Hybrid Liquid Metal Cathode Enables High‐Performance Intrinsically Stretchable OLEDs

ABSTRACT Intrinsically stretchable light‐emitting diodes (LEDs) are essential for next‐generation wearable and implantable optoelectronics. However, achieving high‐performance in intrinsically stretchable LEDs remains elusive due to the absence of a stretchable cathode that concurrently ensures efficient electron injection, mechanical compliance, and high optical reflectance. Here, we introduce a hybrid liquid metal—liquid metal particle (Hyb‐LM) cathode, engineered by selective rupture of surface liquid metal particles (LMPs), which facilitates their transformation into a continuous liquid metal (LM) layer. The resulting bilayer structure, comprising a surface LM layer and an underlying LMP layer, exhibits an exceptional combination of low work function (∼4.1 eV), high reflectance (∼90%), low sheet resistance (2.70 × 10 − 2 Ω sq −1 ), and negligible resistance changes under 150% strain (R/R 0 = 1.03 at 150% strain), overcoming fundamental limitations in state‐of‐the‐art stretchable cathodes. The Hyb‐LM cathode enables the realization of intrinsically stretchable organic LEDs with a low turn‐on voltage of 3.0 V, a maximum luminance of 17 670 cd m −2 , and a record‐high current efficiency of 10.35 cd A −1 , representing a critical advancement toward stretchable displays and implantable optoelectronics.