Development of hole transport layer based on NiO nanoparticles for Perovskite solar cells

Abstract

Nickel oxide (NiO) based nanoparticles have been prepared by following conventional chemical precipitation method, by maintaining the pH ~10 with the help of NaOH of the aqueous solution of 0.1M Ni(NO3)2.6H2O followed by centrifuged at 6000rpm. The obtained precipitate has been dried at 80oC for 6 hours and obtained green powder was annealed at 270°C for 2h. Powder X-ray diffraction data suggests the formation of cubic structure of nickel oxide. UV-Visible spectroscopy is used to determine optical properties of NiO including optical transmittance, optical absorbance and bandgap calculations (Band gap =3.5eV and Transmittance = 92%). Further, we prepared thin film of aqueous dispersed nickel oxide (NiO) by using spin coating method at 3000rpm for 60s and then annealed at temperature 400°C for 30 minutes to remove the moisture content, if present in sample. The effect of concentration of Ni(NO3)2.6H2O solution on structural properties and optical properties was studied by using X-ray diffraction and UV-visible spectroscopy techniques, respectively. It is found that with sequential increment in concentrations of the NiO solution (0.1M, 0.2M and 0.4M) the transmittance decreases (92% to 81%) and band gap decreases (3.51eV to 3.49eV). In order to enhance the conductivity of hole transporting layer, we prepared the copper doped nickel oxide nanoparticles and thin films at the Cu percentage of 1, 2, 4 %, in turn, found to be the slight increment in absorbance but decrement in transparency (92% to 86%) of the thin film. In addition, with increment of the copper concentration (1-4%) the crystallinity of the Cu doped NiO also affects and it varies from 14 nm to 5 nm, conductivity was also found to increase. In order to fabricate the device, the all inorganic perovskite solar cell FTO/TiO2/CsPbBr3/NiO/Ag. The dark current profile of the device shows similar response as that of a p-n junction diode. However, device does not show proper photo-response in presence of light.