Stamped Liquid Metal Cathode for High-Efficiency Intrinsically Stretchable OLED

Intrinsically stretchable light-emitting diodes are essential to realize free-form electronics for wearable electronics or bioelectronics applications. However, all the intrinsically stretchable light-emitting diodes reported to date have poor performances, including low external quantum efficiency and high driving voltage, due to the absence of stretchable cathode which enables efficient electron injection. Here, I present stamped liquid metal (SLM) cathode having advantages of both liquid metal particles and bulk liquid metal. SLM has low sheet resistance, negligible resistance changes under strain, high reflectance, and low work function, which are the ideal materials properties for stretchable cathodes. I utilized SLM to realize highly efficient intrinsically stretchable light-emitting diodes having low turn-on voltage (3.0 V), high efficiency (3.5%), and high luminance (17,600 cd m^-2).