Isotope Effect of Host Material on Device Stability of Thermally Activated Delayed Fluorescence Organic Light‐Emitting Diodes. Issue 4 (7th February 2021)

• Record Type: Journal Article
• Authors: Liu, Xuelong; Chan, Chin-Yiu; Mathevet, Fabrice; Mamada, Masashi; Tsuchiya, Youichi; Lee, Yi-Ting; Nakanotani, Hajime; Kobayashi, Shinichiro; Shiochi, Masayuki; Adachi, Chihaya
• Is Part Of: Small science. Volume 1:Issue 4(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-02-07
• Subjects: deuteration of organic functional materials -- isotope effects -- operational stability -- organic light-emitting diodes -- thermally activated delayed fluorescence; Nanoscience -- Periodicals; Nanotechnology -- Periodicals; 620.5
• DOI: 10.1002/smsc.202000057
• Languages: English
• ISSNs: 2688-4046

Abstract

Abstract : Organic light‐emitting diodes (OLEDs) exhibiting thermally activated delayed fluorescence (TADF) have attracted great interest because of their excellent exciton harvesting ability in electroluminescence (EL). While TADF‐OLEDs show a high EL efficiency, the device operational stability is not necessarily satisfactory for commercial applications. Herein, the isotope effect of the host material on the device operational stability in TADF‐OLEDs is investigated. It is unveiled that the deuterated host, i.e., PYD2Cz‐ d 16, forms a denser film than that of the nondeuterated host, PYD2Cz, demonstrating enhanced stable amorphous nature and balanced carrier transport properties. In green TADF‐OLEDs, the PYD2Cz‐ d 16 ‐based OLED considerably lengthens the device operational stability of LT95 (95% of the initial luminance) to ≈140 h at an initial luminance of 1000 cd m −2, which is 1.7 times longer than that of PYD2Cz. Device stabilities of blue TADF‐OLEDs with PYD2Cz‐ d 16 as a host are also demonstrated with an enhancement of 2 times in LT50 at an initial luminance of 1000 cd m −2 . It is suggested that the deuterated materials have a positive effect on the device stability in not only TADF‐OLEDs, but also all other OLEDs having fluorescence and phosphorescence emitters. Abstract : A deuterated host (PYD2Cz‐ d16 ) is introduced in thermally activated delayed fluorescence organic light‐emitting diodes (TADF–OLEDs). Using deuterated host, the lifetime of TADF OLEDs is extended. Such improvements could be attributed to the noncrystalline and densely packed behaviors of film state in deuterated host, resulting in much more balanced carrier‐transporting properties in devices.