Abstract

Electrochromic films have been used as a non-emissive material for display applications. Such materials have already been integrated in antiglare rearview mirrors for passenger vehicles as well as smart windows intended for energy savings for buildings. However, most electrochromic materials are deposited on rigid substrates, which prevent its use in flexible and stretchable electronic applications, where low temperature deposition techniques are desired. Additionally, electrochormics require an external power source to drive the underlying reduction/oxidation reaction. In this work, electrochromic materials inkjet-printed onto flexible and stretchable substrates have been explored. These devices are 'self-powered' by organic solar cells also fabricated on flexible and stretchable substrate such as PDMS and PET. A set of inks based on a combination of synthesized and commercially obtained WO-3 nanoparticles, W-TiO-2 and TiO-2 nanoparticles were evaluated. The microstructure of the nanoparticles used in this study were examined under scanning electron microscopy for examining nanoparticle morphology, x-ray diffraction for chemical and structural characterization, and dynamic light scattering for particle size determination. Electrochromic layers were then ink-jet printed on flexible and stretchable PDMS substrates, using synthesized Ag nanowires as conductive, yet highly transparent electrodes. The stretchable printed electrochromic devices under various stress conditions and electrochromic performances were evaluated and demonstrated clear switching behavior under external bias, with 7 second coloration time, 8 second bleaching time, and 0.36-0.75 optical modulation at ?=525 nm. Cyclic voltammetry and galvanostatic charge/discharge measurements demonstrated high areal capacitance, with limited stability upon cycled operation. The electrochromic devices were then integrated in an Internet of Things (IoT)-enabled switching configuration, self-powered by PCDTBT:PC-70BM organic photovoltaics. The bulk heterojunction devices were evaluated with varying hole-transport layers and substrates, and exhibited the strongest performance of PCE? 3%, V-oc=0.9V and J-sc ? 10-15 mA/cm^2. The described self-powered, IoT-enabled, ink-jet printed electrochromic devices, fabricated on flexible substrates, are demonstrative of potential applications for wearable electronics.

Original languageEnglish (US)
Title of host publicationProceedings - IEEE 68th Electronic Components and Technology Conference, ECTC 2018
PublisherInstitute of Electrical and Electronics Engineers Inc.
Pages131-138
Number of pages8
Volume2018-May
ISBN (Print)9781538649985
DOIs
StatePublished - Aug 7 2018
Event68th IEEE Electronic Components and Technology Conference, ECTC 2018 - San Diego, United States
Duration: May 29 2018Jun 1 2018

Other

Other68th IEEE Electronic Components and Technology Conference, ECTC 2018
CountryUnited States
CitySan Diego
Period5/29/186/1/18

Keywords

  • Electrochromic
  • Internet of Things self-powered smart window
  • Photovoltaic
  • Wearable electronics

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Electrical and Electronic Engineering

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  • Cite this

    Azhar, E. A., Alford, T., & Yu, H. (2018). Self-Powered, Inkjet Printed Electrochromic Films on Flexible and Stretchable Substrate for Wearable Electronics Applications. In Proceedings - IEEE 68th Electronic Components and Technology Conference, ECTC 2018 (Vol. 2018-May, pp. 131-138). [8429541] Institute of Electrical and Electronics Engineers Inc.. https://doi.org/10.1109/ECTC.2018.00028