Low-Haze Microlens Arrays with Nano-Pores Fabricated with PMMA Particles for Flexible Polymer Light-Emitting Diodes

Abstract

In this paper, we describe low-haze microlens arrays with a porous morphology. The microlens arrays were fabricated by a simple soft lithographic technique, which is basically the transfer of a pattern made by the self-assembly of polystyrene particles, to a thermally-curable silica hybrid sol on flexible substrate using a poly(dimethylsiloxane) replica mold. The poly(methyl methacrylate) (PMMA) particles were synthesized and mixed with the silica sol. Moderate intensity oxygen plasma etching was used to form a porous morphology on the surface of microlens array, by etching the PMMA particles incorporated in the silica sol. The density of pores was controlled by varying the concentration of the PMMA particles. As a result, the haze value was reduced from 62% to 50%. In addition, flexible blue polymer light-emitting diodes attached to the microlens array with nano-pores exhibited 27% enhanced current efficiency. From these results, it is concluded that the microlens array with nanopores can be an efficient optical structure for future flexible displays to extract light from the substrate modes with reduced haze.