Research On Interface Modification Of Perovskite Solar Cell Using Hole Transport Materials

Through more than ten years of rapid development,the certified power conversion efficiency(PCE)of perovskite solar cells(PSCs)has reached up to 25.5%,which has broad development prospects.However,there is a large number of defects in the polycrystalline perovskite film prepared by the solution method,especially at the grain boundaries and surface,which reduce the performance and long-term stability of the device.In addition,for the formal-structure PSCs,there is still a large energy loss at the interface between the perovskite and the hole transport layer(HTL).In order to solve the above problems,functional materials are added to the anti-solvent to modify the perovskite/HTL interface,thereby passivating the defects at grain boundaries and surface,reducing the energy barrier between the interface,and thus improving the charge collection efficiency.As a result,the device performance and long-term stability can be significantly improved.In this thesis,we have studied the effect of hole transport materials as additives in the anti-solvent on the performance of PSCs.The specific work content is as follows:(1)The interface at the perovskite/HTL layer is optimized by adding p-type conjugated polymerpoly[[4,8-bis[(2-ethylhexyl)oxo]benzo[1,2-b:4,5-b']dithiophene-2,6-Diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl]](PTB7).The results of the research show that the defects of the perovskite films are effectively passivated by PTB7.The quality of the perovskite film is improved and the defect density in the perovskite film is clearly reduced.PTB7 can also reduce the energy barrier between the perovskite and the hole transport layer,which is beneficial to reduce the charge recombination at the interface and thus improve the charge collection efficiency.The PCE of the device optimized by PTB7 is increased from 17.26% to 18.93%.At the same time,PTB7 can inhibit the migration of iodine ions inside the device,thus the current density-voltage(J-V)hysteresis effect of the device is smaller than that in the control one.In addition,the polymer PTB7 can form a hydrophobic protective layer on the surface of the perovskite film,which enhances the water and oxygen resistance of the PSCs.The device modified by PTB7 can maintain more than 80% of the initial efficiency after being placed at room temperature for 30 days.(2)The high-quality perovskite films with interface modification are realized by adding conjugated p-type small molecular 4,4'-cyclohexylbis[N,N-bis(4-methylphenyl)aniline](TAPC)in the anti-solvent.The research results show that the triphenylamine group in the TAPC can interact with the lead ions in the perovskite precursor solution,thereby regulating the crystallization process of the perovskite film.The prepared perovskite film has a larger grain size and higher crystallinity.In addition,TAPC can effectively passivate the defects on the grain boundaries and surface of the perovskite film,thus reducing the defect state density of the film and improving the charge collection efficiency.As a result,the PCE of the device optimized by TAPC is increased from 18.37% to 20.67%.In addition,since the TAPC organic molecules can increase the hydrophobicity of the perovskite film,the prepared device shows an improved air stability,which maintains more than 80% of the initial PCE after storing for 30 days.