How to Improve the Electrochromic Properties of Tungsten Trioxide

From the mid-1970s to the early 1980s, most studies on the electrochromic properties of tungsten trioxide have focused on electronic display devices. However, due to the limitation of their lower color conversion rate, since then, research has been turning to new fields such as smart windows. Although the latter is less demanding for color response time than display devices, until now, this is still the focus of widespread concern.

Since then, research has been turning to new fields such as smart windows. Although the latter is less demanding for color response time than display devices, until now, this is still the focus of widespread concern. To achieve its wide application in the field of building curtain wall, we need to make great improvements in many aspects such as preparation technology, cost control, weatherability and cycle life. The pure solid state electrochromic device which incorporates the lithium element into the tungsten oxide and uses the lithium ion as the conduction medium can achieve a substantial improvement on environmental durability and chemical stability.

In addition to doping, the introduction of nano structure is another method that can effectively improve the performance of WO₃ discoloration in recent years, using nanotechnology, through the adjustment of structure, the method of improving the discolouration property has been more and more mature. Therefore, the research of blue tungsten oxide has been redirected towards a more compact and stable structure, but the color structure is relatively poor. The rough surface and dense pores inside the nanocrystalline network will help to increase the transmission channel, accelerate the ion diffusion and shorten the migration path, so as to achieve the purpose of improving the chromotropic property of tungsten oxide. At the same time, the dense and stable crystalline structure can ensure good chemical stability, effectively control the dissolution loss of the electrochromic layer to the ion conducting layer, and prolong the service life of the device.

Although many efforts have been made in the preparation of porous nano crystalline tungsten oxide in recent years, the market is still mainly based on the relatively mature amorphous tungsten oxide. Therefore, while improving the discoloration performance, it is also necessary to consider the later batch production and large-scale application of the porous nanocrystalline thin film, the cost control and the simplification of the process, which are also indispensable key requirements.

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