Research On Additive And Interface Engineering To Improve Performance Of Quasi-two-dimensional Perovskite Solar Cells

Organic-inorganic hybrid metal halide perovskite materials have attracted widespread attention from researchers due to their high light absorption coefficient,long carrier diffusion length,directly tunable optical bandgap,and excellent bipolar transport properties.After more than a decade of rapid development,the power conversion efficiency（PCE）of perovskite solar cells（PSCs）has increased from an initial value of 3.8%to 25.7%.However,the inherent instability of 3D perovskite solar cells to moisture,light,and heat has hindered their commercialization.In contrast,quasi-2D perovskite solar cells have better stability because the inorganic layers are separated by large-volume hydrophobic cations.However,the large volume cations as spacers are electrically insulating,which affects the carrier transport and reduces the efficiency of quasi-2D perovskite solar cells.In addition,quasi-2D perovskite films prepared by solution methods have poor crystallinity,and there are many defect states at grain boundaries and on the surface of the film,which is also an important factor affecting the performance of quasi-2D perovskite solar cells.In order to improve the performance of quasi-2D perovskite solar cells,various methods have been employed,such as thermal spin-coating,designing suitable interlayer cations,additive engineering,and interface engineering.Among them,additive engineering and interface engineering are two widely used and effective methods.Additive engineering involves introducing additive molecules into the perovskite precursor solution,which can control the crystallization process of the perovskite during film formation,improve the crystallinity of the perovskite,enlarge the grain size,and passivate grain boundary defects,enhancing the extraction and transport efficiency of charge carriers,thereby improving the performance of quasi-2D perovskite solar cells.Post-treatment is a process of interface engineering,in which a solution containing interface modifying material is spin-coated onto the perovskite film after film formation,followed by annealing.Post-treatment can promote secondary crystallization of the perovskite,interconnect and fuse the grains,and passivate surface defects,reducing the recombination of photogenerated charge carriers,thereby improving the performance of quasi-2D perovskite solar cells.Therefore,this paper prepared solar cells based on quasi-2D ACI-type perovskite GAMA₅Pb₅I₁₆,using additive and post-treatment methods to improve the crystallinity and film quality of the perovskite film,reduce grain boundary and surface defects,and enhance the performance and stability of perovskite solar cells.The specific contents of the paper are as follows:（1）The conductive molecule material 2,7-Bis（diphenylphosphoryl）-9,9’-spirobifluorene（SPPO13）was added to the precursor solution of the perovskite solar cell GAMA₅Pb₅I₁₆to prepare the perovskite solar cell.The experiment showed that the SPPO13 molecule passivated the uncoordinated lead ion defects in the perovskite layer through the P=O bond,effectively reducing the defect states on the grain boundary surface,improving the crystalline quality of the film,reducing the recombination of photogenerated carriers,and increasing the conductivity of the perovskite film.After optimization,the introduction of the additive SPPO13 increased the conversion efficiency of the perovskite solar cell to 18.46%,which was significantly higher than that of the cell without SPPO13（16.98%）.In addition,SPPO13 improved the stability of the perovskite solar cell.After being stored in air for 30 days,the conversion efficiency of the solar cell with SPPO13 remained at 90%of its original value.This study provides a new approach to improve the charge transfer characteristics and performance and stability of quasi-2D perovskite solar cells by using organic conductive molecular materials.（2）The surface of perovskite GAMA₅Pb₅I₁₆film was post-treated using an isopropanol（IPA）solution of 4-Acetamidophenol（APAP）to prepare a perovskite solar cell.The researchers found that APAP post-treatment regulated the secondary crystallization of the perovskite film,making the perovskite grains larger,the film more dense and smooth,and passivated the surface defect states of the perovskite film,reducing carrier recombination and thus improving the efficiency of the perovskite solar cells and mitigating the hysteresis effect of the cells.After optimization,the conversion efficiency of the perovskite solar cells based on APAP post-treatment was increased from 16.72%of the control group to 18.01%.In addition,APAP post-treatment enhanced the water and oxygen resistance of the perovskite film,improving the stability of the quasi-2D perovskite solar cells.This study demonstrates that APAP annealing is an effective strategy to passivate the defects of the perovskite,providing a feasible method for achieving high-performance quasi-2D perovskite solar cells.