Solution processed aluminum-doped ZnO thin films for transparent heater applications

A study was carried out to tailor the properties of ultrasonic spray pyrolysis deposited Al-doped ZnO (AZO) thin films suitable for transparent heater applications. For this purpose, the influences of solvent/precursor type and molarity, Al-doping concentration, nozzle to substrate distance, solution flow rate, carrier gas flow, substrate temperature, and post-deposition annealing on the microstructure, electrical, optical properties, and heating/ deicing behaviors of the films were investigated. The optimized heaters were produced on 50 x 75 mm(2) glass substrates at 400 degrees C with 750 nm thickness and annealed under forming gas for 90 min. This sample revealed a good sheet resistance value of 38.7 Omega/square and 83% transmittance in the visible region. Heating/deicing tests showed that the maximum achievable surface temperature was 76 degrees C under an applied potential of 12 V and all ice/water can be removed completely within 250 s. In addition, the AZO heater exhibited a very high thermal resistance value (409 degrees C cm(2)/Watts) with stable and reversible heating behavior.