Diameter dependent transparency changes of nanorod-based large-area flexible smart window devices

Abstract

Saving energy and designing an environmentally friendly atmosphere in modern buildings will require smart windows that can adapt to a variety of conditions and requirements, such as weather, human load and personal desire. The key element of such windows is the material system that transmits light in and out of the building in a controlled manner. To address the need for such a system, here we report the fabrication of novel, flexible, large-area devices that are based on suspended organometallic nanorods. As a result of the detailed characterization and extensive optimization of nanorod synthesis and device fabrication, our fabricated devices achieve superior optical and stability performances, with optical modulation as high as 73.7% (the highest value reported to date) and bending capability up to ∼180 degrees without any structural damage. This performance is further reinforced by repeated switching testing between high (“on”) and low (“off”) optical transmittance states over 500 cycles. Finally, we are able to scale up the fabrication of such devices to large areas (24 cm by 9 cm, size limited by our laboratory-scale doctor blade), underlining the possibility of adopting the results reported herein for future flexible smart windows and electronics. An interesting finding that the eventual SPD performance is indeed largely dependent on the diameter of the nanorods instead of their aspect ratios provides useful guidelines for future development.