Investigation On The Preparation And Properties Of Cu₂O And Cu₂O-ZnO Based Heteroiunctions

Cuprous oxide (Cu2O), with a direct band gap of2.17eV, is a natural p-type semiconductor owning a high absorption coefficient in the visible light region. Zinc oxide (ZnO), an intrinsic n-type semiconductor with a direct band gap of3.37eV, is considered to be a promising partner with Cu2O for p-n heteroj unction. Cu2O-Zn0heteroj unction has shown great potential in photovoltaic, photocatalysis, and photochemical catalysis applications due to the low-cost, nontoxicity, abundance and variety of preparation methods. The resistivities of the Cu2O films in present ZnO-Cu2O heteroj unction solar cells are relatively high, which seems to be the main problem for the low photoelectric conversion efficiency.In this work, the Cu2O thin films were prepared by electrochemical deposition and magnetron sputtering. Cu2O/ZnO and Zn0/Cu20heteroj unctions were fabricated by magnetron sputtering in different growth sequence. The energy band alignments and I-V characteristics of the reverse ordered Cu2O and ZnO heteroj unctions have been measured. Main research works are as follows:(1) Cu2O films and Cu20/ZnO heteroj unction were prepared by electrochemical deposition. The value of pH and the temperature were studied to show their effects on the crystal structure and morphology of the Cu2O films. The optical and photocatalysis property of the Cu2O films were investigated.(2) Cu2O and ZnO films were prepared by magnetron sputtering. The effects of O2partial pressure and the temperature on the properties of the Cu2O films were studied. Single-phase Cu2O film with a resistivity of88.5Ω·cm, a Hall mobility of16.9cm2/V·s and a carrier concentration of4.19×10115cm-3were obtained. Using vacuum annealing method to obtain single-phase Cu2O thin film were investigated intensely.(3) Cu20/ZnO and Zn0/Cu20heterojunctions were fabricated by magnetron sputtering in different growth sequence. XPS was used to measure the band alignments of the Cu20-ZnO heterojunctions fabricated in reversed growth sequence. The valence band offsets (Δer) of the two kinds of Zn0-Cu20heterojunctions were found to be different with each other. The mechanism lead to the difference were investigated and the I-V characteristics of the heterojunctions were measured for the further investigation of the application of Cu20-ZnO based photoelectric devices.