Electrodeposition Of Cuprous Oxide Semiconductor Films And Their Photovoltaic Application

Energy depletion and environmental pollution are two thorny problems facing the human society, due to the over-exploitation of traditional fossil energy. Developing clean and renewable energy is an inevitable trend. The solar cell is one of clean, non-polluting and renewable energy source. Cuprous oxide (CU2O) is a p-type direct band gap semiconductor with a band gap of-2.0 eV, which leads to a theoretical limit of～20% for the energy conversion efficiency of Cu2O-based solar cells. As a non-toxic material, Cu2O can be easily prepared in a large scale due to the natural abundance of copper. Therefore, it is of great interest to explore the use of Cu2O for solar cells. Compared with other preparation methods, electrochemical deposition has the advantages such as low cost, low temperature, large scale manufacturing, being able to deposite films on substrates with complex morphology, and also its facility to control morphology, compositions and doping for the deposited materials. In this work, electrochemical deposition was chosen to prepare the p-type Cu2O films in alkaline copper lactate solution system on the n-type TiO2 nanorod array substrates, and then the FTO/TiO2/Cu2O/Au heterojunction solar cell were manufactured. Characterizations of scanning electron microscope (SEM), X-ray diffraction (XRD), transmission electron microscope (TEM), UV-Visible absorption test and current density-voltage test et al. were used to analyze the morphology, structure and photovoltaic effect of FTO/TiO2/Cu2O/Au solar cells. The primary significant results are summarized as follows:(1) TiO2 nanorod arrays were prepared by hydrothermal method on the FTO substrate. Every single TiO2 nanorod was rutile single crystal with a band gap of about 3.0 eV. The length of the nanorod array was able to be controlled by the hydrothermal reaction time.(2) Successfully electrodeposited Cu2O films on the TiO2 substrates and fabricated good p-n junction. The concentration of electrolyte, applied voltage, the value of pH, and the deposition time were studied to show their effects on the quality, morpgology and thickness of the Cu2O film.(3) FTO/TiO2/Cu2O/Au heterojunction solar cells were successfully manufactured and the highest efficiency is up to 1.25%. Some analyses about this structure were studied. One-dimensional TiO2 nanorod arrays can act as a fast transport channel for carriers and enlarge contact area of the p-n junction, resulting in the more effective separation of carriers at the interface. Every single TiO2 nanorod is pure rutile single crystal, which can partly reduce the carrier recombination losses. The TCO glasses used in this structure of FTO/TiO2/Cu2O/Au can reduce the loss of efficiency caused by light-blocking.