Light management is a key issue for highly efficient liquid-phase crystallized silicon (LPC-Si) thin-film solar cells and can be achieved with periodic nanotextures. They are fabricated with nanoimprint lithography and situated between the glass superstrate and the silicon absorber. To combine excellent optical performance and LPC-Si material quality leading to open circuit voltages exceeding 640 mV, the nanotextures must be smooth. Optical simulations of these solar cells can be performed with the finite element method (FEM). Accurately simulating the optics of such layer stacks requires not only to consider the nanotextured glass-silicon interface, but also to adequately account for the air-glass interface on top of this stack. When using rigorous Maxwell solvers like the finite element method (FEM), the air-glass interface has to be taken into account a posteriori, because the solar cells are prepared on thick glass superstrates, in which light is to be treated incoherently. In this contribution we discuss two different incoherent a posteriori corrections, which we test for nanotextures between glass and silicon. A comparison with experimental data reveals that a first-order correction can predict the measured reflectivity of the samples much better than an often-applied zeroth-order correction.
Proc. SPIE. 9898, Photonics for Solar Energy Systems VI
KEYWORDS: Thin films, Refractive index, Antireflective coatings, Polarization, Solar cells, Interfaces, Silicon, Numerical simulations, Thin film solar cells, Thin film solar cells, Finite element methods, Diffraction gratings, Absorption, Maxwell's equations
Hexagonal sinusoidal nanotextures are well suited to couple light into silicon on glass at normal incidence, as we have shown in an earlier publication [K. Jäger et al., Opt. Express 24, A569 (2016)]. In this manuscript we discuss how these nanotextures perform under oblique incidence illumination. For this numerical study we use a rigorous solver for the Maxwell equations. We discuss nanotextures with periods between 350 nm and 730 nm and an aspect ratio of 0.5.
Thin-film solar cells contain nano-textured interfaces that scatter the incident light, leading to increased absorption and hence increased current densities in the solar cell. In this manuscript we systematically study optimized random nano-textured morphologies for three different cases: amorphous hydrogenated silicon solar cells (a-Si:H, bandgap 1.7 eV), nano-crystalline silicon solar cells (nc-Si:H, bandgap 1.1 eV) and tandem solar cells consisting of an a-Si:H and a nc-Si:H junction. For the optimization we use the Perlin texture algorithm, the scalar scattering theory, and a semi-coherent optical device simulator.
The scattering properties of transparent conductive oxide (TCO) layers are fundamentally related to the performance of
thin film silicon solar cells. In this study we introduce an experimental technique to access light scattering properties at
textured TCO-silicon interfaces. Therefore we prepared a sample with a polished microcrystalline silicon layer, which is
deposited onto a rough TCO layer. We used the measured results to validate calculations obtained with rigorous diffraction
theory, i.e. a numerical solution of Maxwell's equations. Furthermore we evaluated four approximate models based on the
scalar scattering theory and ray tracing and compared them to the rigorous diffraction theory.
Conference Committee Involvement (1)
Nanostructured Thin Films XI
19 August 2018 | San Diego, California, United States