Investigating The Effects Of Nitrogen Annealing And Doping On The Photoelectric Properties Of Cuprous Oxide Thin Films

With the rapid development of the global economy,human demand for energy continues to increase.The environmental problems brought about by the large-scale use of fossil fuels cannot be ignored.Therefore,there is an urgent need to develop new energy sources with abundant reserves,cleanliness and low prices.As one of the most primitive energy sources,solar energy undoubtedly meets the requirements of abundant reserves and cleanliness.Therefore,the preparation of low-cost solar cells is a topic that people need to overcome at present.Cuprous oxide(Cu2O),as a P-type oxide semiconductor,has the advantages of abundant raw material reserves,low preparation cost,and non-toxicity,which has aroused people’s interest in its application in the field of solar photovoltaics.However,the photoelectric conversion efficiency of Cu2O-based solar cells is low,because the existence of a large number of defects in polycrystalline Cu2O films leads to lower carrier mobility and carrier concentration.Therefore,the preparation conditions of Cu2O films are optimized to improve film quality and reduce Defects in thin films to improve carrier mobility and carrier concentration are the key to the development of Cu2O-based solar cell technology.In this paper,Cu2O thin films were prepared by reactive RF magnetron sputtering technology,and annealed under different nitrogen gas pressures.The effects of nitrogen annealing on the structure and optoelectronic properties of Cu2O thin films were systematically studied.The research results show that nitrogen annealing can improve the crystal quality of Cu2O thin films and inhibit the appearance of CuO second phase.Nitrogen annealing can improve the carrier mobility of Cu2O thin films.The variable temperature Hall effect test found that the carrier mobility of the as-deposited Cu2O thin film increased with the increase of temperature,indicating that the scattering mechanism of the grain boundary to the carriers was dominant;after nitrogen annealing,the carrier mobility of the Cu2O thin film increased As the temperature increases,it first increases and then decreases,indicating that the carrier transport changes from the grain boundary scattering mechanism to the phonon scattering mechanism.Through data fitting,it was found that the grain boundary carrier transport barrier of Cu2O thin films decreased from 54.36 meV to 35.06 meV after nitrogen annealing.X-ray photoelectron spectroscopy(XPS)results indicated that nitrogen molecules existed in the Cu2O films after nitrogen annealing.The research results show that nitrogen annealing causes nitrogen molecules to enter the grain boundary region of the Cu2O film,passivate the grain boundary defects,thereby reducing the scattering of carriers at the grain boundary,thereby improving the current carrying capacity of the Cu2O film.child mobility.The effect of nitrogen doping temperature on the structure and optoelectronic properties of Cu2O thin films was also investigated.The research results show that nitrogen doping can change the preferred orientation of Cu2O thin films.At the same time,nitrogen doping can obviously reduce the grain size of Cu2O films,and the film density decreases with the decrease of temperature.With the decrease of nitrogen doping temperature,the carrier concentration of Cu2O thin film gradually increases,and the resistivity decreases gradually,and the resistivity is the lowest at 8.48 Ωcm.The high nitrogen doping temperature leads to the decrease of the optical bandgap of Cu2O thin films,indicating that nitrogen doping changes the energy band structure of Cu2O,and nitrogen atoms may replace oxygen atoms to form No during nitrogen doping.The Cu2O thin film with nitrogen doping temperature of 300℃ has the smallest optical bandgap(2.16 eV),high carrier concentration and low resistivity.Nitrogen annealing causes molecular nitrogen to enter the grain boundary position of the Cu2O film,which acts as a passivation of the grain boundary and improves the carrier mobility of the Cu2O film;while nitrogen doping causes nitrogen atoms to enter the Cu2O lattice,which can improve the Cu2O film.carrier concentration and reduce the optical band gap.Therefore,both nitrogen annealing and nitrogen doping can be used as effective means to improve the photoelectric properties of Cu2O thin films.