OLED stretches two-dimensionally on strain relief substrate

Technology News |
By eeNews Europe

The stress-relief substrate features a unique structure with pillar arrays to reduce the stress on the active areas of devices when strain is applied. Their stretchable OLED prototypes presented in a Nano Letters paper titled “Two-Dimensionally Stretchable Organic Light-Emitting Diode with Elastic Pillar Arrays for Stress Relief” contained an elastic substrate structure with bonded elastic pillars and bridges. The patterned upper substrate featuring the bridges makes the rigid substrate stretchable, while the pillars decentralize the stress on the device, the authors report.

Photographs of the patterned rigid part of the substrate on
the finger joint indicating 2D dimensional stretchability and
images of stretchable OLEDs on a finger joint emitting green
light. Source KAIST.

Although various applications using micro-pillar arrays have been reported, it has not yet been reported how elastic pillar arrays can affect substrates by relieving the stress applied to those substrates upon stretching, the authors note. Compared to results using similar layouts with conventional free-standing, flat substrates or island structures, their results with elastic pillar arrays show relatively low stress levels at both the bridges and plates when stretching the devices.

So far, intrinsically stretchable OLEDs have had commercial limitations due to their low efficiency in the electrodes’ electrical conductivity. Often, geometrically stretchable thin film OLEDs laminated to elastic substrates lead to varying pixel emissions from buckling and localized stress.

In this new research, the authors achieved mechanically stable stretchable RGB (red, green, blue) OLEDs patterned by thermal evaporation of an OLED stack onto the stress-relief substrate.
The bi-directional stretchability opens the way to more conformable wearable electronics and health monitoring systems.

This work was supported by the Engineering Research Center of Excellence Program supported by the National Research Foundation of Korea.


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