Study On Preparation Of Metal Cation Co-doped Titanium Dioxide And Co-evaporated All-inorganic Perovskite Films

In recent years,perovskite materials have attracted extensive attention of photovoltaic researchers due to their excellent properties such as adjustable band gap,long carrier diffusion length and low exciton binding energy.In just ten years,the photoelectric conversion efficiency of perovskite solar cells has reached more than 23%,which is considered to be the most likely new type of solar cells to replace monocrystalline silicon.In the current perovskite solar cells,both the electron transport layer and the perovskite absorption layer play an extremely important role.The former mainly transmits electrons and blockades holes,while the latter mainly absorbs sunlight and generates photogenerated electrons and holes.Therefore,the selection and control of the materials for the two layers are very important.For the electronic transport layer,the common choice is the titanium dioxide,which is good conductivity,stable and inexpensive.However,the preparation of titanium dioxide requires high temperature treatment,which hinders its application in flexible equipment,the conductivity and band of titanium dioxide need to be further optimized.These problems seriously hinder the commercialization of perovskite solar cells.In addition,the instability of organic/inorganic hybrid perovskite materials has also been troubling people,especially the low tolerance of organic components to temperature and humidity,which easily destroys the structure of materials when placed in the air,resulting in poor stability of the devices.Based on the above problems,we have done the following work:1.Niobium(Nb)and tantalum(Ta)ions were co-doped into the lattice of titanium dioxide by low temperature chemical bath method,and high quality doped titanium dioxide thin films were prepared.By adjusting the doping ratio of Nb and Ta ions,the conduction bottom of titanium dioxide can be moved up,which matched well with the energy band of perovskite layer and made charge transfer better.It is also found that the short-circuit current of the device can be effectively increased by adding Nb ions,and the open-circuit voltage of the cell can be increased by adding Ta ions.Optimizing the ratio of the two can achieve a good balance between the short-circuit current and the open-circuit voltage,thus improving the efficiency of the perovskite solar cell.Finally,0.5%Ta-0.5%Nb-TiO2 perovskite solar cells achieved 19.44%efficiency,10.5%higher than pure titanium dioxide devices,and its stability was also significantly improved.The perovskite solar cells kept about 90%of the initial value in the air for 500 hours,which was significantly better than pure titanium dioxide devices.2.The CsBr and PbBr2 materials were co-deposited on the substrates by co-evaporation technology to form dense CsPbBr3 perovskite films.The thickness and thermal annealing temperature of the films were optimized by a series of characterization methods such as XRD and absorption spectroscopy,and high quality perovskite films were obtained.Finally,perovskite solar cell devices with FTO/TiO2/CsPbBr3/Spiro-OMeTAD/Au structure were prepared.The photoelectric conversion efficiency of the device prepared by evaporation is 9.43%,which is nearly 50%higher than that of the perovskite device prepared by spin coating.At the same time,the stability of the device is also greatly improved.When the device is placed for 500 hours under the condition of 40%humidity,it is found that the efficiency of the device is still around 95%of the initial value.