Acquiring High‐Performance Deep‐Blue OLED Emitters through an Unexpected Blueshift Color‐Tuning Effect Induced by Electron‐Donating ‐OMe Substituents

Abstract

A series of blue-emissive 7-(diphenylamino)-4-phenoxycoumarin derivatives bearing -CF , -OMe, or -N(Me) substituents on the phenoxy subunit were synthesized. Although both the -CF and -N(Me) modifications were found to trigger redshifted fluorescence, the -OMe substitution was demonstrated to exert an unexpected blueshift color-tuning effect toward the deep-blue region. The reason is that the moderate electron-donating -OMe group can endow coumarins with unaltered HOMO but elevated LUMO energy levels. Moreover, the -OMe substitution was found to be beneficial to the thermal stability of these coumarins. Therefore, the trimethoxy-substituted objective compound can act as a high-performance deep-blue organic light-emitting diode (OLED) emitter, and OLED based on it emits deep-blue light with CIE coordinates of (0.148, 0.084), maximum luminance of 7800 cd m , and maximum external quantum efficiency of 5.1 %. These results not only shed light on the molecular design strategy for high-performance deep-blue OLED emitters through color-tuning, but also show the perspective of coumarin derivatives as deep-blue OLED emitters.

Linear Coumarinacenes Beyond Benzo[g]coumarins: Synthesis and Promising Characteristics

“…[ 1 ] Structurally simple derivatives of coumarin exhibit rich photophysical and photochemical properties (high photoluminescence quantum yields, large Stokes shifts and good photostability) paving their entry into modern photonic applications; laser dyes, [ 3a,3b ] non‐linear optics, [ 3c ] two‐photon bioimaging [ 3d ] and sensing [ 3e ] are some examples. Moreover, coumarin derivatives are recently being exploited as functional materials in organic light emitting devices, [ 4a,4b ] liquid crystals, [ 4c ] dye‐sensitized solar cells, [ 4d,4e ] electron and energy transfer systems, [ 4f,4g ] and fluorescent probes. [ 4h ] Despite the broad utility of coumarins, the low‐lying absorption and emission wavelengths (due to shorter conjugation lengths) are primarily the bottlenecks in furthering their applications.…”

“…Moreover, coumarin derivatives are recently being exploited as functional materials in organic light emitting devices, [ 4a,4b ] liquid crystals, [ 4c ] dye‐sensitized solar cells, [ 4d,4e ] electron and energy transfer systems, [ 4f,4g ] and fluorescent probes. [ 4h ] Despite the broad utility of coumarins, the low‐lying absorption and emission wavelengths (due to shorter conjugation lengths) are primarily the bottlenecks in furthering their applications.…”

OLED display application of 2-(6-Fluoro-2-oxo-2H-chromen-4-ylmethoxy)-benzoic acid methyl ester derivative

“…Thus, the 2-FBME possesses high color purity and good CIE chromaticity coordinate also they would have potential application of organic light emitting devices, this simple method is to produce the blue light as blue component can play important role. The calculated chromaticity coordinates for 2-FBME in chloroform are near to standard chromaticity (NTSC) for excellent blue color and thus are promising blue producers for WLED application [8][9][10] . Where, (X, Y) are CIE chromaticity coordinate values of studied compound, (Xi, Yi) is the color coordinate of white illumination and (Xd, Yd) is the CIE coordinate of the dominant emission wavelength.…”

New 3-Ethynylaryl Coumarin-Based Dyes for DSSC Applications: Synthesis, Spectroscopic Properties, and Theoretical Calculations

“…The push-pull effect in these D-π-A dyes leads to efficient intramolecular charge transfer (ICT) from the donor to the acceptor unit through the π-bridge upon light absorption. Among the many classes of organic compounds used, coumarins are of particular interest due to their wide use as fluorescent sensors [17][18][19], emitting layers in Organic Light-Emitting Diodes (OLEDs) [20][21][22] and in laser applications [23,24], owing to their large Stokes shift, high quantum yields and good solubility. Additionally, their photophysical properties can be easily tuned through the addition of substituents, namely electron-withdrawing substituents in position 3 and electron-donating substituents in position 7 [25].…”