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.|A high-permittivity, nitrile-functional silicone elastomer for application in stretchable electroluminescent devices is introduced. The polar elastomer emissive layer reaches significantly higher luminance and needs lower operating voltages than an emissive layer based on commercially available PDMS. Besides, the polar elastomer can be used to build bright and stretchable devices in a simple bottom-up procedure. image