Preparation And Research Of Nickel Oxide Thin Films And Their Application In Solar Cells

N-type transparent conducting oxide(TCO) such as ITO and FTO is one of the important materials for the optoelectronics. Counterpart P-type TCO is also another important semiconducting material, but the optional materials are less. Nickel oxide(Ni O) would be a promising candidate for P-type TCOs with the band gap from 3.6 e V to 4.0 e V. In addition, it has been already attracted much attention because of their attractive electrical, optical, magnetic and thermoelectric as well as high chemical resistance. Especially, these unique properties of Ni O films allow them to be used in solar cells.This thesis presents the high-quality Ni O thin films by a chemical solution method of polymer-assisted deposition. After the growth of Ni O thin films, they are attempted to use in solar cells as hole-transporting layers. To optimize the performance of solar cells, doping the Ni O films with Li+ and adjusting the films’ thickness have been done. The main subjects of this thesis are concluded as follows:1. High-quality epitaxial Ni O thin films are grown on(0001) Al2O3 substrates. First, the precursor solution is fabricated by polyethylenimine(PEI) combined with nickel chloride hexahydrate(Ni Cl2·6H2O). Then the precursor solution is spin-coated onto(0001) Al2O3 substrates. Finally, the precursor films are annealed in an ambient air to grow epitaxial Ni O thin films. The X-ray diffraction(XRD), transmission electron microscopy analysis(TEM), field-emission scanning electron microscopy(FESEM), atomic force microscopy(AFM), ultraviolet-visible(UV-Vis) spectrometer, physical property measurement system(PPMS) and X-ray photoemission spectroscopy(XPS) are performed to study the microstructures, the surface morphology, the epitaxial relationship, the optical, electrical property and valence state.2. The Ni O thin films are applied in polymer solar cells as hole-transporting layers. Ni O films replace PEDOT:PSS to avoid acidic corrosion of the ITO and block electron more efficiently. To optimize the performance of solar cells, the thesis also investigates the films doped with Li+ and the films’ thickness. In addition, the Ni O thin films are also attempted to apply in new-type halide perovskite solar cells as hole-transporting layers. The Ni O films in the structure of FTO/Ni O/perovskite/PCBM/Ag function as electron blocking and hole extraction layers for the perovskite solar cells. We adjust some parameters of the Ni O films to improve the efficiency of the solar cells.