Preparation Of Cu₂O-based Transparent Pn Junction And Its Photoelectric Conversion

The transparency of optoelectronic devices can provide part of energy while ensuring high transparency,so that it can be used in intelligent window,new energy materials and other related fields.At present,the research in this field mainly focuses on the transparency of solar cells and photoelectric detectors.The main method is to improve the transparency of the device by choosing suitable materials and reducing the thickness of the absorber layer,and to find a balance between the transparency and the photoelectric conversion performance.The pn junction device has a simple structure and excellent photoelectric conversion performance,so it has a great potential in the field of transparent photoelectric devices.Cuprous oxide(Cu₂O),as an intrinsic p-type metal oxide semiconductor,has been widely used in the preparation of pn junction devices due to its abundant reserves,simple preparation,non-toxic and excellent photoelectric properties.The transparency of the pn junction device requires a thinner material film layer,so the quality of Cu₂O film and the matching process between the materials are very high requirements,which are also the problems to be solved before the practical application of Cu₂O transparent pn junction.Adding a transition layer is a simple and effective method,which can effectively improve the interface quality and level matching degree,and further balance the transparent-photoelectric conversion performance of the transparent pn junction.In this paper,Cu₂O as the main p-type material,through different methods to prepare films.SnO₂with a better energy band was selected as N-type layer,and the pn junction was constructed by Cu₂O and SnO₂films.Then,Cu O film and SnO₂quantum dot film are introduced as the transition layer to improve the photoelectric conversion efficiency of the pn junction with the guarantee of transparency.The specific research work is as follows:(1)Using the magnetron sputtering method,argon(Ar)was used as the working gas,and Cu₂O target was sputtered for 30min at different substrate temperatures to prepare Cu₂O thin films.At the same time,p-type Cu₂O thin films were deposited potentiostatic in a three-electrode system with copper sulfate and lactic acid solution as electrolyte by electrochemical deposition method.The properties of the samples were studied by SEM,XRD,UV-Vis and other methods.The results show that the crystallinity,electrical and optical properties of the films are affected by different substrate temperatures,and the thickness and surface morphology of the films vary greatly.By comprehensive comparison,the substrate temperature of 25?was selected as the preparation parameter of subsequent Cu₂O films.(2)The Cu₂O thin film was prepared by magnetron sputtering method,and then an extremely thin Cu O transition layer was produced on the surface of the Cu₂O thin film by simple thermal oxidation method.Finally,the SnO₂thin film was deposited by secondary sputtering to construct a transparent pn junction.The results show that the transmittance of the prepared device is up to 75%in the visible region.Compared with the sample without the transition layer,the photoelectric conversion performance of the prepared device is improved by about 450 times,and the stability is good.The main reason can be attributed to the existence of Cu O autooxidation transition layer,which makes the device obtain better energy level and lattice match,provides a good channel for carrier transmission,and Cu O can effectively prevent Cu₂O oxidation and increase stability.(3)The SnO₂film was prepared by sputtering method,and the SnO₂quantum dots(SnO₂QDS)prepared by chemical method was introduced by annealing.Then,Cu₂O films were deposited on the surface of SnO₂QDS/SnO₂films by secondary sputtering.The prepared transparent photoelectric device shows a high transmittance of about 80%under visible light.Compared with the unmodified device,the photoelectric conversion enhancement of about 1.1×10³times is presented,and it shows good stability during the cycle of 20000s.This phenomenon is mainly attributed to the fact that SnO₂QDs with high quantum efficiency and appropriate band structure can accelerate carrier injection,separation and migration,while its smaller size can improve the pn junction interface,thus improving the photoelectric conversion efficiency while ensuring transparency.