Marta Llusca Jane's research while affiliated with University of South Australia and other places

Smart materials that are energy efficient and take up less space are crucial in the development of new technologies. Electrochromic polymers (ECPs) are one such class of materials that actively change their optical behavior in both visible and infrared parts of the electromagnetic spectrum. They show promise in a wide range of applications, from active camouflage to smart displays/windows. The full capabilities of ECPs are still yet to be explored, for while their electrochromic properties are well established, their IR modulation is less reported on. This study addresses the potential of ECPs in active IR modulating devices by optimization of Vapor Phase Polymerized poly(3,4-ethylenedioxythiophene) (PEDOT) thin films via the substitution of its dopant anion. Dynamic ranges denoting emissivity changes between reduced and oxidized states of PEDOT were found across dopants of tosylate, bromide, sulfate, chloride, perchlorate and nitrate. Relative to the emissivity of reduced (neutral) PEDOT, a range of ±15% was achieved from the doped PEDOT films, and a maximum dynamic range of 0.11 across a 34% change was recorded for PEDOT doped with perchlorate. This article is protected by copyright. All rights reserved.

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.

The commercial building and residential sectors are responsible for 27% of the global electricity consumption, with cooling and heating loads being the dominant contributors. Much of the thermal energy inside of buildings is wasted by means of transmission through conventional windows. Low emissivity (low-e) windows have been incorporated as an effective method to minimize energy utilisation because of their ability to reflect external heat radiation, thus reducing cooling loads. Such windows have been widely used in the architectural and automotive sectors to block both ultraviolet (UV) and infrared (IR) radiation from the Sun. The windows consist of multi-layer thin coatings (metallic and dielectric layers), which are highly transparent in the visible but reflective to IR radiation (heat). However, the metallic layers attenuate telecommunication signals used for modern-day telecommunications such as radio frequency (RF) and microwave (μW) signals. As there is an ever-increasing demand for a reliable interior to exterior mobile communication coverage, these windows need to be transparent for reliable wireless communication. A class of engineered materials is a promising solution to improve signal transmission through low-e windows; by applying a frequency selective surface (FSS) pattern onto the window. FSS can be realised by producing a periodic of repetitive shapes incorporated onto the window surface to filter selective electromagnetic waves. This review highlights the FSS patterning technique applied onto low-e windows to allow for low attenuation transmission of telecommunication signals.

Low emissivity (low-e) coatings minimise heat transmittance through the coating and emission of infrared light from hot surfaces. They are used in space applications to reduce overheating of the spacecraft, in architectural applications and automotive windows to block heat from entering a building or vehicle. Typically, in window applications the low-e coatings consist of a multilayer coating, which combine metallic films (approx. 10 nm); responsible for the heat reflection and dielectric films (approx. 40 nm); used to protect the metallic films and enhance their visible transmittance. Commercially available low-e coatings can contain more than 15 layers, with Ag typically used as the metallic layer. However, Ag is soft and tends to tarnish, making Ag-based low-e coatings vulnerable to degradation when exposed to environmental conditions. In this study we demonstrated environmentally durable low-e coatings based on Ag–Cu alloyed thin films. The thin film alloys showed higher level of scratch resistance than conventional pure Ag coatings with high level of transmittance of visible light. The multilayer coating consisting of a dielectric film, metal alloy film and a protective coating was demonstrated as robust, long-life, first surface low-e coating.