Electrochemical Deposition Of P-typeand N-type Cu₂O Films

Solar energy is a renewable energy and is friendly to the environment. People have paid more and more attention to the development and utilization of solar energy, especially to the study of solar cell materials in today’s resources exhaustion conditions. Cuprous oxide (Cu2O) is an environmentally friendly semiconductor materials with a direct band gap around1.9～2.2eV, and is a suitable material for application in optics, electromagnetism, photo-catalysis and photovoltaics. The advantages of this material are its abundance, non-toxicity, low-cost fabrication and high photoelectric conversion efficiency. Usually, homojunctions are highly desired for the use in microelectronic devices since they exclude interface strain, and accordingly they have a better performance than heteroj unctions in relevant applications.In this work, the basic theory and techniques of solar cells are comprehensive analyzed. The electrochemical deposition conditions are explored by electrochemical workstation, and Cu2O films are reproducibly deposited on FTO substrates adjusting the pH value of the electrolyte. The phase constituents, crystal structure, microstructure and chemical compositions of Cu2O films were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and EDS techniques. In addition, the conductive type of the samples was measured using the electrochemical workstations (PARSTAT2273and CH1660D). an UV enhanced xenon lamp (7ILX500p) and a three-electrode system. According to the experimental data, the conclusions are as below:(1) In order to achieved the best deposition conditions, the electrochemical deposition parameters of Cu2O were explored:the best work potential was-0.241V in acid/neutral condition and-0.4V in alkaline condition respectively, and the best deposition temperature was50℃.(2) In this work, the uniform, dense, smooth and chemically stable Cu2O films were successfully synthesized on FTO substrates by electrochemical deposition with the same electrical potential but different pH values.(3) The photoelectric performance of the samples was measured. The results show that the conductive type of Cu2O is closely related to the pH value of the electrolyte.In an acidic solution. as pH=4,5for example, the Cu2O thin films are n-type semiconductors. while in an alkaline solution, the Cu2O thin films are p-type, with pH values ranging from6to11.Although the relationship between the deposition conditions and the intrinsic defects is speculative at this moment, in this work we have found an innovative method to prepare Cu2O thin films with different conduction type only by adjusting the pH value of the electrolyte. That in turn might be used to construct Cu2O homojunctions for solar photoelectric cell applications.