Molecular Engineering of High-Performance Electrochromic Nanolayers

Rensselaer Polytechnic Institute, Troy NY

Investigators

Abstract

Professor Peter H. Dinolfo of the Department of Chemistry and Chemical Biology at Rensselaer Polytechnic Institute is supported by the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry to develop a new type of electrochromic materials. Electrochromic materials change color when electricity is applied. The materials in this project are composed of thin film coatings of transition metal (mainly cobalt) complexes on solid surfaces. The project reveals fundamental chemical knowledge to better understand the how and why color changes occur. The knowledge obtained is critical to improving smart windows (improving building energy efficiency), antiglare coatings for automobile mirrors, chemical sensors, display materials, and optical memory devices. While many classes of electrochromic materials are available, the project promises to develop materials that maintain their color in a given chemical state after the electrical signal is switched off. As a result, this new class of materials is expected to have the advantage of operating with less electrical energy consumption. During the course of conducting this research, graduate and undergraduate students are trained in synthesis, material preparation and characterization and device construction. In addition, solar chemistry camps are organized and made available for high school students under the Summer at Rensselaer High School Research program. The project addresses the increasing need for electrochromic materials with high color contrast between states, coloration efficiency, long-term cycling durability and fast switching speeds. The focus is on the development of a new class of electrochromic materials using redox coupled spin crossover (RCSCO) organometallic complexes. Such materials undergo chemical transformations upon oxidation or reduction with significant splitting of the anodic and cathodic waves for a given redox couple. Click chemistry via a layer by layer method is used to generate nanoscale thin film electrochromic materials using cobalt (Co) complexes as building blocks. The resulting electrochromic materials are subjected to a series of experiments to investigate the effects of ligand binding to the Co centers on their spectroscopic, electrochemical, and magnetic properties. The team also examines the electrochemical charge transfer rates through their multilayer assemblies and investigates their coloration efficiency, switching times, and cycle lifetimes. The results inform the systematic variation of the molecular structure to optimize the material for specific electrochromic applications. Success of this research may transform how studies of transition metal coordination compounds featuring redox-coupled spin-crossover compounds are used as building blocks in electrochromic devices. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.