Structural, optical and electrical properties of NiO thin films for hole transport layer in chalcogenide and perovskite materials based solar cells

Abstract

This work presents the fabrication of NiO thin films via versatile sol-gel spin coating method and investigation of annealing effects on their physical properties. After the deposition process, the NiO thin films underwent annealing process at different values of temperatures ranging from 200°C to 350°C for one hour duration. XRD patterns confirmed the polycrystalline nature, along the preferred orientations (110) and (101) planes. Nanoparticles in NiO thin films demonstrated an increase in crystallite size with rising annealing temperatures, reaching a maximum size of 49 nm at annealing temperature 300°C. FTIR patterns revealed Ni-O bands at 472 cm-1 in the far infrared region. UV spectroscopy showed that the average transmittance of the NiO thin films increases 91% to 94% as a result of increasing the temperature during annealing. While the band gap decreases and reaches the lowest value 3.94 eV at 300°C. The hot probe tests of the fabricated nickel oxide thin films verified their p-type nature while the four-point probe technique showed that resistivity decreases at higher annealing temperatures. Based on these enhancements of physical properties, NiO thin films could be suggested as promising candidates for hole transport layer applications in chalcogenide and perovskite materials based solar cells.