Air-stable flexible organic light-emitting diodes enabled by atomic layer deposition

Area of Science:

• Materials Science
• Device Physics
• Nanotechnology

Background:

• Organic Light-Emitting Diodes (OLEDs) offer energy-efficient lighting and display solutions.
• Limited air-stability of flexible OLEDs hinders practical applications.
• Developing robust encapsulation and electron-injection layers is crucial for device longevity.

Purpose of the Study:

• To demonstrate air-stable flexible OLEDs using atomic-layer-deposited (ALD) films.
• To investigate the role of ZnO as an electron-injection layer (EIL) and gas barrier.
• To evaluate an Al2O3/ZnO (AZO) nano-laminated film for device encapsulation.

Main Methods:

• Utilized two-dimensional atomic-layer-deposition (ALD) for fabricating ZnO and AZO films.
• Analyzed film morphology, electrical properties, and gas permeation (WVTR).
• Employed low ALD temperatures (70 °C) to prevent thermal damage to OLEDs.

Main Results:

• Optimized ZnO EIL performance and gas barrier properties at 70 °C ALD.
• Achieved excellent gas barrier properties with WVTR <5 × 10(-4) g m(-2) day(-1) for both ZnO and AZO films.
• Demonstrated an air-storage lifetime exceeding 10,000 hours for flexible OLEDs.

Conclusions:

• Low-temperature ALD is effective for creating air-stable flexible OLEDs.
• ZnO and AZO films provide efficient electron injection and superior gas barrier functionalities.
• This approach overcomes thermal degradation issues, significantly improving OLED operational lifetime.