Research On Defect Passivation Of Perovskite Solar Cells By Additive And Surface-treatment

In recent years,perovskite solar cells（PSCs）have attracted the attention of many scientific researchers due to their simple preparation process,low preparation cost,and high power conversion efficiency（PCE）.The quality of perovskite thin films plays an important role in the performance of PSCs,and the higher crystallinity,larger size and denser and smoother perovskite films mean higher PCE.Generally,the methods of perovskite thin films preparation can be divided into solution method and vacuum evaporation method.As one of the methods for the preparation of perovskite films by solution,the antisolvent-assisted one-step spin coating method has become the main choice for the laboratory with the advantages of simple and easy to obtain high quality films.However,during the crystallization process of perovskite,defects will occur at the interface and inside of the perovskite films,causing non-radiative recombination of carriers,and reducing the PCE of PCSs.Meanwhile,the defects are also the invasion sources of water and oxygen,resulting in the rapid degradation of the perovskite grains,and then reducing the stability of the devices.Surface passivation atop perovskite films and additive engineering is a proven significant strategy to reduce non-radiation recombination and improve interface contact.Therefore,it is an effective means to improve the performance of PSCs by suppressing the or passivating the defects of perovskite films.In this paper,we investigate the effects of anti-solvent drop addition time,volume and annealing temperature,time on perovskite films based on n-i-p type planar structure PSCs.Based on the results,a reasonable PSCs preparation process has been developed.The optimal preparation process for perovskite films by spin coating the 1.25 M perovskite precursor solution for 40μL on the clear substrate at 1000 rpm for 3 s and 4000 rpm for 30 s.In the first10 s of the second stage,the films were treated with 200μL of chlorobenzene and annealed at100℃for 10 min.The PSCs with FTO/Ti O₂/MAPb I₃/Spiro-OMe TAD/Ag structure can obtained average open-circuit voltage of 1.041 V,a short-circuit current density of 22.17m A/cm²,a fill factor of 61.17%and measured PCE is 14.12%.Secondly,a high-quality perovskite films was obtained by using glycerol as a perovskite precursor additive,which exhibits larger grain size,fewer grain boundaries,enhanced optical properties and reduced defect densities.More importantly,after optimizing the additive concentration of glycerol,the PSCs exhibited enhanced photovoltaic performance.Finally,we achieve a champion PSCs,with an open-circuit voltage of 1.093 V,a short-circuit current density of 23.14 m A/cm²,a fill factor of 66.59%and a PCE of 16.84%.Finally,we introduced Eu-OA to passivate uncoordinated Pb²⁺and I^-on the surface of perovskite film through coordination bonding by C=O and Eu³⁺.The introduction of Eu-OA can decrease the traps density of perovskite film,and reduce the nonradiative of carriers,without affecting the surface morphology of perovskite film.A champion PSCs with an open-circuit voltage of 1.044 V,a short-circuit current density of 22.70 m A/cm²,a fill factor of 67.77%and a PCE of 16.06%was obtained by optimizing the additive concentration of Eu-OA.