Controlling bucking structure by UV/ozone treatment for light extraction from organic light emitting diodes

We describe a simple and effective method to control the periodicity of the buckling structure by thermal evaporation and ultraviolet/ozone (UVO) treatment so as to effectively extract the waveguide modes in organic light emitting diode (OLED) devices, inferring an underlying buckling mechanism. The periodicity of the buckles decreased from 460 to 300 nm with the UVO treatment time, shifting the emission wavelength showing the highest enhancement ratio toward the shorter wavelengths in the device with buckles. We exemplified the outcoupling characteristics of the waveguide modes by the buckles with different periodicities.