A conceptual model of light coupling by pillar diffraction gratings

Abstract

Diffractive structures such as pillar gratings are a promising way of coupling light into or out of thin semiconductor devices, for applications in thin film solar cells and light-emitting diodes. In this paper we show that the diffuse transmittance behavior of pillar gratings can be understood using the concept of grating mode interference and that the optimum heights of the grating and an estimate of the optimum period can be predicted with the effective index method. Furthermore, the method also gives good results for structures outside the range for which it was derived, including circular pillars and quasiperiodic structures. We also show that pillar gratings offer substantially improved performance over groove gratings for thin film silicon solar cells.

Optical absorption enhancement in a hybrid system photonic crystal — Thin film for photovoltaic applications

“…We attribute such rise in the absorption to the coupling of PC quasi-guided modes and the incident light. This effect has been observed before in PC [4,8,17] and it is very useful when using hybrid systems (PC+substrate) like the ones described here. …”

Efficiency of thin-films silicon solar cells with a photonic pattern

“…[5][6][7]), and it has become a hot topic in the last few years (Refs. [8][9][10][11][12][13][14][15][16][17][18][19][20][21]). The structures analyzed in the literature span from very idealized to realistic ones, namely, from bare photonic crystal slabs (Refs.…”

Optical response from lenslike semiconductor nipple arrays

“…The latter reflects a subtlety of gradual index matching inherent in a tapering distribution of refractive index n͑z͒ in the depth ͑z͒ direction. 6,7 These observations inspire a strategic study to enhance the solar cell efficiency by taking advantage of the biomimetic antireflection effect 8 and the increase in optical absorption length due to structure-related high-order forward diffractions. 9 Indeed submicron pyramidal gratings 9 and pillars with a cone-shape etch top 8,10 are two popular surface textures that have been proposed to mimic the antireflection function of lenslike nipple array.…”