Study On The Influence Of Inhibition Of Li~+ Migration On The Performance Of Perovskite Solar Cells

The perovskite solar cell based on organic-inorganic hybrid perovskite material has been widely concerned by the scientific and industrial field,since it has realized a high power conversion efficiency of 25.8%.However,stability of perovskite solar cell is an crucial factor restricting its commercialization.The one of most widely used hole transport materialsinperovskitesolarcellis2,2’,7,7’-tetrakis（N,N-di-p-methoxyphenylamine）-9,9’-spirobifluorene（Spiro-OMe TAD）.Lithium bis（trifluoromethanesulfonyl）imide（Li-TFSI）and 4-tert-butylpyridine（t BP）are often used as dopants for Spiro-OMe TAD to boost their hole migration properties.Although Li-TFSI can improve the hole transport performance of Spiro-OMe TAD,the Li⁺in Spiro-OMe TAD can migrate to the perovskite layer and the electron transport layer easily,which severely reduces the stability of the perovskite solar cell.Therefore,it is significant to study the Li⁺migration behavior at the interface of perovskite/hole transport layer and explore effective methods to suppress Li⁺migration for improving the stability of perovskite solar cell.In this thesis,functionalized ionic liquids andβ-diketone were used as the surface modification agents to inhibit the migration of Li⁺and improve the performance of perovskite solar cell.The main research contents are as follows:（1）The 1-butyl-3-methyl imidazolium phosphate dibutyl ester（[BMim]⁺[DBP]^-）ionic liquid（IL）was designed and synthesized for the modification of perovskite/Spiro-OMe TAD interface in perovskite solar cell.The coordination interaction between-P=O in[BMim]⁺[DBP]^-IL and Li⁺can inhibit the migration of Li⁺and improve the device stability.The[BMim]⁺[DBP]^-IL can also accelerate the carrier extraction efficiency of the perovskite/Spiro-OMe TAD interface by regulating the energy level matching.Under 100m W cm^-2（AM 1.5 G）illumination,the power conversion efficiency of the device based on[BMim]⁺[DBP]^-IL interface modification was 21.16%,which was better than that of the control device（19.31%）.The stability of the target device is better than that of the control device under the aging conditions of relative humidity 50-60%and 60℃.（2）Thiophenyltrifluoroacetone（TTA）is used to modify the perovskite/Spiro-OMe TAD interface in perovskite solar cells.Theβ-dione structure of TTA can coordinate with Li⁺and form stable chelate structure,which can improve the migration barrier of Li⁺and inhibit the migration of Li⁺.At the same time,carbonyl（-C=O）and thiophenyl groups in TTA can anchor to Pb²⁺in perovskite and form-C=O---H and-F---H hydrogen bonds,which can effectively decrease the defect state density and the associated non-radiative recombination,and promote the charge transport at the interface between perovskite and Spiro-OMe TAD.The TTA-modified device has a power conversion efficiency of more than 22%.Under the aging conditions of 60℃and relative humidity of50-60%,TTA modified devices exihibits the better stability than that of devices without TTA.