Collaboration identifies degradation of blue OLEDs

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The degradation of blue organic light-emitting diodes (OLEDs) is better understood following research by scientists at the National Physical Laboratory (NPL) and the Samsung Advanced Institute of Technology (SAIT).

Close-up of the OrbiSIMS instrument’s vacuum chamber showing the nozzles of the ion beams and electrode that extract ionised molecules for analysis
Close-up of the OrbiSIMS instrument’s vacuum chamber showing the nozzles of the ion beams and electrode that extract ionised molecules for analysis - NPL

Understanding the degradation mechanism of blue OLEDs is essential to improve their performance and stability, but the degradation mechanisms that cause blue OLEDs to fail are still not yet fully understood. This limits the stability of blue OLEDs, and by extension the lifetime of OLED technology in full colour display screens and lighting.

The first polymer light-emitting diode (PLED), created at NPL in 1975, used a polymer film of up to 2.2µm thick located between two charge-injecting electrodes. Since then, developments in red and green OLED technology resulted in these coloured OLEDs being comparable now to conventional LEDs.

OLEDs are formed of very thin layers of organic molecules, and chemically sampling nanoscale organic layers and interfaces with enough analytical information is challenging.

To tackle this, the NPL/SAIT team used OrbiSIMS, a mass spectrometry imaging technique invented at NPL in 2017. The team used OrbiSIMS’ nanoscale mass spectrometry to identify, for the first time, degradation molecules of blue OLEDs with exceptional sensitivity and localise them with 7nm depth resolution within the OLEDs multi-layered architecture.

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blue OLEDs