Sustainable Dual-Mode Smart Windows for Energy-Efficient Buildings

Sílvia C. Nunes, Sofia M. Saraiva, Rui F. P. Pereira, Sónia Pereira, Maria Manuela Silva, Luís D. Carlos, Elvira Fortunato, Rute A. S. Ferreira, Rosa Rego, Verónica de Zea Bermudez

Research output: Contribution to journalArticlepeer-review

28 Citations (Scopus)


Electrochromic devices (ECDs) combining visible/near-infrared (NIR) transparent amorphous indium zinc oxide (a-IZO) external layers with innovative NIR-emitting electrolytes composed of red seaweed-derived κ-carrageenan (κ-Cg) polysaccharide, glycerol (Gly), and erbium triflate (ErTrif 3 ·xH 2 O) are proposed as a valuable technological solution for the development of smart windows providing less heating demand, less glare and more indoors human comfort for the new generation of energy-efficient buildings. The electrolyte preparation is cheap, clean, and fast. The optimized sample including 50 wt% Gly/κ-Cg and 40 wt% ErTrif 3 ·xH 2 O/κ-Cg exhibits the highest ionic conductivity (1.5 × 10 -4 S cm -1 at 20 °C) and displays ultraviolet (UV)/blue and NIR emissions associated with the κ-Cg-based host and the Er 3+ ions ( 4 I 15/24 I 13/2 ), respectively. The 5-layer configuration ECD tested demonstrated fast switching time (50 s), high electrochromic contrast (transmittance variations of 46/51% at 550/1000 nm), high optical density change (0.89/0.75 at 550/1000 nm), outstanding coloration efficiency (450th cycle = -15902/-13400 cm 2 C -1 and +3072/+2589 cm 2 C -1 at 550/1000 nm for coloration and bleaching, respectively), excellent electrochemical stability, and self-healing after mechanical damage. The ECD encompasses two voltage-operated modes: semibright warm (+3.0 V, transmittances of 52/61% at 550/1000 nm) and dark cold (-3.0 V, transmittances of 7/11% at 550/1000 nm).

Original languageEnglish
Pages (from-to)1951-1960
Number of pages10
JournalACS Applied Energy Materials
Issue number3
Publication statusPublished - 25 Mar 2019


  • energy-efficient glazing for buildings
  • erbium triflate
  • glare reduction
  • heating saving
  • NIR-emitting smart windows
  • window daylighting control
  • κ-carrageenan polysaccharide


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