Thermal and barrier properties of liquid getter-filled encapsulations for OLEDs

We investigate the thermal and barrier properties of liquid getter-filled glass encapsulations for organic light-emitting diodes (OLEDs). A conventional glass encapsulation has a protective hollow where nitrogen gas resides. Such a configuration stores heat that causes damage to OLED devices. To dissipate heat, we have filled a hollow glass cap with a UV curable liquid getter, transferring heat from the device to the glass cap where a flexible heat sink is attached. With this scheme, however, heat is reduced only by 15.5 °C (from 62.3 to 46.8 °C), even though it is larger than that (7.7 °C) of OLED based on the conventional glass encapsulation. We have found that there still exists a N2 gas-filled gap, which appears during UV-curing of the liquid getter. To eliminate it, we have coated a liquid getter on a flat glass cap and then encapsulated the OLED device with it. This scheme dissipates heat by 27.7 °C (from 60.5 to 32.8 °C), yet it causes some damage to organic layers when the moisture getter absorbs out-gases, generating dark spots and thus shortening the device lifetime. By increasing the thickness of an Al cathode that is in contact with the moisture getter, we have obtained much enhanced thermal and barrier properties. Namely, the maximum surface temperature is reduced by 30.5 °C (from 62.4 to 31.9 °C) and the operating lifetime is comparable with that of the conventional glass-encapsulated OLED.

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► Thermal and barrier properties of moisture getter-filled encapsulations for OLEDs.
► The getter-coated flat glass encapsulation dissipated heat by 27.7 °C.
► But, it exhibited the poorest gas diffusion barrier property.
► Its barrier property was much enhanced by increasing the thickness of the Al cathode.
► It also brought in a further reduction (by 30.5 °C) of the surface temperature.