Tungsten Trioxide Film Material Preparation by Immersion Pulling Method

At present, the commonly used preparation methods of tungsten trioxide thin films are atomic layer deposition, chemical vapor deposition, electrodeposition and so on. However, the tungsten trioxide thin film method developed based on the above methods requires high equipment, complex preparation process, high cost, and can not prepare large-area films.

Therefore, it is imperative to develop a tungsten oxide PEC semiconductor electrode material with simple production process, low cost, high purity and high photoelectric conversion efficiency.

Some scholars have proposed a scheme of preparing tungsten trioxide thin film material by dipping and pulling method. The process of this scheme is concise, easy to operate, and the success rate is high. The concrete operation steps are as follows:

Conductive glass substrate cleaning: FTO conductive glass was immersed in KOH isopropanol saturated solution for 24 hours; washed with distilled water; ultrasonic cleaning with distilled water for 30 minutes; ultrasonic cleaning with acetone for 30 minutes; ultrasonic cleaning with absolute ethanol for 30 minutes; ultrasonic cleaning with secondary deionized water for 30 minutes, then rinsed three times, and N2 blow-dry for standby.

9.8g (NH₄) ₆W₇O₂₄·6H₂O₂ was dissolved in 20ml secondary deionized water, 5g PEG 1000 was added, magnetic force was stirred continuously for 4h, and then the transparent precursor was obtained by water bath at 80 ℃ for 2h.

FTO conductive glass was extracted from the prepared precursor solution at a speed of 2 cm/min by dipping and drawing method. It was placed for 5 minutes and dried in an oven at 70 ℃ for 1 hour. Then it was heated to 500 ℃ at a rate of 5 ℃/min for 3 hours. When the furnace door is opened and cooled naturally to room temperature, nanometer tungsten trioxide film can be obtained.

Due to the use of water-soluble polytungstate as the precursor and the addition of dispersant and modifier, the final tungsten trioxide film and the base are very firm and will not fall off. In addition, the precursor solution has been kept for more than three months without agglomeration and precipitation. It remains stable and can be reused. It is not only easy to operate, but also greatly reduces the cost of preparation. The tungsten trioxide film prepared by this process has good photoelectric properties. Under the mercury lamp with 60 mW/cm² light intensity, the current density of 1.5V under bias voltage reaches 3.9mA/cm2. The photoelectric properties are as follows: It is 2-3 times higher than WO₃ prepared by dissolving tungsten powder in hydrogen peroxide.

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