Vacuum-Evaporated, Lead-Free RbYbI₃ Perovskite Interlayers for Universal Electron Injection in High-Performance...

Area of Science:

• Materials Science
• Organic Electronics
• Solid State Physics

Background:

• Charge injection barriers at electrode-organic interfaces limit OLED performance.
• Conventional electron injection layers (EILs) like LiF have limitations, especially with certain metals.
• Efficient charge balance is crucial for high-performance organic light-emitting diodes (OLEDs).

Purpose of the Study:

• To introduce a lead-free perovskite, RbYbI₃, as a novel and efficient electron injection layer (EIL) for OLEDs.
• To investigate the mechanism by which RbYbI₃ improves electron injection and device performance.
• To demonstrate the compatibility and advantages of RbYbI₃ over conventional EILs.

Main Methods:

• Thin film deposition of RbYbI₃ via vacuum evaporation.
• Surface potential measurements to quantify interface modification.
• First-principles density functional theory (DFT) calculations to understand surface dipole formation.
• Fabrication and characterization of blue and green OLED devices with RbYbI₃ EILs.

Main Results:

• A 5-nm RbYbI₃ layer induced a 630-mV surface potential shift, lowering the injection barrier.
• DFT calculations confirmed termination-dependent surface dipoles in RbYbI₃.
• OLEDs with RbYbI₃ showed lower turn-on voltage and higher external quantum efficiency (EQE) compared to LiF controls.
• RbYbI₃ demonstrated compatibility with both aluminum and silver cathodes.

Conclusions:

• Lead-free perovskite RbYbI₃ is a highly effective EIL for OLEDs, improving electron injection.
• RbYbI₃ offers a universal and practical alternative to conventional EILs, overcoming electrode-material limitations.
• This perovskite-based EIL strategy facilitates the development of next-generation high-performance OLED devices.