Fabrication and characterization of transparent p–n and p–i–n heterojunctions prepared by spray pyrolysis technique: Effect of post-annealing process and intrinsic middle layer

In this paper, p–n and p–i–n heterojunctions based on transparent semiconducting oxides are fabricated employing the spray pyrolysis technique. The prepared p-NiO:Li/n-SnO2:F (bi-layer) and p-NiO:Li/i-ZnO/n-SnO2:F (tri-layer) junctions are structurally, electrically and optically characterized, and the effect of insertion of the intrinsic buffer layer (i-ZnO) followed by post-annealing is investigated through I–V measurements. The measurement results for the proposed p-NiO:Li/n-SnO2:F device show that the forward threshold and the reverse breakdown voltages are about 0.4 and −2.8 V, respectively. By applying the middle layer, the forward threshold and reverse breakdown voltages reach ∼1 and −4.2 V; then by post-annealing this element at 700 °C for 30 min, the mentioned voltages reach about 1.6 and −3.1 V, respectively.