Enabling efficient electron injection in stretchable OLED

Nature Materials (2025)Cite this article Stretchable organic light-emitting diodes (OLEDs) are transforming human–machine interfaces and wearable technologies; still, their performance is considerably inferior to commercial, non-stretchable OLEDs, mainly limited by inefficient electron injection. We address this by redesigning both the electron transport layer and the cathode. For the former, we design a copolymer structure with high stretchability and ideal energy levels, achieving performance comparable with standard small-molecule electron transport layers. For the latter, we leverage the liquid metals embrittlement effect to confer stretchability to aluminium thin films, without compromising their electrical and optical characteristics. Combining these designs, we demonstrate fully stretchable OLEDs with a very high external quantum efficiency of 8% and a very low turn-on voltage of 3.5 V, which is on par with the reference rigid OLEDs utilizing the same emitter. This work tackles a crucial bottleneck in stretchable OLED development, bridging the performance gap between stretchable OLEDs and standard rigid OLEDs at the device level, paving the way for high-performance, skin-like displays.This is a preview of subscription content, access via your institution Access Nature and 54 other Nature Portfolio journals Get Nature+, our best-value online-access subscription $32.99 / 30 days cancel any timeSubscribe to this journal Receive 12 print issues and online access $259.00 per yearonly $21.58 per issueBuy this articleUSD 39.95Prices may be subject to local taxes which are calculated during checkoutThe data that support the findings of this study are available within this Article and its Supplementary Information. Additional data are available from the corresponding authors upon request. 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Mater. 26, 4253–4259 (2014).Article CAS PubMed Google Scholar Download referencesThis research is supported by the National Science Foundation (NSF) CAREER award number 2239618, and partially supported by the US National Institutes of Health (1DP2EB034563). This work, performed at the Center for Nanoscale Materials, a US Department of Energy (DOE) Office of Science User Facility, was supported by the US DOE, Office of Basic Energy Sciences, under contract no. DE-AC02-06CH11357. This work made use of the focused-ion-beam SEM core facility (RRID: SCR_025212) in the Department of Geophysical Sciences at the University of Chicago. J.J.d.P. acknowledges support from MICCoM, as part of the Computational Materials Sciences Program funded by the US Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division, under grant number DOE/BES 5J-30161-0010A. P.G. acknowledges support from the US Air Force Office of Scientific Research (grant number FA9550-22-1-0209). We thank H. Wang and W. Lee for discussion of the new liquid metal AlGaIn. S. Wang is a CZ Biohub Investigator.Wei LiuPresent address: Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University, Suzhou, ChinaThese authors contributed equally: Wei Liu, Cheng Zhang, Zhiming Zhang.Pritzker School of Molecular Engineering, The University of Chicago, Chicago, IL, USAWei Liu, Cheng Zhang, Zhiming Zhang, Yang Li, Shinya Wai, Yahao Dai, Glingna Wang, Naisong Shan, Songsong Li, Jie Xu, Juan J. de Pablo & Sihong WangNanoscience and Technology Division, Argonne National Laboratory, Lemont, IL, USAAikaterini Vriza, Benjamin T. Diroll, Jie Xu & Sihong WangAdvanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, USAYunfei Wang & Chenhui ZhuDepartment of Chemical and Environmental Engineering, Yale University, New Haven, CT, USADu Chen & Peijun GuoEnergy Sciences Institute, Yale University, West Haven, CT, USADu Chen & Peijun GuoCenter for Molecular Engineering, Argonne National Laboratory, Lemont, IL, USAJuan J. de Pablo & Sihong WangCZ Biohub Chicago LLC, Chicago, IL, USASihong WangSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarW.L. and S. Wang conceived the research. W.L. designed and carried out the experiments. Z.Z., Y.L., Y.D., G.W., N.S. and S.L. helped with the device fabrications and material characterizations. A.V. performed the DFT calculations. C. Zhang performed the MD simulation. S. Wai performed the SEM and EDS measurements. Y.W. and C. Zhu performed the GIWAXS characterizations. B.T.D. performed the photoluminescence transient decay measurements. D.C. and P.G. helped with the low-temperature phosphorescence measurement. S. Wang and J.J.d.P. supervised the research. W.L. and S. Wang wrote the manuscript. All authors contributed to the discussion and manuscript revision.Correspondence to Juan J. de Pablo or Sihong Wang.S. Wang, J.J.d.P., W.L. and C. Zhang are inventors on a pending patent filed by the University of Chicago (number UCHI 25-T-179). The remaining authors declare no competing interests.Nature Materials thanks Jin Young Oh, Benjamin Tee and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.a, The molecular structure of the stretchable ETL polymers. The conjugated tri-repeating unit is in the blue dashed frame, while the non-conjugated repeating unit is in the red dashed frame. b, The optimized structure, HOMO, and LUMO distributions for the conjugated tri-repeating unit of the stretchable ETL polymers. c, The optimized structure, HOMO, and LUMO distributions for the non-conjugated repeating unit of the stretchable ETL polymers.a-f, 2D GIWAXS patterns of the ETL-polymer films on 3-(trimethoxysilyl)propyl methacrylate (MPTS)-treated Si-substrates (Si-MPTS), and the substrate (Si-MPTS) alone. g-j, 1D linecuts in the out-of-plane direction and the in-plane direction of the ETL-polymer films on Si-MPTS substrates, and bare substrate (Si-MPTS) alone. The MPTS treatment on Si substrates was to facilitate film depositions.Source dataa, Representative current density-voltage traces for electron-only devices based on the ETL polymers with the device structure of Al (80 nm)/ETL polymers/LiF (1 nm)/Al (80 nm). The film thicknesses of the ETL polymers are 80.4 nm, 95.5 nm, 91.1 nm, 84.5 nm, and 97.5 nm, respectively, for PTG, PTG25D, PTG50D, PTG75D, and PTGD. b, Representative electron mobilities of ETL polymers plotted as a function of the square root of the electric field. The electron mobility (μ) of the polymers is calculated based on the space charge-limited current (SCLC) model by the equation: \(J=\frac{9{\varepsilon }_{{\rm{r}}}{\varepsilon }_{0}\mu {V}^{2}}{8{d}^{3}}\) where εr is the relative dielectric constant, ε0 is the permittivity of free space, d is the thickness of ETL-polymer film, and V is the effective applied voltage in the device.Source dataa, Chemical structures of polymers PFN-Br and PEIE, the schematic of the energy-level alignment of PFN-Br_PEIE with EML (PDKCH), as well as the reasons for the poor performance of OLED based on PFN-Br_PEIE, such as triplet-exciton quenching via non-radiative decay due to the low T1 of PFN-Br_PEIE, and hole current leaking due to the slightly shallow HOMO of PFN-Br_PEIE (Supplementary Table 1). b, Chemical structures of small-molecule ETL materials TPBI and TmPyPB, the schematic of energy-level alignment of stretchable ETL polymers, TPBI, and TmPyPB with EML (PDKCH). c, Representative current density-voltage traces for the hole-only devices based on our representative ETL polymer (that is, PTG25D) and PEIE_PFN-Br, revealing the better hole blocking ability of our ETL polymers in comparison with that of the PEIE_PFN-Br composite. The architectures for the hole-only devices are ITO/PEDOT:PSS_PFI/PDKCH/ETL (PTG25D or PEIE_PFN-Br)/MoO3/Al.Source dataOptical microscopy images of ETL-polymer thin films stretched to the strains of 25%, 50%, 75%, and 100%, as well as released from 100% strain.Sample preparation methodology used for characterizations of the embrittlement effect.a–c, Optical microscopy images of an embrittled Al film (a) an untreated Al film (b) and a film with an interface between the embrittled Al and the untreated Al released from 100% strain (c).a, Representative J-V traces for the electron-only devices with different cathodes. The device structure is Al/SY/EIL/cathode. SY or super yellow, poly(1,4-phenylenevinylene) (PPV). b, Photoemission cutoffs obtained via UPS for Al, AgNW, and PEDOT:PSS samples, with and without the EIL modification. The device structures are ITO/our new ETL polymer or SY/EIL/cathode. The work functions of different cathodes are estimated from the UPS testing. The AgNW electrode is the same as the one we used as the anode for the fully stretchable OLED, the PEDOT:PSS electrode is based on a spin-coated film with a mix solution of PEDOT:PSS (PH 1000) with 6% of D-sorbitol.Source dataa, Chemical structures of the blue emitter PTrz-tBuCz and the red emitter MEH-PPV. b, J-V, c, L-V traces, d, CIE coordinates, and e, spectra, of blue and red stretchable OLEDs with device structures of AgNW/PEDOT:PSS_PFI/EML (red or blue)/LiF/embrittled Al/AlGaIn. The structures of the control OLEDs are AgNW/PEDOT:PSS_PFI/EML/PEIE_PFN-Br/AgNW. PTrz-tBuCz is adopted from our earlier work1, MEH-PPV is purchased from Sigma-Aldrich.Source dataSupplementary Figs. 1–37 and Tables 1 and 2.Original data.Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.Reprints and permissionsLiu, W., Zhang, C., Zhang, Z. et al. Enabling efficient electron injection in stretchable OLED. Nat. Mater. (2025). https://doi.org/10.1038/s41563-025-02419-zDownload citationReceived: 10 February 2025Accepted: 24 October 2025Published: 26 November 2025Version of record: 26 November 2025DOI: https://doi.org/10.1038/s41563-025-02419-zAnyone you share the following link with will be able to read this content:Sorry, a shareable link is not currently available for this article. 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