Fabrication of flexible Al-doped ZnO films via sol-gel method

1% Al-doped ZnO transparent and conducting thin films on flexible polyimide (PI) substrates were successfully synthesized by the conventional sol-gel spin coating method. All the films with different number of layers (9, 10 and 11) retained a hexagonal wurtzite structure of ZnO and showed preferential c-axis orientation. Good adhesion was evidenced by dense microstructure and homogeneously distributed grains of the films on flexible PI substrates. The average transmittances reached 70% for all the films above a cut-off wavelength of similar to 500 nm originated from PI substrates. Comparing to the resistance of films annealed in air, the electrical conductivity could be enhanced by further vacuum (P similar to 10(-2) Pa) post-annealing, and lowest resistivity of 2.52 x 10(-1) Omega cm was obtained in the film with 10 layers. (C) 2015 Elsevier B.V. All rights reserved.