Interface Regulation Of Tin Halide Perovskite Solar Cells

Perovskite Solar Cells(PSCs),one of the most promising photovoltaic devices,have been developing rapidly in recent years with the soaring power conversion efficiencies(PCE).However,the ecological impact caused by their toxicity cannot be ignored and is becoming an obstacle to their large-scale commercial production.Tinbased PSCs(TPSCs)have been widely investigated in this regard due to their desirable band gap structure and optical properties.However,the rapid crystallization rate of tin halide perovskites creates high defect density and tin vacancies,thus accelerating the non-radiative recombination at the interface.Therefore,it is particularly critical to investigate the photoexcited charge carriers dynamics in TPSCs.Well-designed interface can finely optimize the energy level alignment of the device,passivate trap defects and reduce the open-circuit voltage loss at the interface.In this thesis,the photovoltaic performance and stability of p-i-n TPSCs were enhanced through interfacial engineering.A systematic and in-depth characterization analysis of perovskite films,carrier transport layers and devices has been carried out.(1)Post-treatment of tin-based perovskite layers with 3-(trifluoromethyl)phenylethylamine hydriodide(CF3PEAI)passivated negatively charged defects and density of states in the perovskite layers,resulting in high-quality perovskite films with reduced lattice micro strain.It was also confirmed that the posttreatment inhibited trap-assisted non-radiative recombination at the interface between the perovskite films and electron transport layers,with more effective charge dissociation and greater electron mobility,resulting in an increase of PCE to 10.35%.The device retained 70% of its original PCE after 150 hours under 15% relative humidity.(2)Ammonium acetate doping of the hole transport layer was used to promote the extraction and transmission of hole transport at the interface.The study showed that the doping not only improved the conductivity and light transmission of the hole transport layer,resulting in faster extraction of holes and less hindrance,but also enhanced the quality of the tin-based perovskite films,lowered the dielectric constant and decreased non-radiative recombination,resulting in an increase of the PCE from 8.25% to 9.39%.(3)The addition of the 2-bromoethylamine hydrobromide buffer layer at the bottom of the perovskite layer was able to effectively passivate the defects associated with charge trapping in the hole transport layer,thus increasing its conductivity with no negative effect on transparency.At the same time,the film quality of the perovskite layer was improved,residual stresses were reduced,and charge collection efficiency was increased.The PCE of the modified TPSCs devices increased from 8.28% to 9.50%.Based on the above study,the interfacial modulation of tin-based perovskites in pi-n TPSCs reduces the lattice micro strain and trap density on the surface of perovskite films,as well as the defect states and non-radiative recombination at the interface,providing a new way to elevate the PCE of TPSCs.