Investigation of physical properties of spin coated Ni1−xZnxO (x = 0, 0.05, 0.07, 0.09) thin films for application as hole transport layer for perovskite solar cells

The unique physical properties of the inorganic NiO thin film make it a more appealing candidate for use as a hole transport layer. However, these physical properties are strongly influenced by doping a semiconductor into a NiO lattice. In this study, we inspected the doping effects of zinc on the structural, optical, morphological, and electrical properties of the Ni1−xZnxO thin films fabricated via spin-coating technique, demonstrating their potential as hole transport layers. XRD spectra exhibited a small (200) peak with low intensity, indicating weak crystallinity in the pure NiO and zinc doped NiO thin film. FTIR spectra revealed the existence of the Ni-O groups at four bending positions (456 cm-1 , 446 cm-1 , 450 cm-1 , and 451 cm-1 ). UV-visible spectra analysis revealed an increase in bandgap energy from 3.88 eV to 3.98 eV with the enhancement of zinc concentration from 0 to 0.09. The homogeneous morphology hidden within pure and doped NiO thin films was investigated using scanning electron microscopy. The Hall effect tests revealed that adding zinc to pure NiO thin film increased carrier concentration and decreased resistivity.