Simulations of sinusoidal nanotextures for coupling light into c-Si thin-film solar cells

Abstract

We numerically study coupling of light into silicon (Si) on glass using different square and hexagonal sinusoidal nanotextures. After describing sinusoidal nanotextures mathematically, we investigate how their design affects coupling of light into Si using a rigorous solver of Maxwell's equations. We discuss nanotextures with periods between 350 nm and 1050 nm and aspect ratios up to 0.5. The maximally observed gain in the maximal achievable photocurrent density coupled into the Si absorber is 7.0 mA/cm² and 3.6 mA/cm² for a layer stack without and with additional antireflective silicon nitride layers, respectively. A promising application is the use as smooth anti-reflective coatings in liquid-phase crystallized Si thin-film solar cells.

On accurate simulations of thin-film solar cells with a thick glass superstrate

“…Figure 2 shows 1 − R 1 and 1 − R 0 for the layer stack sketched in Fig. 1(a) for a negative cosine texture that forms the interface between sol-gel and the silicon absorber [1]. Indeed, large differences are seen between R 1 and R 0 .…”

“…The results are presented for the negative cosine "−cos" geometry introduced in Ref. [1] with P = 750 nm period and an aspect ratio of 0.5 (structure height 375 nm), which is illustrated on the right hand side. The differences between the two corrections are because of diffraction orders that are present in glass but cannot propagate into air [see Fig.…”

“…Because of this perfect periodicity, the far-field reflection and transmission into the top and bottom infinite half spaces, which cover the layer stack, only happens into discrete and well-defined channels [1]. The reflectivity R of the structure in the glass halfspace can be calculated with…”

“…1. (a) A cross section through a periodical unit cell with a sinusoidal interface [1] and the glass and silicon half spaces. The first-order correction described in this paper is performed for the propagation of light from glass into air.…”

On Accurate Simulations of Thin-Film Solar Cells With a Thick Glass Superstrate

“…where the superscript 0 denotes the zeroth order correction, R g is the reflectivity of the air-glass interface (about 4% at normal incidence) and λ is the wavelength [1,2].…”