[22p-E206-1~11] 12.4 Organic light-emitting devices and organic transistors

[22p-E206-11] Organic Light-Emitting Diodes Based on Interfacial Upconversion Opperated by Extremely Low Driving Voltage

〇Seiichiro Izawa^1,2,3, Masahiro Morimoto⁴, Shigeki Naka⁴, Masahiro Hiramoto^1,2 (1.IMS, 2.SOKENDAI, 3.JST PRESTO, 4.Univ. Toyama)

Keywords:Organic semiconductor, Interface, Upconversion

A remaining frontier in the field of organic light-emitting diodes (OLEDs) is reducing their operating voltage. Herein, we report an efficient OLED, operable by a 1.5-V battery, that produces bright emission equivalent to luminance of a typical display. The OLED have a smaller turn-on voltage at 0.97 V than an optical energy of emitted photons at 2.04 eV (608 nm), because the OLED is based on upconversion (UC) transition associated with triplet–triplet annihilation that doubles the energy of excited states. We reveal that the characteristics of charge transfer (CT) state at the interface are key to efficient UC, and the percentage of excited states deactivated by parasitic loss processes during the UC transition is significantly reduced from over 90% to approximately 10% by introducing a highly crystalline acceptor material and an emissive dopant. Consequently, the UC-OLED achieves a quantum efficiency that is two orders of magnitude higher than that in the previous report.