Inverted Perovskite Solar Cell Based By Magnetron Sputtering Doped Nickel Oxide Hole Transport Layer

In recent years,organic and inorganic hybrid perovskite Solar Cells have been widely concerned because of their excellent characteristics such as low temperature preparation,adjustable band gap and easy to fabricate.The photoelectric conversion efficiency has been rapidly increased from 3.8%to 25.7%,making it become the most promising photovoltaic devices.The hole transport layer has an important effect on the efficiency of perovskite solar cells.Inorganic hole transport layer is widely used in perovskite solar cells because of its high carrier mobility,high stability and low cost.As an inorganic hole transport material,nickel oxide has advantages such as high optical transmittance,good stability and simple preparation method.Nickel oxide hole transport layer is generally used in inverted perovskite solar cells.However,the power conversion efficiency of nickel oxide based perovskite solar cells is still lower than that of organic hole transport layer perovskite solar cells.The main reason is that the conductivity of nickel oxide film itself is not high.Normally,nickel oxide is fabricated by solution method,which causes non-uniform coverage of FTO substrate.In this case,this thesis adopts magnetron sputtering method to prepare nickel oxide hole transport layer because of the advantages of good crystallinity,high flatness,uniform surface and stability.In order to increase the conductivity of nickel oxide,co-sputtering is usually used,which needs higher requirements for experimental instrument stand the cost will also increase as well.In this thesis,we mainly focus on p-i-n perovskite solar cells based on nickel oxide hole transport layer.The Cu doped nickel oxide target was directly used for magnetron sputtering to achieve efficient doping of nickel oxide hole transport layers,which enhanced the hole transport ability and the efficiency of the perovskite solar cells.The specific content of this thesis can be concluded as follows:（1）The properties of NiOx films were efficiently improved by optimizing the sputtering pressure of magnetron sputtering process.We compared NiOx and Cu-NiOx films fabricated by the different sputtering pressures（1,3,5pa）in the working atmosphere of pure argon.Both NiOx and Cu-NiOx films were relatively uniform and compact with low surface roughness.By controlling the sputtering pressure,the ratio of Ni³⁺and Ni²⁺can be effectively adjusted.When the sputtering pressure was 1pa,both NiOx and Cu-NiOx film had the best conductivity.（2）Cu doping successfully increased the conductivity of NiOx hole transport layer.We directly doped the nickel oxide target by Cu and sputtered the Cu-NiOx target at room temperature.Compared with the undoped NiOx film,the conductivity of the Cu-doped NiOx film was significantly improved,which was related to the increase of the ratio of Ni³⁺/Ni²⁺in the NiOx film.（3）The FTO/NiOx/FA_0.75Cs_0.25pb(I_0.8Br_0.2)₃/C60/BCP/Ag inverted perovskite solar cells were prepared,and the influence of NiOx film sputtering pressure on the performance of the solar cells was studied.When the sputtering pressure was 1pa for both NiOx and Cu-NiOx films,the efficiency is optimal,which is mainly due to the high conductivity of the NiOx/Cu-NiOx film obtained under this sputtering pressure.Perovskite films grown on Cu-doped NiOx films had larger grain size and lower defect state density,which can effectively improve the carrier transport efficiency at the interface and the short-circuit current density of the solar cell,and ultimately significantly enhance the efficiency of the solar cells.When the sputtering pressure was 1pa,the highest power conversion efficiency of the Cu-doped NiOx film-based inverted perovskite cell could reach 15.34%.It can maintain 90.2%of the original efficiency after 20 days in the N₂ glove box,showing a good stability.