Research On Interface And Additives In Perovskite Solar Cells

In recent years,the power conversion efficiency of the organic-inorganic hybrid perovskite solar cell has been rapidly improved from 3.8%to 22.7%,demonstrating great potential in low-cost solar cells and other optoelectronic devices.The success is mainly attributed to large optical absorption coefficient,long range carrier diffusion,high charge mobility,bipolar transport,tunable level energy,and extremely low trap-state etc.At present,the key hurdles restricting its commercial development are mainly caused by low power conversion efficiency,poor stability and high device preparation cost.In order to solve these problems,we adopted a few strategies to improve the quality of perovskite absorber films.For example,composition optimization of the perovskite materials,development of suitable interface materials,and device preparation process.In this thesis,we explored excellent interface materials and developed inexpensive additives to optimize the quality of perovskite absorber to enhance its efficiency and stability.The main results of the dissertation are summarized as follows.(1)We innovatively incorporate high-mobility carbon materials(graphene oxide)into the PEDOT:PSS,and PEDOT:PSS thin films with different GO doping concentrations were prepared on ITO glass via solution spin-coating.The results showed that 500 uL GO-doped PEDOT:PSS thin films exhibited the best surface coverage,low roughness and high light transmittance.In addition,the mobility of 500 uL GO-doped PEDOT:PSS thin films was improved to 1.57 × 10-4 cm2 V-1 s-1,which was an order of magnitude higher than that of original PEDOT:PSS thin films(5.55 X 10-5 cm2 V-1 s-1).(2)Inverted perovskite solar cells were successfully prepared using GO-doped PEDOT:PSS thin film as hole transport layers.Compared with the control devices without GO-doped,the leakage current was significantly reduced,leading to higher open circuit voltage and the power conversion efficiency.The study found that higher transmittance and hole mobility of the GO-doped PEDOT:PSS thin film,which can quickly collect and extract holes from the perovskite absorption layer and reduce the charge recombination,thus increasing the short circuit current and fill factor.(3)We first used 1,8-octanedithiol as an efficient additive for FA0.95 Cs0.05 PbI3 perovskite.By optimizing the concentration of 1,8-octanedithiol,we prepared perovskite films with high crystallinity,lower surface roughness,larger grain size,lower electron trap densities and longer carrier lifetimes using 3%1,8-octanedithiol as an additive.It is found that 1,8-octanedithiol would coordinate with lead to form the chelate-Pb compound,leading to smaller Gibbs free energy during perovskite crystallization process,facilitating formation of high-quality perovskite films.Based on these results,we successfully fabricated planar perovskite solar cells,which increased the efficiency to 19.36%compared to the control device(18.39%).The improvement of performance is mainly due to the perfection of the quality of the perovskite film after addition of 3%1,8-octanedithiol,the higher crystallinity and the larger grain size can effectively reduce the defect density and charge recombination in the film,Finally,a higher performance of planar perovskite solar cells is obtained with reduced J-V hysteresis.