Quantitative Analysis of Degradation Factors in Blue-Fluorescent Organic-Light-Emitting Diodes

초록

The degradation mechanism of blue-fluorescent organic-light-emitting diodes (OLEDs) has been continuously studied to overcome their limited operational lifetime. However, studies thus far have focused primarily on only one critical factor after a sufficiently long progression of degradation, such as the time to reach 50% of initial luminance (LT50). However, due to the sensitivity of human eyes, only 3-5% of luminance changes can be recognized. Thus, research on early-stage degradation is needed from a more practical viewpoint. Herein, we propose a new methodology to analyze the factors affecting early-stage degradation, such as LT97 in blue-fluorescent OLEDs. The result is expressed numerically (or quantitively) and subdivided into three factors in total, including bleaching of organic materials, quenching in excited states, and variations in charge balance. It was found that throughout early-stage degradation, the bleaching of emissive materials and the quenching of excitons adversely affect a device’s operational stability. However, interestingly, the degree of charge balance slightly enhances up to LT97 and thereafter deteriorates. Degradation factors are further investigated up to LT88. The methodology presented here can be further expanded to analyze degradation factors quantitatively across various OLED stages and colors. © 2023 American Chemical Society

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