Study On The Influence Of Hole Transport Materials On Stability And Performance Of Perovskite Solar Cells

In recent years,perovskite solar cells（PSCs）have attracted widespread attention.PSCs have advantages such as high molar extinction coefficient,high open circuit voltage,simple structure,and low cost.However,the problems of device stability and large-area production of PSCs are the main obstacle that hinders their commercial production.Solving these problems requires research on various aspects such as device structures and materials.Common planar structured devices are unstable due to the use of Spiro-OMeTAD（Spiro）.In this thesis,polymer poly（3-hexylthiophene-2,5-diyl）（P3HT）was used to replace Spiro,and we studied its effect on the performance and stability of planar devices.Since inverted perovskite solar cells are generally considered to be more stable,we then employed a new hole transport material,10-（4-（4,6-diphenyl-1,3,5-triazin-2-yl）phenyl）-9,9-dimethyl-9,10-dihydroacridine（DMAC-TRZ）and inorganic NiO_x for the inverted devices.Through UV-Visible absorption spectroscopy,scanning electron microscopy,atomic force microscopy,X-ray diffraction analysis,steady-state photoluminescence spectroscopy,electrochemical workstations and J-V testing,we conducted the following research:（1）Optimized the performance of the planar perovskite solar cells based on P3HT,and studied the phenomenon that the efficiency increased a lot at the beginning a few days.Through a series of comparative experiments,it is found that the water on the interface of P3HT/perovskite induces this phenomenon.Doping Li-TFSI in P3HT improved the performance of the devices and reached a conversion efficiency of17.55%.The stability of the devices based on P3HT was also tested.It was found that P3HT can protect the perovskite well and make the devices have good long-term stability.The devices based on undoped P3HT were placed under 30%humidity and25°C and it can still maintain more than 75%of the initial efficiency after one year.Li-TFSI is hygroscopic,which improves performance but reduces stability.（2）A new type of organic small molecular material DMAC-TRZ was introduced as a hole transporting material in inverted perovskite solar cells and the optical,electrical and chemical properties of DMAC-TRZ were characterized.DMAC-TRZ was found to have the best effect when annealed at 200°C.Its conductivity and corresponding performance were superior to those of other temperature-annealed films.At the same time,the film thickness of DMAC-TRZ was optimized,and a device with a conversion efficiency of 11.90%was fabricated.In addition to efficiency,we also researched the illumination,thermal and long-term stability of the devices.The thermal stability of the device was limited due to poor thermal stability of MAPbI₃ in the perovskite.In addition,it was found that the devices fabricated by DMAC-TRZ decreased after continuous illumination.（3）Study on the effect of NiO_x hole transport layer on the performance and stability of inverted perovskite solar cells.In order to improve stability,NiO_x is used as a hole transport layer.We synthesized NiO_x through two different ways.By comparison,it was found that the hole transport layer fabricated by NiOx nanoparticles had better performance.The efficiency and stability of the devices were better than those prepared by the solution method.The optimum efficiencies of the devices prepared by the two methods were 14.71%and 12.91%,respectively.The devices prepared by the two methods exhibit excellent stability.They had good long-term stability and thermal stability.The devices can maintain more than 80%of the initial efficiency under 25°C and 30%relative humidity for 1000 h,and they have good thermal stability when heating at 50°C.