High‐Permittivity Polysiloxanes for Bright, Stretchable Electroluminescent Devices

Abstract

Stretchable alternating current electroluminescent (ACEL) devices have a bright future in wearable electronics and soft robotics. Still, their market application is hindered by high operating voltages. The voltage can be reduced by increasing the relative permittivity of the dielectric elastomer in the emissive layer. Here, a fluorine‐free high‐permittivity silicone elastomer functionalized with cyanopropyl side groups, specially designed for application in stretchable ACEL devices, is introduced. The polar silicone elastomer exhibits excellent mechanical properties and a dielectric permittivity four times higher than commercial PDMS. Light‐emitting devices based on the polar elastomer reach 7.5 times higher maximum luminance at the same electric field than PDMS‐based devices and turn on at a 50% lower electric field. Besides, the polar elastomer‐based devices perform better than all materials tested in literature in achieving high luminance at low electric fields. Stretchable ACEL devices are built from the polar elastomer which shows bright and uniform light emission and can be operated up to 50% strain. The high‐permittivity silicones are promising materials for stretchable ACEL devices and can help their breakthrough to market application by overcoming the drawback of high operating voltages.

Low Driving Voltage Electroluminescence Device for Integrated Visual Strain Sensing

“…Flexible ACEL display devices operate on the high-field principles, often requiring hundreds or even thousands of volts to achieve satisfactory brightness (∼100 cd/m 2 ). − For user safety, it is crucial to ensure low driving voltage in wearable devices. Additionally, a low operating voltage reduces power consumption, simplifies the device’s driving system integration, and lowers associated costs. − To achieve lower driving voltage in ACEL devices, materials with higher dielectric properties and more compact device structures are required. − Doping flexible substrates with ceramic powders such as BaTiO 3 (BTO), CaTiO 3 , and PbTiO 3 is a well-established method for enhancing dielectric properties. ,,− Additionally, polymer materials like polyvinylidene difluoride (PVDF) have replaced traditional organic silicone materials, offering higher dielectric properties. ,, However, it is noteworthy that the reported PVDF-based ACEL devices struggle to get rid of the reliance on strong polar solvents such as N , N -dimethylformamide and acetone. ,, Simultaneously, optimization of the device structure also advanced rapidly. The dielectric layer serves as the primary structure in ACEL display devices to prevent electrical breakdown.…”