Organic light-emitting diodes with a single emissive layer of 3, 6-di-tert-butyl-carbazolyl-disubstituted trifluoromethyl benzene showing an ultra-broad white electroluminescence spectrum. (April 2023)

• Record Type: Journal Article
• Authors: Keruckiene, Rasa; Lin, Bo-Yen; Chen, Chia-Hsun; Chu, Chun-Chieh; Lin, Chi-Feng; Volyniuk, Dmytro; Chiu, Tien-Lung; Lee, Jiun-Haw; Grazulevicius, Juozas V.
• Is Part Of: Dyes and pigments. Volume 212(2023)
• Publication Date: 2023-04
• Subjects: Carbazole -- OLED -- Exciplex -- Ultraviolet -- White; Dyes and dyeing -- Periodicals; Pigments -- Periodicals; 667.2
• DOI: 10.1016/j.dyepig.2023.111133
• Languages: English
• ISSNs: 0143-7208

Abstract

Abstract: 3, 6-Di- tert -butyl-carbazolyl disubstituted trifluoromethyl benzene was obtained by single-step synthesis. The compound showed high glass transition temperature of 138 °C. It also exhibited bipolar charge transport with hole mobility of 3.38 × 10 −3 cm 2 /Vs at electric field of 4.87 × 10 5 V/cm and electron mobility of 2.44 × 10 −4 cm 2 /Vs at the electric field of 5.3 × 10 5 V/cm. The compound was used in OLEDs as a multifunctional emitter. It appeared to be applicable in UV to white fluorescent devices. A simple three-layers OLED with pristine emitter layer was manufactured and showed a particular property, i.e. voltage-tuneable emission, which varied from the UV to the white one. On the basis of 3, 6-di- tert -butyl-carbazolyl disubstituted trifluoromethyl benzene, UV-emitting OLED was obtained that showed a particular feature i.e. voltage-tuneable an ultra-broad spectrum emission from UV (350 nm) to IR (780 nm), whose spectrum is the broadest compared to the reported single molecular emission. At low voltage of 5 V, the device showed electroluminescence in the UV region with a single peak of electroluminescence spectrum at 388 nm and a full width at half maximum (FWHM) bandwidth of 60 nm. After increasing the driving voltage, the device became a white-OLED. In addition, as acceptor of exciplex emitting layer of device, the high-efficiency blue exciplex emission-based OLED ( λ e m = 490 nm) with external quantum efficiency of 9.1% was demonstrated using exciplex-forming system consisting of 3, 6-di- tert -butyl-carbazolyl-disubstituted trifluoromethyl benzene and PO-T2T (1:1). The external quantum efficiency value of the exciplex-based OLED was superior compared to those of the previously reported pure exciplex emission-based OLEDs. Highlights: New efficient carbazolyl disubstituted trifluoromethyl benzene is presented. It exhibits bipolar charge transport of 10 −3 cm 2 /Vs at strong electric fields. It's emission is voltage-tuneable and can vary from the UV to the white one in OLED. Blue exciplex based OLED with newly presented donor exhibited EQE of 9.1%.