Nanohybridization of molybdenum oxide with tungsten molybdenum oxide nanowires for solution-processed fully reversible switching of energy storing smart windows

Abstract A multi-functional electrochromic material which modulates light over a wide spectral range and stores electrical energy is an intriguing substance, which would lead to a variety of novel applications, such as smart windows for energy-efficient buildings, solar power storage, nonemissive displays, electronic paper, optoelectronic switches, and variable-reflectance mirrors/surfaces. Developing such a versatile material entails merging the electrochromic phenomenon with electrical-chemical energy conversions in an electrochromic-battery platform. However, the challenges related to transition metal oxide electrochromic-batteries include poor energy storage, low optical contrast, and high fabrication cost. Here, we demonstrate the synthesis of aqueous nanocrystalline colloidal molybdenum oxide in a matrix of tungsten molybdenum oxide (MoO 3 -W 0.71 Mo 0.29 O 3 ) for solution-processed fully reversible switching electrochromic-battery electrodes. The hybrid material exhibits both 50% optical contrast modulation over a wide optical bandwidth and an improved Columbic efficiency. An 8 × 8 cm 2 energy storing smart (ESS) window is assembled to demonstrate a functional prototype that can power an LED for more than 10 min when charged under −2.5 V for 1 min. The enhanced electrochromic performance, high energy storage capacity, simple solution processability, versatility for large area fabrication, and low cost make this nanocrystalline MoO 3 -W .71 Mo .29 O 3 composite a promising material with the potential to be deployed ubiquitously in energy-efficient smart window architectures.