Achieving transmissive-to-black chromism via engineered dual electro-thermoresponsive single-molecule for full modulation of solar transmittance

Abstract

Pursuit of complete and null transmissive optical material in smart windows for full control of the intensity and spectrum of incoming solar light has led to the advancement of transmissive-to-black chromism. While most reported transmissive-to-black devices are electrically stimulated, we report here an alternative approach based on dual stimulation of a new dual responsive molecule. By integrating asymmetric viologen onto a newly engineered poly(2-isopropyl-2-oxazoline)-based molecule, one can achieve transmissive-to-black chromism. The synergistic effect of its thermochromic and electrochromic response when stimulated simultaneously shows full absorption of the entire visible solar spectrum resulting to a truly black state that is ideal for building facades requiring absolute privacy. Autonomous chromic switchability function is also possible by independently stimulating the material either electrically or thermally where it displays unique colored state of vibrant magenta and a hazy state, respectively. Tunability of the material’s overall performance in terms of optical contrast, switching kinetics, coloration efficiency and cyclic stability based on the lattice water concentration was elucidated in this work. Furthermore, the fabricated device displays self-bleaching property and has a short-term “memory” effect that may broaden its potential for other applications.