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Page 18 of 32 Keum et al. Soft Sci 2024;4:34 https://dx.doi.org/10.20517/ss.2024.26

Figure 10. Various emissive materials for stretchable displays. (A) Stretchable PLED emission layers fabricated by blending emitting
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polymer with elastomers . Copyright 2022, ACS Publications; (B) Stretchable luminescent ion-gel with dynamic coordination and
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hydrogen bond . Copyright 2023, ACS Publications; (C) Stretchable ACEL fabricated by blending high-permittivity elastomers and
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inorganic phosphors . Copyright 2024, Wiley-VCH; (D) Inorganic ZnS phosphor-based stretchable EL device integrating PEDOT:PSS-
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PAAm hydrogel and insulating elastomers . Copyright 2021, ACS Publications; (E) (i) Surface modification process of CsPbBr
3
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perovskite with silica, and (ii) fabricated perovskite-based stretchable luminescent devices . Copyright 2021, Elsevier; (F) (i)
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Fabrication process of stretchable QLED devices, and (ii) operation at strain of 0% and 70% . Copyright 2017, ACS Publications; (G)
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(i) Structure of stretchable Pe-QD LED, and (ii) operation at strain of 0% and 50% . Copyright 2019, Wiley-VCH. PLED: Polymer-type
light-emitting diode; ACEL: alternative current electroluminescence; EL: electroluminescent; PEDOT:PSS: poly(3,4-
ethylenedioxythiophene) polystyrene sulfonate; PAAm: polyacrylamide; QLED: quantum dot light-emitting diode.
interactions, thereby imparting stretchable properties to the ion-gels.
Inorganic phosphor-based emissive materials
Stretchable alternative current electroluminescence (ACEL) based on inorganic phosphors is a promising
component for wearable electronic devices and soft robotics. von Szczepanski et al. aimed to improve the
high operating voltage of ACEL by increasing the relative permittivity of the elastomer in the emissive
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layer . They synthesized a polysiloxane dielectric elastomer with cyanopropyl side groups and
incorporated inorganic ZnS phosphors to fabricate the ACEL device. The synthesized polar elastomer
exhibited a dielectric constant (~11.5) four times higher than commercial PDMS. The ACEL device
fabricated using this elastomer showed a maximum luminance of 790 ± 31 cd·m at an electric field of
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2.5 V·μm and a frequency of 60 kHz. Additionally, by utilizing AgNW-based stretchable electrodes,
uniform light emission was maintained even under strain up to 50% [Figure 10C]. Similarly, as another
example of a stretchable electroluminescence (EL) device based on ZnS phosphors, Zhu et al. proposed a 3D
printing technique that integrates PEDOT:PSS-PAAm hydrogel and poly(2-hydroxyethyl acrylate) (PHEA)
insulating elastomer without additional assembly processes . They reported the development of an EL
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device by incorporating ZnS phosphor particles into the fabricated elastomer matrix. The fabricated EL
device achieved an operating electric field threshold of 1.5 V·μm at a frequency of 1 kHz and the maximum
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luminance of ~35 cd·m was achieved at 3.5 V·μm beyond the operating threshold. Additionally, the
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incomplete polymerization at the interface between the hydrogel and PHEA dielectric elastomer layers