Bright Bifacial White‐Light Illumination by Highly Deformable Electroluminescent Devices Based on Transparent Ionic‐Hydrogel Electrodes and Quantum‐Dot Color Conversion

Deformable alternating‐current electroluminescent (ACEL) devices are of increasing interest because of their potential to drive innovation in soft optoelectronics. Despite the research focus on efficient white ACEL devices, achieving deformable devices with high luminance remains difficult. In this study, this challenge is addressed by fabricating white ACEL devices using color‐conversion materials, transparent and durable hydrogel electrodes, and high‐k nanoparticles. The incorporation of quantum dots enables the highly efficient generation of red and green light through the color conversion of blue electroluminescence. Although the ionic‐hydrogel electrode provides high toughness, excellent light transmittance, and superior conductivity, the luminance of the device is remarkably enhanced by the incorporation of a high‐k dielectric, BaTiO3. The fabricated ACEL device uniformly emits very bright white light (489 cd m−2) with a high color‐rendering index (91) from both the top and bottom. The soft and tough characteristics of the device allow seamless operation in various deformed states, including bending, twisting, and stretching up to 400%, providing a promising platform for applications in a wide array of soft optoelectronics. A bifacial white light alternating current electroluminescent device is fabricated by introducing quantum dots that convert blue electroluminescence into red and green photoluminescence. The fabricated device exhibits a high luminance of 489 cd m−2 with a color rendering index of 91 and operates stably in highly deformed states, such as bending, twisting, and stretching.