Dark spot growth and the acceleration factor in flexible organic light-emitting diodes (February 2019)

Takeru Okada, Ayako Yoshida, Makoto Matsukawa, Taishi Tsuji

Dark spots (DS) growth and its acceleration factor under high temperature and high humidity condition were measured and modeled using flexible organic light-emitting diodes (OLEDs) with a single-layered barrier, and a multilayered barrier respectively. In OLEDs with a single-layered barrier, the time evolution of the DS and the edge shrink were explained by the same water permeation model, and the acceleration factor was the same between DS and edge shrink. The acceleration factor of OLEDs with a double-layered barrier was the same with that of a single-layer barrier, but the DS expanded after the delay time in case of OLEDs with a triple-layered barrier. The acceleration factor of the DS growth rate was proportional to relative humidity at a constant temperature, and it showed Arrhenius temperature dependence. On the other hand, the acceleration factor of the delay time was smaller than that of the growth rate because it was independent on humidity. No growing DS was observed in developed flexible OLED panels with the high-reliability barrier substrate after storage for 8000 hours under 85℃/85%RH condition. Consequently, it can be estimated that it corresponds to storage for more than 30 years under 25℃/50%RH condition.

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