Flexible Organic Light-emitting Diode - Disadvantages

Disadvantages

Both the flexible substrate itself as well as the process of bending the device introduce stress into the materials. There may be residual stress from the deposition of layers onto a flexible substrate,, thermal stresses due to the different coefficient of thermal expansion of materials in the device, in addition to the external stress from the bending of the device.

Stress introduced into the organic layers may lower the efficiency or brightness of the device as it is deformed, or cause complete breakdown of the device altogether. Indium tin oxide (ITO), the material most commonly used as the transparent anode, is brittle. Fracture of the anode can occur which can increase the sheet resistance of the ITO or disrupt the layered structure of the OLED. Although ITO is the most common and best understood anode material used in OLEDs, research has been undertaken into alternative materials that are better suited for flexible applications including carbon nanotubes.

Encapsulation is another challenge for flexible OLED devices. While the common method of encapsulation for regular OLEDs is to seal the organic layer between glass, this is inappropriate for flexible OLEDs. The materials in an OLED are sensitive to air and moisture which lead to degradation of the materials themselves as well as quenching of excited states within the molecule. Flexible encapsulation methods are generally not as effective a barrier to air and moisture as glass, and current research aims to improve the encapsulation of flexible organic light emitting diodes.