These organic light emitting diodes (OLEDs) feature a unique metal buckling structure that enhances light output and power efficiency without blurring images. The market for OLEDs as lighting (a subset of the large OLED market) is expected to reach $3 billion in 2015. Available OLEDs suffer from low power efficiency because some of the light generated by the input current is internally reflected and trapped in the OLED itself. Light trapping is caused by refractive index mismatches between air, glass substrate, and the electrode layer within a light cell. In order to address the light trapping, researchers at the University of Florida have developed a buckling structure that increases the effective light production of an OLED by permitting more light to escape. The buckle itself mitigates the effect of refractive index mismatch by interrupting and curving the layers of an OLED. This buckled structure forms the OLED, which displays improved light output without increased blur.
A waveguide is a structure that guides different types of waves, in this case, light waves. The buckling structure is used as a grating to extract the waveguiding modes in OLEDs, which aids in recovery of light, thus increasing efficiency. The buckling structure is formed by spincoating a glass substrate covered with polydimethylsiloxane (PDMS) layer, thermally evaporating aluminum from the PDMS layer and cooling it. The difference in the temperature between the evaporated aluminum and the PDMS induces a stress that forms the structure. This formation process aids the OLED in improved light output relative to flat OLED devices, as well as in omitting blur-free light.
