Study On Defect Passivation Of Perovskite Layer Of Perovskite Solar Cells With Multi-size Nanofibers

The efficiency of perovskite solar cells depends on the recombination process of light-excited charge carriers.When the defects in the perovskite film form deep-level traps,they only capture electrons or holes,and these electrons or holes cannot pass through the electron-vacancy of the deep-level trap described by the Shockley-Read-Hall theory.Hole-elctron reorganization is considered to be the main way to cause loss.In this study,a simple electro spinning technique was used to prepare carbon nanofibers with multiple size distributions and loaded with abundant nitrogen-containing functional groups.The carbon nanofibers rich in nitrogen provides many nucleation sites for the crystallization of the perovskite,and the nitrogen-based functional group contained on the carbon nanofibers can be combined with the form of a Lewis base.Coordination with uncoordinated lead ions or lead clusters to form Lewis adducts.The formation of such adducts can reduce non-radiative charge recombination,extend carrier lifetime,and improve the performance and stability of perovskite devices.The main content of this research is as follows:First,by experimenting and exploring the parameters that affect electrospinning,a series of carbon nanofibers with gradient sizes were finally obtained.Subsequently,through a series of tests and characterizations,it can be observed that the carbon nanofibers has a good morphology and uniform size;infrared spectroscopy and EDX analysis show that carbon nanofibers have abundant nitrogen-containing functional groups and uniform element distribution.The degree of graphitization of carbon nanofibers is analyzed by Raman confocal spectroscopy.Then,the perovskite films doped with carbon nanofibers were prepared by a two-step method,and prepared into cell devices.XRD,XPS,FTIR tests and analysis show that the doped carbon fibers provide many nucleation sites for the crystallization of perovskite,and coordinate with lead ions or lead clusters to form Lewis adducts,and promote the crystallization of perovskite;the photoelectric conversion efficiency test shows that PCE of perovskite solar cells doped with carbon nanofibers reaches 20.22%,while PCE of cell device without carbon nanofibers doped is only 19.20%;durability and stability tests show that perovskite solar cell devices doped with carbon nanofibers show that PCE attenuation is smaller and the water and oxygen resistance is better.In general,the passivation of carbon nanofibers to the defects of the perovskite film not only improves its energy conversion efficiency,but also enhances its efficiency stability and resistance to water and oxygen.Finally,perovskite films containing electrospun carbon nano fibers with different size distributions was prepared.Test characterization showed that carbon nanofibers with different size distributions crystallize perovskite films all have a passivation effect,and different carbon fiber sizes have different passivation effects on the defect of the perovskite film.Because of their different sizes,the number of carbon fibers under the same quality is very different,so different sizes carbon fiber has a different optimal doping concentration;the defect state density test analysis shows that cell devices doped with finer carbon nanofibers have lower defect state density.In this paper,electrospun nanofibers are effectively applied to the defect passivation of perovskite layer,and have achieved higher parameters than standard devices.This is a new technical application that effectively solves the problem of perovskite solar cells.The defects of the photosensitive layer of the cell and the poor stability have promoted the practical application.