Among the transition metal oxides, tungsten trioxide (WO3) has attracted much attention and has been widely studied due to its many interesting structures and defect characteristics. The numerous applications of WO3 optical and electronic devices include electrochromic (EC) smart windows, flat panel displays, tunable EC photonic crystals, and gas sensors. However, its higher band gap energy (2.6-3.6 eV) limits its application. Therefore, the low frequency near infrared light (NIR) cannot be blocked.

Tungsten pins, also named tungsten needles or tungsten electrodes, are a typical tungsten product with purity of 99.95%. It has a silver-white appearance, a slender structure, a length of 20mm-1000mm, and a diameter of 0.3mm-10mm. Usually, the product is customized. 

Electrochromism (EC) is a phenomenon that induces a reversible optical change (coloration/bleaching) in a material by applying a small electric field. Tungsten oxide (WO3) is the most widely studied electrochromic material due to its outstanding electrochromic (EC) properties. Materials that can continuously and reversibly change color under reversible electrochemical processes are called electrochromic materials, which have been widely used to fabricate light modulation devices. Among these devices, anti-glare car mirrors have been commercialized, and smart windows are currently driving intensive development.

A collimator, a device used to transform the diverging light or other radiation from a point light source into a parallel beam. Special measurements in spectroscopy and in geometric and physical optics require this kind of collimation.