Effect Of Additives On Performance Of Perovskite Solar Cells

In recent years,perovskite solar cells（PSCs）have become a research focus due to their excellent photovoltaic performance.The power conversion efficiency（PCE）of PSCs has increased from 3.8%to 25.7%,which is a milestone progress.The preparation process of perovskite films is mainly based on solution-based film deposition techniques,including one-step and two-step methods.However,it is difficult to control the morphology of the perovskite films prepared by the one-step method involving anti-solvent,these films have low film coverage and contain a large number of defects at the surface and grain boundaries.The two-step method allows better control of the morphology of perovskite films.Firstly,lead iodide（Pb I₂）film is prepared,and then the organic halide solution is spin-coated on it.The organic halide solution diffuses in film and reacts with Pb I₂ to form perovskite.The morphology of the Pb I₂ film plays a decisive role in such diffusion.To solve these issues,this paper introduces additives into the Pb I₂ precursor solution to control the morphology of the Pb I₂ film,thus reducing film defects,promoting carrier transport and obtaining high-performance perovskite solar cells.The research contents are as follows:1.In the process of preparing perovskite films by the two-step method,Pb I₂ and organic halides need to react sufficiently to form perovskite,and the reaction efficiency largely depends on the morphology of the Pb I₂ film.If the Pb I₂ film is too dense,it will hinder the diffusion of organic halides in the planar heterojunction,thereby reducing the reaction efficiency.To solve this problem,we introduce acetone as a morphology regulator for the Pb I₂ film.The addition of acetone weakens the interaction between DMSO and Pb I₂,thereby forming a more suitable Pb I₂ film morphology.Pb I₂ can react with organic halides more effectively,resulting in the conversion to high quality perovskite films.The FA_1-xMA_xPb I₃ perovskite film prepared by this method has lower defect density.PSCs containing 1%acetone can provide a PCE of 22.07%,which indicates that optimizing the morphology of the Pb I₂ film can greatly improve the device performance.This work is of great significance for achieving efficient and low-cost solar cells.2.Additives can modulate the morphology of Pb I₂ films,which in turn affects the quality of the perovskite films,we propose an additive strategy and apply it to the two-step method for preparing perovskite films.Specifically,we add acetonitrile（ACN）to the Pb I₂ precursor solution to control its morphology.Due to the low boiling point of ACN,it evaporates faster than dimethyl sulfoxide（DMSO）and N,N-dimethylformamide（DMF）during the annealing process of the Pb I₂ film,leaving pores which facilitate the diffusion of organic halides and improve the conversion efficiency of Pb I₂ to perovskite.Therefore,the high-quality perovskite films with enhanced light absorption and reduced defect density are obtained.Compared with PSCs without ACN,PSCs with 1.2%ACN showed a significant improvement in PCE from 19.77%to21.79%.This simple and easy-to-use method provides a new approach for the commercialization of PSCs.