Development of electrochromic thin-film transistors on flexible substrate

• Autor(a) principal: Grey, Paul
• Data de Publicação: 2014
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/14327
• topic: Tungsten oxide (VI); Electrochromism; Electrochromic thin-film transistors; Physical vapour deposition; Thin-films; Polymer electrolytes

This work documents the fabrication and characterization of electrochromic thin-film transistors (ECTFTs) based on tungsten oxide (WO3). The ECTFTs exhibit double functionality (optical and electrical modulation) and were deposited on Corning glass and polyethylene naphthalate (PEN) by radio-frequency (RF) magnetron sputtering in an argon-oxygen atmospherewith no intentional substrate heating. The resulting amorphous WO3film connects source and drain in a planar configuration with three different architectures(conventional, interdigital and back-electrode) and isgated by a drop-casted lithium-based polymer electrolyte (LiClO4:PC). EC films were characterized using X-ray diffraction (XRD), atomic force microscopy (AFM)andopto-electrochemical measurements, the electrolyte by electrochemicalimpedance spectroscopy (EIS) and the ECTFTs by static and dynamic electrical characterization. Thinner EC films (75 nm) evidenced lower optical density (ΔOD) and color efficiency (CE) of 0,26 and 21,85 cm2C-1, respectively, but faster EC reaction kinetics, with bleaching and coloration times (tband tc) of 1,8 and 3,8 seconds, respectively. In terms of electrical properties the best performing ECTFT architecture (interdigital) showed an ION/IOFFof 2,81x105and a transconductance of 2,24 mS. The back-electrode architecturehowever showed better ionic movement control in the channel(adjustable VON)with enhanced colorations, making ita better candidate for a two-in-one (pixel + transistor) solution for display applications.