Cobalt-doped MoO3 thin films and dual-band electrochromic devices with excellent cyclic stability

Electrochromic (EC) technology has played a pivotal role in elevating the prominence of smart windows by enabling them to alter their color and effectively manage the level of transparency. Nanostructured molybdenum trioxide (MoO3) thin films are highly promising for the development of EC technology. However, the production of uniform, crack-free and durable MoO3 thin films through conventional deposition methods is still a challenge though these properties are critical for achieving prolonged cyclic stability. In this work, we demonstrate the use of ultrasonic spray deposited bare MoO3 and cobalt-doped MoO3 (MoO3:Co) thin films for EC applications. Cobalt (Co) doping is shown to significantly improve the cyclic stability when compared to the bare MoO3 films. Furthermore, MoO3:Co films have exhibited significant performance in novel dual-band electrochromic devices (ECD). After 5000 cycles, the MoO3:Co electrodes showed significantly higher capacitance retention (92%) compared to the bare MoO3 thin film electrodes (54%). Moreover, MoO3:Co electrodes exhibited a higher maximum transmittance change than the bare MoO3 electrodes. Dual-band ECDs showed excellent cycling performance up to 5000 cycles with a capacitance retention of 99%. Obtained results demonstrated the potential of the ultrasonic spray deposition method for MoO3 thin film based EC windows and dual-band ECDs with excellent cyclic stability.