Development of Electrochromic Devices, Based on Polymeric Gel, for Energy Saving Applications

Carmen Rizzuto; Riccardo C Barberi; Marco Castriota

doi:10.3390/polym15163347

Development of Electrochromic Devices, Based on Polymeric Gel, for Energy Saving Applications

Polymers (Basel). 2023 Aug 9;15(16):3347. doi: 10.3390/polym15163347.

Authors

Carmen Rizzuto¹, Riccardo C Barberi^{1

2}, Marco Castriota^{1

2}

Affiliations

¹ Department of Physics, University of Calabria Ponte Bucci, Cubo 33B, 87036 Rende, CS, Italy.
² CNR-Nanotec c/o Department of Physics, University of Calabria Ponte Bucci, Cubo 33B, 87036 Rende, CS, Italy.

Abstract

In this work, the implementation of an electrochromic device (10 cm × 10 cm in size) for energy saving applications has been presented. As electrochromic system has been used with an electrochromic solution (ECsol) made by ethyl viologen diperchlorate [EV(ClO₄)₂], 1,1'-diethyl ferrocene (DEFc) and propylene carbonate (PC), as solvent. The final system has been obtained by mixing the ECsol, described above, with a polymeric system made by Bisphenol-A glycerolate (1 glycerol/phenol) diacrylate (BPA) and 2,2-Dimethoxy-2-phenylacetophenone (Irgacure 651) in a weight percentage equal to 60:40% w/w, respectively. Lithography has been used to make a spacer pattern with a thickness of about 15-20 µm between the two substrates. Micro-Raman spectroscopy confirmed the presence of the EV^•+ as justified by the blue color of the electrochromic device in the ON state. Electrochemical and optical properties of the electrochromic device have been studied. The device shows reversible electrochromic behavior as confirmed by cyclic color variation due to the reduction and oxidation process of the EV²⁺/EV^•+ couple. The electrochromic device shows a variation of the % transmittance in the visible region at 400 nm of 59.6% in the OFF state and 0.48% at 3.0 V. At 606 nm the transmittance in the bleached state is 84.58% in the OFF state and then decreases to 1.01% when it is fully colored at 3.0 V. In the NIR region at 890 nm, the device shows a transmittance of 74.3% in the OFF state and 23.7% at 3.0 V while at 1165 nm the values of the transmittance changed from 83.21% in the OFF state to 1.58% in the ON state at 3.0 V. The electrochromic device shows high values of CCR% and exhibits excellent values of CE in both visible and near-infrared regions when switched between OFF/ON states. In the NIR region at 890 nm, electrochromic devices can be used for the energy-saving of buildings with a promising CE of 120.9 cm²/C and 420.1 cm²/C at 1165 nm.

Keywords: UV-Vis-NIR and Raman spectroscopies; color contrast ratio; coloration efficiency; cyclic voltammetry; viologen.

Grants and funding

This research was partially funded by POR CALABRIA FESR-FSE 2014–2020-ASSE I—Promozione della ricerca e dell’innovazione obiettivo specifico 1.2 Azione 1.2.2′′ Project: MERAVIGLIE.