Layer-by-Layer Approach to (2+1)D Photonic Crystal Superlattice with Enhanced Crystalline Integrity

Abstract

Large-area polystyrene (PS) colloidal monolayers with high mechanical strength are created by a combination of the air/water interface self-assembly and the solvent vapor annealing technique. Layer-by-layer (LBL) stacking of these colloidal monolayers leads to the formation of (2+1)D photonic crystal superlattice with enhanced crystalline integrity. By manipulating the diameter of PS spheres and the repetition period of the colloidal monolayers, flexible control in structure and stop band position of the (2+1)D photonic crystal superlattice has been realized, which may afford new opportunities for engineering photonic bandgap materials. Furthermore, an enhancement of 97.3% on light output power of a GaN-based light emitting diode is demonstrated when such a (2+1)D photonic crystal superlattice employed as a back reflector. The performance enhancement is attributed to the photonic bandgap enhancement and good angle-independence of the (2+1)D photonic crystal superlattice.

Keywords: LEDs; colloidal monolayers; light extraction efficiency; photonic crystal superlattices; self-assembly; superlattices.