Multi-layer encapsulation structures for stable bottom- and top-emitting white OLED devices

Area of Science:

• Materials Science
• Optoelectronics
• Device Engineering

Background:

• Organic Light-Emitting Diodes (OLEDs) suffer from poor environmental stability, thermal tolerance, and material decomposition.
• Existing encapsulation methods often fail to provide comprehensive protection against these degradation factors.

Purpose of the Study:

• To develop and evaluate a novel multi-layer encapsulation structure for white OLED devices.
• To enhance the environmental stability, thermal tolerance, and operational lifetime of both top- and bottom-emitting OLEDs.
• To maintain high light transmittance through the encapsulation layers.

Main Methods:

• Fabrication of white OLEDs using stacked tricolor luminescent materials.
• Construction of a multi-layer encapsulation system including heat-conductive films, inorganic barrier layers, transparent glues, POSS resin, and transparent films/glasses.
• Implementation of a three-dimensional protection strategy involving environmental isolation, stress buffering, and thermal management.
• Characterization of device performance, including external quantum efficiency (EQE) and light decay over time under accelerated testing.

Main Results:

• Encapsulated top-emitting OLEDs achieved an EQE of 11.6%, and bottom-emitting OLEDs achieved 7.5%.
• The designed encapsulation significantly reduced light decay compared to unencapsulated devices.
• After 720 hours, encapsulated devices showed only 16-20% decay, while unencapsulated devices exceeded 40% decay.

Conclusions:

• The developed multi-layer encapsulation effectively addresses the stability issues of white OLED devices.
• The three-dimensional protection system enhances device longevity and reliability under operational stress.
• This encapsulation strategy is crucial for advancing the commercial viability of high-performance white OLEDs.