Understanding Dark Spot Formation and Growth in Organic Light-Emitting Devices by Controlling Pinhole Size and Shape

Abstract

We report on our in‐situ experimental observations of dark spots in organic light‐emitting diodes using optical microscopy. Uniformly sized silica microparticles are used to intentionally create size‐ and shape‐controllable pinholes on the cathode protective layer. Subsequently, the pinholes trigger the initial formation of dark spots, which we then monitor. Due to the use of particles of various diameters, we are able to linearly associate the growth rate with pinhole size. This allows us to estimate the original pinhole sizes that give rise to the dark spots and to study their distribution. Our studies verify that pinholes on the protective layer create pathways for water or oxygen diffusion, which controls the dark spot growth rate. The pinhole size dependence illustrates that the pinhole perimeter (not the area) determines the amount of water or oxygen diffusing into the diodes at a certain time.

X-ray and neutron reflectivity measurements of moisture transport through model multilayered barrier films for flexible displays

“…3 The primary shortcoming of most OLEDs is poor environmental stability that results in nonemissive regions upon extended exposure to ambient conditions. The degradation in performance is a result of the oxidation and delamination of the metal cathode 4 and the chemical reaction of the organic layer from exposure to moisture and oxygen. OLED lifetimes can be extended by orders of magnitude by device encapsulation.…”

New hybrid encapsulation for flexible organic light-emitting devices on plastic substrates

“…The key issue in achieving durable flexible OLEDs on plastic substrates is to protect them from moisture and oxygen as OLEDs are very sensitive to both [13][14][15] . The luminance decay curve of the device with our new hybrid encapsulation is shown in Figure 3.…”

Investigation of Solution-Processed Ultrathin Electron Injection Layers for Organic Light-Emitting Diodes

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