Diffractive light-trapping transparent electrodes using zero-order suppression

Abstract

A light-trapping transparent electrode design based on sub-surface binary dielectric gratings is introduced and demonstrated experimentally. The structure consists of metallic wires patterned with an array of silicon nanobeams. Optimization of the grating geometry achieves selective suppression of zero-order diffraction, while enabling redirection of incident light to an angle that exceeds critical angle of the local environment. Subsequent total-internal reflection allows recovery of light initially incident on the patterned metal wire. Experiments involving amorphous silicon gratings patterned on gold wires demonstrate a light-trapping efficiency exceeding 41 %. Modeling of crystalline silicon nanobeams on silver wires suggests that a shadowing loss reduction of 82 % is feasible. The achievement of a large shadowing reduction using a coplanar structure with high manufacturing tolerance and a polarization-insensitive optical response makes this design a promising candidate for integration in a wide range of real-world photonic devices.

Keywords

• binary diffractive gratings
• light trapping
• nanofabrication
• transparent electrodes