. Utilizing electrostatic dynamic bonds in zwitterion elastomer for self-curing of flexible perovskite solar cells. Joule 2024, 8 (4), 1120– 1141, DOI: 10.1016/j.joule.2024.01.021 Google ScholarThere is no corresponding record for this reference.12Tu, S.; Gang, Y.; Lin, Y.; Liu, X.; Zhong, Y.; Yu, D.; Li, X. J. S. Triple Cross-Linking Engineering Strategies for Efficient and Stable Inverted Flexible Perovskite Solar Cells. Small 2024, 20, 2310868, DOI: 10.1002/smll.202310868 Google ScholarThere is no corresponding record for this reference.13Wang, Y.; Cao, R.; Meng, Y.; Han, B.; Tian, R.; Lu, X.; Song, Z.; Yang, S.; Lu, C.; Liu, C.; Ge, Z. Mechanical robust and self-healing flexible perovskite solar cells with efficiency exceeding 23%. Science China Chemistry 2024, 67 (8), 2670– 2678, DOI: 10.1007/s11426-024-1954-8 Google ScholarThere is no corresponding record for this reference.14Bhowmick, A. K.; Stephens, H. Handbook of elastomers; CRC Press, 2000.Google ScholarThere is no corresponding record for this reference.15Nielsen, L. E. Cross-linking-effect on physical properties of polymers. J. Macromol. Sci. C 1969, 3 (1), 69– 103, DOI: 10.1080/15583726908545897 Google ScholarThere is no corresponding record for this reference.16Maitra, J.; Shukla, V. K. Cross-linking in hydrogels-a review. Am. J. Polym. Sci. 2014, 4 (2), 25– 31, DOI: 10.5923/j.ajps.20140402.01 Google Scholar16Cross-linking in hydrogels - a reviewMaitra, Jaya; Shukla, Vivek KumarAmerican Journal of Polymer Science (2014), 4 (2), 25-31, 7 pp.CODEN: AJPSM2; ISSN:2163-1344. (Scientific & Academic Publishing Co.) Hydrogels represent a class of high water content polymers with phys. or chem. crosslinks. Their phys. properties are similar to soft tissues. Cross linking is a stabilization process in polymer chem. which leads to multidimensional extension of polymeric chain resulting in network structure. Cross-link is a bond which links one polymer chain to other. It can be ionic or covalent. Cross linking changes a liq. polymer into 'solid' or 'gel' by restricting the ability of movement. When polymer chains are linked together by cross-links, they lose some of their ability to move as individual polymer chains. A liq. polymer (where the chains are freely flowing) can be turned into a 'solid' or 'gel' by crosslinking the chains together. Cross linking increases the mol. mass of a polymer. Cross-linked polymers are important because they are mech. strong and resistant to heat, wear and attack by solvents. However, the drawback assocd. with cross-linked polymers is that they are relatively inflexible when it comes to their processing properties because they are insol. and infusible. >> More from SciFinder ®https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXhtlCnt7rI&md5=a860fbd7caac792404e49742b32aa7c617Huang, Z.; Hu, X.; Liu, C.; Tan, L.; Chen, Y. J. A. F. M. Nucleation and crystallization control via polyurethane to enhance the bendability of perovskite solar cells with excellent device performance. Adv. Funct. Mater. 2017, 27 (41), 1703061, DOI: 10.1002/adfm.201703061 Google ScholarThere is no corresponding record for this reference.18Yang, Z.; Jiang, Y.; Wang, Y.; Li, G.; You, Q.; Wang, Z.; Gao, X.; Lu, X.; Shi, X.; Zhou, G. J. S. Supramolecular Polyurethane "Ligaments" Enabling Room-Temperature Self-Healing Flexible Perovskite Solar Cells and Mini-Modules. Small 2024, 20 (9), 2307186, DOI: 10.1002/smll.202307186 Google ScholarThere is no corresponding record for this reference.19Jiang, F.; Thangavel, G.; Lee, J. P.; Gupta, A.; Zhang, Y.; Yu, J.; Yokota, T.; Yamagishi, K.; Zhang, Y.; Someya, T.; Lee, P. S. Self-healable and stretchable perovskite-elastomer gas-solid triboelectric nanogenerator for gesture recognition and gripper sensing. Science Advances 2024, 10 (41), eadq5778 DOI: 10.1126/sciadv.adq5778 Google ScholarThere is no corresponding record for this reference.20Wu, Y.; Xu, G.; Shen, Y.; Wu, X.; Tang, X.; Han, C.; Chen, Y.; Yang, F.; Chen, H.; Li, Y.; Li, Y. Stereoscopic Polymer Network for Developing Mechanically Robust Flexible Perovskite Solar Cells with an Efficiency Approaching 25%. Adv. Mater. 2024, 36, 2403531, DOI: 10.1002/adma.202403531 Google ScholarThere is no corresponding record for this reference.21Qiu, L.; Si, G.; Bao, X.; Liu, J.; Guan, M.; Wu, Y.; Qi, X.; Xing, G.; Dai, Z.; Bao, Q.; Li, G. Interfacial engineering of halide perovskites and two-dimensional materials. Chem. Soc. Rev. 2023, 52 (1), 212– 247, DOI: 10.1039/D2CS00218C Google ScholarThere is no corresponding record for this reference.22Zhou, Y.; Li, L.; Han, Z.; Li, Q.; He, J.; Wang, Q. J. C. R. Self-healing polymers for electronics and energy devices. Chem. Rev. 2023, 123 (2), 558– 612, DOI: 10.1021/acs.chemrev.2c00231 Google Scholar22Self-healing polymers for electronics and energy devicesZhou, Yao; Li, Li; Han, Zhubing; Li, Qi; He, Jinliang; Wang, QingChemical Reviews (Washington, DC, United States) (2023), 123 (2),