Fabrication of an anodized nanoporous aluminium (AAO/Al) transparent electrode as an ITO alternative for PDLC smart windows

Abstract

The expensive tin-doped indium oxide (ITO) layer employed as the transparent conducting electrode (TCE) prevents the widespread application of contemporary liquid crystal (LC) smart window technologies in the consumer market. In this niche, the present work describes the fabrication of an affordable PDLC smart window device using a cost-effective TCE namely, anodized nanoporous aluminium (AAO/Al) developed through facile anodization of thin Al film deposited on a transparent substrate. A high-performing TCE is achieved by optimising a range of processing parameters, including anodization voltage, time, and chemical etching. The developed AAO/Al TCE exhibits a good optoelectronic property with visible transmittance (T) of ∼70%, and sheet resistance (R_sh) of ∼128 Ω □⁻¹, along with excellent electrochemical stability, and robustness in extreme environmental conditions (temp. > 300 °C). Most importantly, the TCE possesses anti-reflection characteristics attributed to the porous nanostructures of the anodized film. For entrenching the commercial viability, a polymer dispersed liquid crystal (PDLC) smart window of dimension 3 × 2 cm² was devised utilizing the TCE. Intriguingly, the device needs only a 30 V operating voltage to attain a high switching contrast of 45%. Therefore, the TCE developed in this work can be an exceptional replacement for conventional ITO in fabricating affordable PDLC smart windows.