All-in-one dual responsive hydrogels for thermoelectrochromic (TEC) devices

Abstract

The development of new functional materials plays a pivotal role in creating novel materials for devices such as displays or smart windows, offering new possibilities for indoor comfort and energy saving. Most devices only respond to a single external stimulus (electrical, light, thermal) missing on the potential of incorporating multiple responses. Herein, all-in-one thermo- and electrochromic hydrogels for dual responsive displays are presented. In these multifunctional materials, different viologens and thermoresponsive polymers (poly(N-isopropylacrylamide) or poly(N-vinylcaprolactam)) were incorporated simultaneously into hydrogels. By applying these hydrogels on simple sandwich type FTO based devices, it was possible to create single layered dual responsive devices. These devices could change their opacity and color due to their thermochromic (TC) and electrochromic (EC) properties, being able to combine both changes at the same time. The devices showed high optical contrasts, from their almost fully transparent bleached state to their TC and EC states (<5% and ≈70% transmittance at 600 nm, respectively). All phase changes were proven to be reversible by cycling between the bleached, TC, EC and dual TEC states for consecutive times. Therefore, these hydrogels can offer new simple smart window or display designs.