Analysis by finite element calculations of light scattering in laser-textured AZO films for PV thin-film solar cells

In the thin-film photovoltaic industry, to achieve a high light scattering in one or more of the cell interfaces is one of the strategies that allow an enhancement of light absorption inside the cell and, therefore, a better device behavior and efficiency. Although chemical etching is the standard method to texture surfaces for that scattering improvement, laser light has shown as a new way for texturizing different materials, maintaining a good control of the final topography with a unique, clean, and quite precise process. In this work AZO films with different texture parameters are fabricated. The typical parameters used to characterize them, as the root mean square roughness or the haze factor, are discussed and, for deeper understanding of the scattering mechanisms, the light behavior in the films is simulated using a finite element method code. This method gives information about the light intensity in each point of the system, allowing the precise characterization of the scattering behavior near the film surface, and it can be used as well to calculate a simulated haze factor that can be compared with experimental measurements. A discussion of the validation of the numerical code, based in a comprehensive comparison with experimental data is included

Microstructure FSS patterning to improve 5G microwave signals through low-e plastic windows

Low emissivity (low-e) windows are widely used in the architectural sector to block the infrared (IR) radiation from the Sun. The windows contain a multilayer nanoscale coating of metallic and dielectric layers. The metallic layer, which is responsible for the IR reflection, also attenuates the radio and microwave frequencies used for modern-day technologies such as Fifth Generation (5G) communications. As there is an ever-increasing demand for a reliable interior-to-exterior signal coverage, low-e windows should be transparent to such signals. A class of surface modification — Frequency Selective Surface (FSS) is the technique of choice to be applied on the thin metallic coating to transmit the wireless signal.In this work, a thin silver (Ag) film — 10 nm thick was deposited by electron beam evaporation on polycarbonate substrates as an example low-e coating. Despite excellent IR blocking (64 %) and visible light transmittance (60 %), it also presented a high attenuation of 20 dB at 5G signal bands (72–82 GHz).​ FSS patterns of various geometries and sizes were applied via laser ablation and evaluated to provide the lowest attenuation. We demonstrated that the application of the hexagonal pattern provided largest improvement reducing the 5G attenuation value from 20 dB to 1 dB, without compromising the visible transmittance and having only a minor effect on IR reflection