On-Surface Self-Assembly of Stimuli-Responsive Metallo-Organic Films: Automated Ultrasonic Spray-Coating and Electrochromic Devices

Naveen Malik, Neta Elool Dov, Graham De Ruiter, Michal Lahav, Milko E. Van Der Boom

Research output: Contribution to journalArticlepeer-review

17 Citations (Scopus)


We demonstrate the on-surface formation of homogeneous and uniform electrochromic films via ultrasonic spray coating. This fully automated process is capable of fabricating metallo-organic films on transparent conducting oxides (TCOs) on glass or flexible poly(ethylene terephthalate) (PET) with surface areas of up to 36 cm2 and film thicknesses of half a micron. The assembly process involves alternatingly spray-coating dilute solutions of structurally well-defined iron polypyridyl ([Fe(mbpy-py)3]2+) complexes and bis(benzonitrile)palladium dichloride (Pd(PhCN)2Cl2) onto conductive substrates, where the latter palladium salt was used as the inorganic cross-linker. The on-surface self-assembled three-dimensional networks are intensely colored and were subsequently integrated into laminated electrochromic devices (ECDs) containing a lithium-based gel electrolyte. The ECDs retain their intense color in the ground state, having a ΔTmax of 40-49% at λmax ≈ 600 nm, and can be operated for up to 1500 redox cycles. The fluorine-doped tin oxide counter electrode coated with poly(3,4-ethylene-dioxythiophene)polystyrene sulfonate (PEDOT:PSS) as a charge-storage layer resulted in these stable devices. A significant decrease in the potential window of ΔE ≈ 2.5 V was achieved by using a metal grid on PET as the counter electrode. The operation of the electrochromic films is diffusion-controlled, and the diffusion coefficients (Df) reflect their molecular densities. During these studies, we found that ClO4- is a suitable counterion of the lithium-based electrolytes for optimal ECD performance.

Original languageEnglish
Pages (from-to)22858-22868
Number of pages11
JournalACS Applied Materials and Interfaces
Issue number25
Publication statusPublished - Jun 26 2019


  • coordination chemistry
  • electrochromic devices
  • electrochromics
  • metallo-organics
  • self-assembly
  • spray-coating
  • thin films

ASJC Scopus subject areas

  • Materials Science(all)

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