| Energy is an important driving force for the rapid development of modern society.At present,we still mainly rely on the traditional fossil energy as the basic guarantee for human survival.With science and technology continue to progress and develop,the increasing energy burden inevitably brings fossil energy exhaustion and serious environmental pollution.In order to realize the coexistence of mankind and nature,as soon as respond to the national policy of "peak carbon dioxide emissions" and"carbon neutrality",it is urgent to develop clean energy that can replace fossil fuels.Solar energy has been applied widely because it is not limited by reserves and geographical location,energy conservation and environmental protection.Power generation technology based on photovoltaic effect is one of the typical applications of solar energy,photovoltaic cells have developed from the first generation of traditional silicon based solar cells to the current third generation of new photovoltaic devices.Perovskite solar cells,as the leader of new devices,have attracted the attention of many researchers in recent years.Such devices has simple preparation process and the highest photoelectric conversion efficiency has reached 25.7%,which exceeds the traditional silicon based solar cells.However,one of the main problems restricting its development is charge transfer and its stability.In this paper,mesoscopic perovskite solar cells are mainly studied.Titanium dioxide（TiO2）as the electron transfer material,the effective charge transfer between the photoactive layer（perovskite）is an important factor affecting the performance of the cell.Therefore,TiO2 surface modification or rare earth doping was carried out to investigate the influence of the change of crystal structure,surface defect and energy level change on the interface electron transport of TiO2/perovskite film and crystal type growth of perovskite film in this paper,then the performance and stability of device are regulated.The specific work contents and conclusions are as follows:（1）The photoactive layer of PSCs was prepared by two-step method and anti-solvent method respectively,and the PCE of PSCs was tested.The repeatability test showed that the anti-solvent method is more conducive to the preparation of high-quality perovskite layer,which is helpful to improve the PCE of PSCs.（2）Pure tetragonal anatase TiO2 nanoparticles were synthesized by one-step hydrothermal method as electron transport layer（ETL）in perovskite solar cells,and compared with commercial Dyesol-18-NRT TiO2.The experimental results show that the PCE of self-synthesized TiO2 as a mesoporous layer can reach 15.24%,but there is still a certain gap in efficiency compared with commercial TiO2（16.68%）,which is mainly due to the poor charge transfer and transport capability at the interface between self-synthesized TiO2 and perovskite layer due to the existence of surface defects.（3）Based on the above problems,the surface treatment of self-synthesized TiO2 was carried out in order to passivate TiO2 crystal plane defects and improve the interface charge transfer of TiO2/perovskite and the internal electron transfer of TiO2 in this paper.During the preparation of TiO2 by hydrothermal method,appropriate amount of acetic acid was firstly added,and a certain concentration of sulfuric acid aqueous solution（H2SO4）was used for secondary hydrothermal treatment of the nanoparticles obtained.Compared with the unmodified sample,the surface defects of the modified TiO2 were effectively passive,the exposure ratio of {101} crystal plane increased,and-SO3-1 group was introduced on the surface could promote the charge transfer capacity of mesoporous TiO2/perovskite interface,reduce the electron-hole recombination probability,and optimize the crystal growth conditions of perovskite film.Finally,the PCE of perovskite solar cells increased from 15.24%to 20.27%,which retarded the hysteresis effect of the cells,and improved the stability and repeatability of devices.（4）Neodymium-doped anatase TiO2 nanoparticles（Nd-TiO2）were prepared by solvothermal and used as ETL in perovskite solar cells in order to improve the charge transfer ability at the interface.The experimental results show that Neodymium-doped TiO2 can reduce the energy gap between the photoactive layer and ETL,which is more conducive to the interface charge transfer.The open-circuit voltage of the device is increased from 1.02 V to 1.13 V Meanwhile,the density of the defect states of TiO2 is reduced and the electron mobility is increased from 0.92×10-8 cm2·v-1·s-1 to 2.52×10-8 cm2·v-1·s-1.,and the final PCE is up to 20.95%,and the stability of perovskite solar cells are effectively improved. |
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