Hybrid Liquid Metal Cathode Enables High-Performance Intrinsically Stretchable OLEDs

Area of Science:

• Materials Science
• Optoelectronics
• Nanotechnology

Background:

• Intrinsically stretchable light-emitting diodes (LEDs) are crucial for advanced wearable and implantable devices.
• Current stretchable LEDs face performance limitations due to inadequate cathode materials that fail to provide efficient electron injection, mechanical flexibility, and optical reflectance.

Purpose of the Study:

• To engineer a high-performance, intrinsically stretchable cathode for organic LEDs.
• To overcome the limitations of existing stretchable cathode technologies.

Main Methods:

• Development of a hybrid liquid metal-liquid metal particle (Hyb-LM) cathode.
• Engineered selective rupture of surface liquid metal particles (LMPs) to form a continuous liquid metal (LM) layer.
• Characterization of the bilayer structure's electrical, optical, and mechanical properties.

Main Results:

• The Hyb-LM cathode demonstrated a low work function (~4.1 eV), high reflectance (~90%), and low sheet resistance (2.70 × 10^-2 Ω sq^-1).
• The cathode maintained negligible resistance changes under 150% strain (R/R₀ = 1.03).
• Stretchable organic LEDs fabricated with the Hyb-LM cathode achieved a low turn-on voltage (3.0 V), high luminance (17,670 cd m^-2), and record current efficiency (10.35 cd A^-1).

Conclusions:

• The novel Hyb-LM cathode significantly advances the performance of intrinsically stretchable LEDs.
• This development is a critical step towards realizing practical stretchable displays and sophisticated implantable optoelectronic systems.