Origin of exciplex degradation in organic light emitting diodes: Thermal stress effects over glass transition temperature of emission layer

Inyeob Na, Ki Ju Kim, Gyu Tae Kim, Youkyung Seo, Yeeun Kim, Young Kwan Kim, Min Kyu Joo

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    13 Citations (Scopus)

    Abstract

    Exploiting exciplexes in organic light-emitting diodes (OLEDs) to enhance electroluminescence lifetime and quantum efficiency is of considerable interest to researchers. The presence of exciplexes has been demonstrated in a host material interface in a multiple stacked OLED; therefore, understanding the degradation mechanism of exciplexes and host materials is essential to develop highly reliable and uniform OLEDs. Herein, we report thermal stress-driven exciplex degradation in a blue OLED, which comprises 4,4′-bis(N-carbazolyl)-,1′-biphenyl (CBP) as a host material without dopants. The device structure dependent-electroluminescence clearly confirms the formation of exciplexes surrounding the CBP interfaces at 398 and 450 nm, respectively. During the thermal stress over the glass transition temperature (Tg) of the CBP, the spectral intensity of the exciplex decreased significantly, and the ideality factor and characteristic trap energy increased abruptly when the thermal stress temperature was higher than the Tg of CBP, signaling the origin of thermal degradation effects on the exciplex and host material in our OLED.

    Original languageEnglish
    Article number063303
    JournalApplied Physics Letters
    Volume117
    Issue number6
    DOIs
    Publication statusPublished - 2020 Aug 10

    Bibliographical note

    Funding Information:
    This study was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (No. 2015R1A6A1A03031833, Y.K.K.) and also supported by the Korea government (MSIP) (Nos. NRF-2019R1C1C1003467 and NRF-2019K2A9A1A06083674, M.-K.J.).

    Publisher Copyright:
    © 2020 Author(s).

    ASJC Scopus subject areas

    • Physics and Astronomy (miscellaneous)

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