General displays such as liquid crystal displays (LCDs) and organic electroluminescent displays (OELDs) are equipped in most of the electronic devices we use in our everyday life. In addition, there are increase in demand for displays that can present information in a variety of forms such as wearable displays. However, it is impossible to cut these displays into various shapes because it is necessary to seal the contents of both LCDs and OELDs, for example, as the LCDs contain liquid and OELDs are susceptible to water, oxygen and other impurities. Moreover, since these displays require continuous power supply to maintain their functions, they must be always connected with a power source. Due to these requirements, it had been hard to develop cuttable displays using existing technologies.
In this presentation, I introduce new display sheets that can be cut into any shape with scissors, using metallo-supramolecular polymers with electrochromic (EC) properties . Fe(II)-based metallo-supramolecular polymer was synthesized by 1:1 complexation of Fe(II) diacetate with bis(terpyridyl)benzene. The polymer is soluble in polar solvents such as methanol and was sprayed onto a flexible ITO plastic substrate to form a coating layer stable against moisture and oxygen. Another flexible ITO substrate was covered with a solid-state electrolyte including lithium perchlorate as an electrolyte. The display sheet was fabricated by lapping the EC polymer-coated substrate and the electrolyte-covered substrate. In the obtained display device, the blue color of polymer layer disappeared electrochemically when a voltage (3 V) was applied between the two ITO electrodes. This electrochromic behavior is based on the redox between Fe(II) and Fe(III). The metal-to-ligand charge transfer (MLCT) absorption from Fe(II) to the organic ligand exists in the polymer, but the absorption disappears by the oxidation of Fe(II) to Fe(III). The display requires only a few seconds of electrical input to switch visual information, and the display will last even after power supply is discontinued. Accordingly, we successfully developed a sheet type display device capable of functioning while being detached from a power source and after being cut into a shape.
We propose a concept called “new life style in which people can enjoy changeable colors in everything.” We envision the application of the new technology in society whereby people can freely change the colors of various objects/items, e.g. windows, the interior or exterior of motor vehicles and buildings, umbrellas and sunglasses.
This study was partially conducted under the project “ultrafast, ultralow-power, ultralarge-area electrochromism” in the CREST project, Japan Science and Technology Agency (JST).
M. Higuchi et al., Chem. Rec., 7, 203 (2007); Adv. Mater., 19, 3928 (2007); J. Am. Chem. Soc., 130, 2073 (2008); J. Am. Chem. Soc., 133, 1168 (2011); Chem. Asian J., 8, 76 (2013); J. Mater. Chem. C, 1, 3408 (2013); Eur. J. Inorg. Chem., 2014, 3763 (2014); ACS Appl. Mater. Interfaces, 6, 9118 (2014); J. Mater. Chem. C, 2, 9331 (2014); ACS Appl. Mater. Interfaces, 7, 18266 (2015); ACS Appl. Mater. Interfaces, 7, 25069 (2015); J. Mater. Chem. C, 4, 9428 (2016).
Hosted By: Professor John Reynolds, Dr. Anna Osterholm, and Dr. Eric Shen