Trindade, G; Sul, S; Kim, J; Havelund, R; Eyres, A; Park, S; Shin, Y; Bae, H J; Sung, Y M; Matjacic, L; Jung, Y; Won, J; Jeon, W S; Choi, H; Lee, H S; Lee, J-C; Kim, J-H; Gilmore, I S (2023) Direct identification of interfacial degradation in blue OLEDs using nanoscale chemical depth profiling. Nature Communications, 14. 8066

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Abstract

Understanding the precise degradation mechanism of organic electronic devices such as organic light-emitting diodes (OLED) is essential to improve device performance and stability. OLED failure, if not process-related, arises mostly from chemical instability. However, the challenges of sampling from nanoscale organic layers and interfaces with enough analytical information has hampered identification of degradation products and degradation mechanisms. Here, we present a precise diagnostic method of OLED degradation using an Orbitrap mass spectrometer equipped with a gas cluster ion beam to gently desorb nanometre levels of materials, providing molecular information with 7-nm depth resolution and over 120,000 mass resolving power. We measured blue phosphorescent OLED devices, and showed that dominant chemical degradation occurred at the interface between electron transport and emission layers (EML/ETL) where exciton distribution was maximised and reaction products accumulated with the level of degradation, resulting in an increase of the device impedance and driving voltage. We also show that an increased lifetime of a device with slightly modified host material results from less accumulated degradation products. We demonstrate a precise diagnostic tool of OLED devices, with an unprecedented depth resolution, which provides guidance for material and device architecture development.

Item Type:	Article
Keywords:	OrbiSIMS; OLED
Subjects:	Nanoscience > Surface and Nanoanalysis
Divisions:	Chemical & Biological Sciences
Identification number/DOI:	10.1038/s41467-023-43840-9
Last Modified:	04 Jul 2024 14:20
URI:	https://eprintspublications.npl.co.uk/id/eprint/9981