Positional Isomers of Phenylacridine/Spirobifluorene as Deep-Blue Fluorescent Emitters for Organic Light-Emitting Diodes

Designing deep-blue fluorophores with a low CIEy is an important request for organic light-emitting diode (OLED) technology either for display applications or to develop new applications such as light source with antibacterial properties. The challenge of deep-blue emitting OLEDs mainly relies on the difficulty to reach efficient emitters fulfilling all the characteristics desired to insure a high device performance with suitable CIE coordinates. Herein, we report on the synthesis, the physico-chemical properties and the application as emissive layer in an OLED of two deep-blue emitters constructed on the association of Spirofluorene-N-PhenylAcridine (SPA-F) and SpiroBiFluorene (SBF) molecular fragment. Two emitters, 2,2-SPAF-SBF and 2,3-SPAF-SBF have been constructed following a similar design strategy. The emission wavelength is tuned by the substitution pattern of the SBF backbone (meta or para linkage). Through a structure/properties relationship study, the electrochemical, photophysical and thermal/morphological properties are discussed. When used as emitter in a multi-layer OLED, 2,2-SPA-SBF displays a deep-blue emission reaching an EQE of & AP;1.7% and a V-on of 4 V. The electroluminescent spectrum displays a & lambda;(max) below 400 nm (i.e. 394 nm) and CIE coordinates of (0.182, 0.054). The CIEy coordinate of 0.054 is low and fits the NTSC and EBU standards.