Strontium and Copper Co-doped Nickel Oxide Hole Transport Layer for Efficient and Stable Perovskite Solar Cells /

Abstract

NiOx thin film is used in a wide range of applications just as smart windows, conducting electrodes, chemical sensors, and dye-sensitized photocathodes, due to its simplest processing, low material cost, high optical transparency, and wide band gap. However, the electrical conductivity of NiOx is low. Therefore, to enhance the electrical conductivity doping of NiOx is used. In this paper, un-doped, and Sr, Cu codoped nickel oxide thin films have been deposited on a glass substrate by using the sol-gel spin coating technique. The basic materials used were strontium nitrate, copper sulfate pent hydrate, and nickel acetate tetra hydrate. 2-Methoxyethanol is used as a solvent. The Effect of Sr and Cu on the Structural, optical, and electrical properties of NiOx thin film were investigated by using X-ray diffraction spectroscopy (XRD), Scanning electron microscopy (SEM), UV-Visible spectroscopy, and Hall effect measurement. The XRD results show that the undoped and Sr, Cu co-doped NiOx thin films have a simple cubic structure with three identical characteristic peaks at 2θ = 37.299°, 43.301°, and 63.094° corresponding to the (111), (200), and (220) planes. SEM images demonstrate that both the undoped and Sr, Cu co-doped NiOx thin films have smooth, continuous, and pinhole-free surfaces. The transmission and absorption spectrum of Undoped and Sr, Cu co-doped NiOx thin film were studied by using Ultraviolet-visible spectroscopy. It shows that the transparency of the film decreases from 85% to 78% as the concentration of Sr and Cu increases respectively. The band gap was calculated by using Tauc equation. Hall Effect measurement was used to calculate the electrical conductivity, resistivity, carrier concentration, and carrier mobility. But when the concentration of Sr and Cu increases to 3 wt. % Sr and 3 wt. % Cu the electrical conductivity, carrier concentration, and carrier mobility decrease, and resistivity increases. Therefore, the best suitable sample is 2 wt. % Sr and 3 wt. % Cu co-doped NiOx thin film. It is concluded that Sr and Cu co-doping can effectively improve the structural, morphological, optical, and electrical properties of NiOx thin films. Therefore, Sr, Cu co-doped NiOx thin film can be used in all the above applications.