Enhanced light extraction from organic light emitting diodes by micrometer-sized buckles

Area of Science:

• Materials Science
• Optoelectronics
• Nanotechnology

Background:

• Enhancing light extraction is crucial for improving organic light-emitting diode (OLED) efficiency.
• Surface texturing of transparent conductive oxides (TCOs) is a common approach to improve light extraction.

Purpose of the Study:

• To investigate simple methods for creating buckled structures to enhance light extraction in OLED devices.
• To explore the effect of buckling instability in indium tin oxide (ITO) layers on OLED performance.

Main Methods:

• Indium tin oxide (ITO) was deposited on polymer-coated glass using sputtering.
• Buckling instability was induced by controlling argon gas pressure during ITO deposition.
• Atomic force microscopy (AFM) was used to characterize the buckled ITO surface.
• Fabrication of OLED devices using buckled ITO anodes.

Main Results:

• Buckling instability in ITO films was observed, creating micron-sized textured structures.
• The buckling process was controllable by adjusting argon gas pressure during sputtering.
• OLEDs fabricated with buckled ITO anodes showed reduced operating voltage.
• A 5% increase in current efficiency and a 44% increase in power efficiency were observed in OLEDs with buckled ITO.
• Broader light distribution was achieved, as indicated by angular light intensity measurements.

Conclusions:

• Buckled ITO structures offer a simple and effective method for enhancing light extraction in OLEDs.
• This technique leads to significant improvements in OLED efficiency and light distribution.
• Controlling sputtering parameters provides a viable route to engineer surface morphology for optoelectronic applications.