Influence of annealing on properties of spray deposited nickel oxide films for solar cells.
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Nickel oxide thin films were deposited on soda lime glass substrates by spray pyrolysis technique (SPT). Post-deposition annealing was carried out at 450 oC. Effects of annealing on the structural, elemental and surface morphological properties of the thin NiO films were investigated. XRD confirms polycrystalline with cubic crystalline structures of deposited and annealed NiO films. Preferred orientation was along (1 1 1) peak with intensity along (2 0 0) peak improved by annealing. The annealing process improved on formation of crystalline phases. XRD patterns have peak diffraction at (2θ = 37 o, and 43 o) for (1 1 1) for deposited and annealed. Peak diffraction at (2θ = 64 o, and 79 o) for (2 0 0) planes for 0.1 M and annealed respectively. Annealing improved on the film thickness by over 10 %. Surface morphology of deposited and annealed NiO films reveals nanocrystalline grains with uniform coverage of the substrate surface with randomly oriented morphology. Larger flakes are formed as a result of the annealing process. EDX elemental NiO films composition revealed presence of Ni and O elements in NiO films. A decrease in oxygen concentration was also observed confirming positive effect of annealing as an optimization process. Optimization of nickel oxide deposition process parameters offers opportunities for efficient and affordable solar cells.