Thermal Annealing Effect on Properties of Nickel Oxide (NiO) Thin Films for Photovoltaic Applications

In this study, the impact of annealing temperature (T_A) from room temperature (RT) to 400 °C on the structural, optical and electrical properties of NiO thin films deposited using sol‐ gel spin coating technique on glass substrate is presented. A theoretical approach is also employed to calculate the open circuit voltage (V_OC) from the energy band gap (E_g) value, fill factor (FF), short circuit current (I_SC), and power conversion efficiency (PCE) of the material for solar cell applications. Crystallinity improvement is observed upon annealing the NiO thin films and the average size of crystallites varies from 28 to 34 nm with a maximum value observed for 300 °C annealed film. The SEM micrographs confirm the nano form of NiO nanoparticles, with particles that are between 73 and 100 nm in size. All the films are semitransparent with transmittance >55% and the thin film annealed at 300 °C exhibited 88% transmittance in the visible region, making it a promising option as a transparent conducting oxide (TCO) in photovoltaic applications. The I–V curves display a non‐linear behaviour for all annealing temperatures. The conductivity increases with an increase in T_A and the film annealed at 300 °C shows the highest conductivity.