Copper nanowire network based transparent thin film heaters

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2018
Tigan, Doğancan
Metallic nanowire random networks are highly promising as transparent thin film heaters (TTFHs) due to their significant optoelectronic performance and thermal conductivity. Typically silver nanowires (Ag NWs) are utilized as TTFHs but in recent years, copper nanowires (Cu NWs) started to replace them in many applications as an economic alternative. The electrical conductivity of Cu is almost equal to that of Ag and it is much cheaper than Ag at least in bulk form. However, stability of Cu NWs is a lot poor compared to that of Ag NWs due to ease of oxidation upon air exposure. The problem gets even worse at elevated temperatures considering TTFH applications. Therefore, a protection layer to be deposited onto Cu NW networks is necessary for their large scale utilization in TTFHs. In this study, aluminum oxide (Al2O3) and zinc oxide (ZnO) shells were deposited onto Cu NW networks by atomic layer deposition (ALD) method. Cu NW networks with a sheet resistance of 10 Ω/sq failed only after attaining a temperature of 100 °C due to oxidation. On the other hand, deposition of only 5 nm Al2O3 and ZnO shell layers onto Cu NW networks (10 Ω/sq sheet resistance at 80.8% transmittance and 15 Ω/sq sheet resistance at 84.4% transmittance) increased the maximum attainable temperatures to 153 °C and 139 °C, respectively. This was a clear indication of oxidation protection by the deposition of the shell layer onto Cu NW networks. Moreover, in order to further increase the protection level, the effect of oxide shell thickness was investigated in sacrifice of network transmittance. Attained maximum temperatures were increased up to 309 °C and 237 °C for 50 nm thick Al2O3 and ZnO shell layers on Cu NW networks, respectively. Moreover, prominent heating rates of 14 °C/s and 12 °C/s were obtained from these core shell networks with Al2O3 and ZnO shells, respectively. Finally, an extensive parametric study on NW density, type and thickness of metal oxide shells in comparison to optoelectronic properties of networks and their thermal response is reported. The performance of the networks reported herein lie among the highest achieved for Cu NW TTFHs. In order to demonstrate the feasibility of these networks as TTFHs in a real life application, they were utilized as defrosters.

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Citation Formats
D. Tigan, “Copper nanowire network based transparent thin film heaters,” M.S. - Master of Science, Middle East Technical University, 2018.