Enhanced Light Outcoupling Efficiency in Organic Light-Emitting Devices Using Irregular Microlenses Fabricated with 3D Colloidal Arrays

Abstract

For the purpose of achieving high luminance, the introduction of microlenses could be a useful technique to enhance the light outcoupling efficiency because it can be easily applied to all types of lightings. However, the prevalent microlens arrays have been generally fabricated by expensive and complicated photo-lithographic methods and have periodic structures, leading to variations of the emission spectrum in organic light-emitting devices (OLEDs). In this study, we demonstrate a facile and economic fabrication method that can be used for irregular microlens arrays with high fill factors. The fill factors of microlens arrays were measured to be about 90%. The irregular microlens arrays can be easily fabricated by a soft-lithographic technique with replica molds prepared from three-dimensional (3D) polymeric colloidal arrays as master molds. Compared to conventional devices, OLEDs with irregular microlens arrays have showed an enhancement of 40% in light outcoupling efficiency and maintained the original spectra by suppressing the interference effect.