Development of electron-flow-strengthened azo dyes with a wide color reproduction range for application in the color conversion layers of microdisplays

Abstract

In this study, we developed novel red azo dyes applicable to color conversion layers with a wide color reproduction range, utilized in micropixel white organic light- emitting diodes. We introduced strong electron-withdrawing groups at the diazo component with the aim of controlling electron flow within the molecules and achieving a superior molar absorption coefficient. The introduction of these groups also resulted in a decrease in the lowest unoccupied molecular orbital energy level, leading to a red shift in the absorption wavelength, thus anticipating a broader color reproduction range. Subsequently, we prepared the color resists by combining the novel red azo dyes with a low-temperature-curing binder, producing color conversion films through spin coating. These spin-coated films exhibited high transmittance of up to 99 %, indicating the optimal formulation of the color resist components. Additionally, the introduction of a yellow color-tuning dye, structurally similar to the novel red dyes, broadened the color reproduction range to 111 % of the National Television System Committee color coordinates. The photostability tests conducted on the prepared spin-coated films exhibited minuscule variations in transmittance, indicating the simultaneous enhancement of the optical properties and photostability of the prepared microdisplay color conversion layers.