Flexible Transparent Heater Fabricated from Spray-Coated In:ZnO/Ag-NWs/In:ZnO Multilayers on Polyimide Foil.

Rachmat Adhi Wibowo,Stefan Edinger,Neha Bansal,Katharina Rauchenwald,Theodoros Dimopoulos,Stefan Diebald,Daniel Habenbacher

doi:10.3390/nano12030316

Rachmat Adhi Wibowo, Stefan Edinger + Show 5 more

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https://doi.org/10.3390/nano12030316

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Abstract

A flexible transparent heater is presented, based on an all-sprayed composite architecture of indium-doped zinc oxide (IZO) layers that sandwich a network of silver nanowires, on a polyimide-foil substrate. This architecture could be materialized through the development of a low-temperature (240 °C) spray-pyrolysis process for the IZO layers, which is compatible with the thermal stability of the transparent polyimide substrate and allows for the formation of compact and transparent layers, without precipitates. The IZO layers entirely embed the silver nanowires, offering protection against environmental degradation and decreasing the junction resistance of the nanowire network. The resulting transparent heaters have a high mean transmittance of 0.76 (including the substrate) and sheet resistance of 7.5 Ω/sq. A steady-state temperature of ~130 °C is achieved at an applied bias of 3.5 V, with fast heater response times, with a time constant of ~4 s The heater is mechanically stable, reaching or surpassing 100 °C (at 3.5 V), under tensile, respectively, compressive-bending stress. This work shows that high-performance transparent heaters can be fabricated using all-sprayed oxide/silver-nanowire composite coatings, that are compatible with large-scale and low-cost production.

Highlights

Flexible transparent heaters of indium-doped zinc oxide (IZO)/Ag-NWs/IZO were deposited on 50 μm-thick, transparent polymide (PI) substrates (Yangzhou Guotai Fiberglass Co., Yangzhou, China), by sequential spray deposition of (a) bottom IZO layer, (b) Ag-NWs and (c) top IZO layer, using a Sono-Tek, ExactaCoat® (Sono-Tek, Milton, NY, USA) coating system, equipped with a 120 kHz Impact® ultrasonic nozzle, in horizontal geometry
Layer is employed for multiple reasons, namely, (a) it can act as a diffusion barrier between the substrate and the Ag-NWs during the TH deposition and operation, (b) it improves the substrate wettability in the case where techniques such as rod-coating, spin-coating or doctor-blading are used for the Ag-NWs deposition, (c) it improves the NW junction resistance, as it has reproducibly led to lower sheet resistance values, as compared to the case where only the top IZO layer was used
The nanocrystalline nature of the IZO layer is a consequence of its deposition at the reduced temperature of 240 ◦ C, which is the lowest reported in the literature

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Transparent conducting materials (TCMs) combine high visible transparency with high-electrical conductivity. They are applied across a vast number of applications, comprising optoelectronic devices (such as light-emitting diodes, thin-film displays and touchscreens), photovoltaic modules, sensors and actuators, low-emissivity and electrochromic window coatings, etc. Transparent conducting oxides (TCOs), which in their majority are highly doped, n-type semiconductors, have the widest implementation among TCMs [2]

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