Transparent conductive ZnO:Al/Cu mesh composite film and its electric heating performance

Transparent conductive films (TCFs) play an indispensable role in optoelectronic devices because of their high conductivity and high optical transmittance. In order to obtain indium-free transparent conductive films with better performance, we need to improve the conductivity, while not damaging the transmittance. Metal mesh is highly conductive but prone to oxidation and abrasion, while transparent conductive oxide (TCO) is stable but less conductive. Thus, we composite the metal mesh with the stable TCO to achieve complementary advantages. In this work, we fabricate a hexagonal Cu mesh and then cover the Cu mesh with Al-doped ZnO (AZO) film by using lithography and magnetron sputtering. The line width and length of mesh are 15 µm and 150 µm, respectively, which are not visible to the naked eye. The effect of AZO growth temperature on the properties of such AZO/Cu mesh composite film is studied and the optimal temperature is 300 ℃. By designing the mesh and optimizing the process, the transmittance (400–800 nm), sheet resistance and FoM of AZO/ Cu mesh composite film reach 86.4%, 4.9 Ω/sq and 4.73 × 10–2 Ω–1, respectively, thus possessing both transparent and conductive property. Because of its low cost, competitive optoelectronic performance and stability, the potential applications of AZO/Cu mesh composite film in transparent electronics are fantastic. When used as a transparent conductor to connect LED to 3 V DC power, the luminance of LED in series with AZO/Cu mesh composite film is lighter than that of AZO film and Cu mesh. According to the Ohmic heating effect of electric current passing through a conductor, AZO/Cu mesh composite film can be designed as electric heating film. At low voltage safe for human body, AZO/Cu mesh composite film can implement fast, uniform and stabile heat. In the cyclic electric heating test, the AZO/Cu mesh composite film can be heated rapidly to 175 ℃ all the time, showing a fast temperature response and stable cyclic performance. More importantly, the AZO is itself transparent and conductive and prevents the metal from oxidizing effectively, thus ensuring the overall performance and maintaining the electric heating response. The experimental result and simulation application show that the AZO/Cu mesh composite film has a great potential application in transparent and heating film for defogging and defrosting glass.