Methacrylate-Functionalized BaTiO3 for High-Luminance Stretchable Alternating-Current Electroluminescent Devices

Blending a high-permittivity ceramic such as barium titanate (BTO) into the emission layer is an established route to brighter alternating-current electroluminescent (ACEL) devices, but the hydrophilic ceramic aggregates in silicone elastomers and caps the loading attainable in a thin stretchable layer. BTO nanoparticles were modified with 3-(trimethoxysilyl)propyl methacrylate through an acid-catalyzed sol–gel reaction that leaves a thin methacrylate shell on the particle surface. The modified filler (m-BTO) dispersed uniformly in the elastomer and entered blade-coated emission layers at loadings beyond the reach of the bare particles. The m-BTO composites increased the dielectric constant of the emission layer more efficiently than the BTO composites while retaining or improving the stretchability. The resulting ACEL devices were about 30% brighter than the BTO devices at equal loading. The accessible 25 wt % loading increased the peak luminance to 515 cd/m2 at 400 V and 30 kHz, 2.7 times that of the phosphor-only device, with the blue emission color unchanged. The devices operated under twisting, folding, and stretching and sustained emission to 500% strain.