Studies On Close Spaced Sublimation Fabricated CdS Buffer Layer And Antimony Selenosulfide Thin Film Solar Cells

Antimony Selenosulfide（Sb₂（S,Se）₃）is a new type of inorganic compound semiconductor material of theⅤ-Ⅵgroup.It has received unprecedented attention attribute to its simple phase,high absorption coefficient(≈10⁵ cm^-1),adjustable band gap（1.1～1.75 e V）,stable physicochemical properties,and high earth abundance of the elements contained.In recent years,the photoelectric conversion efficiency of Sb₂（S,Se）₃ thin film solar cells has a fast improvement,but there is a significant gap between them and the Shockley Quieser limit efficiency value（>30%）.Further research is needed to improve their performance in order to meet commercial applications.In Sb₂（S,Se）₃ solar cell devices,the CdS electron transport layer plays a very important role in the contact of p-n junctions,which also influences greatly the separation and transmission of photon-induced carriers.In this paper,the preparation and research of the CdS electron transport layers are taken as the entry point to realize the enhanced performance of Sb₂（S,Se）₃ solar devices.Focusing on this research subject,the research results have been obtained in this thesis as follows:（1）An effective dual CdS electron transport layer is proposed for the first time to be applied to CdS/Sb₂（S,Se）₃ heterojunction contacts.The advantages of the close-space sublimation method and the chemical water bath method are combined.The CdS thin film prepared has the characteristics of high crystallinity,strong orientation,and high density,while avoiding the leakage phenomenon caused by the appearance of pinholes in the CdS thin film.Through the study and characterization of its surface morphology,its surface roughness（RMS）has been greatly improved.At the same time,high-quality Sb₂（S,Se）₃ thin films were obtained,and the corresponding device performance increased from 3.09%to 6.94%.（2）The deposition of CdS electron transport layers by near space sublimation method and its application in Sb₂（S,Se）₃ solar cells were investigated in depth.The mechanism of the deposition process of CdS thin films was described in detail.High crystalline CdS thin films were obtained by adjusting the thermal field pressure,evaporation source,and substrate temperature.This can induce and improve the oriented growth of the Sb₂（S,Se）₃ absorption layer,enhance the carrier transport rate,and reduce defects in the absorption layer.After optimization,the PCE of 7.12%was acquired of the Sb₂（S,Se）₃ device,achieving the full vacuum process for the preparation of Sb₂（S,Se）₃ thin film photovoltaic devices,which provides a certain reference significance for the continuous production of inorganic solar cells.（3）Deep level defects in Sb₂（S,Se）₃ thin film photovoltaic devices equipped with CdS electron transport layers that manufactured by close-space sublimation as well as chemical bath deposition methods were studied and compared by variable temperature admittance method.The quantitative analysis of defects is carried out from the parameters such as defect density,defect activation energy,capture cross-section and capture time,and its mechanism is described,which provides certain guiding significance for the improvement of defects.