Study On The Regularity Of Hole Transport Materials Oxidized By Phospho-molybdenum-vanadium Heteropoly Acids And The Photoelectric Properties Of PSCs

As a new type of photoelectric conversion equipment,perovskite solar cells(PSCs)have attracted widespread attention.In the structure of PSCs,the hole transport material(HTM)is mainly responsible for the extraction and transport of holes.Spiro-OMe TAD is currently a commonly used HTM material.Due to the disvantages of its poor conductivity and requiring uncontrollable oxidation in the air for a long time.Chemical doping is usually required to improve the performance of HTM to prepare efficient and stable PSCs.Aiming at the inherent defects of Spiro-OMe TAD,this paper intends to select Keggin-type phosphomolybdic acid and three kinds of vanadium substituted polyoxometalates for the chemical doping of HTM.Utilizing polyoxometalates(POMs)with excellent oxidation ability and conductivity for the improvement of conductivity and hole mobility of HTM through the oxidation of POMs on Spiro-OMe TAD,thus improving the photoelectric performance of PSCs.At the same time,exploring the influence of different vanadium substitution numbers on the performance of PSCs.Based on the excellent oxidation ability of Keggin-type POMs,H₃PMo₁₂O₄₀(PMo₁₂)is used as a p-type dopant for the chemical doping of HTM film.PMo₁₂ can replace the uncontrollable air oxidation process and directly oxidize Spiro-OMe TAD under inert condition.Electrochemical tests were carried out to analyze the changes in the conductivity of the HTM film and battery performance before and after doping.It was found that the introduction of PMo₁₂ increased the conductivity and hole mobility of the HTM film,and the photoelectric conversion efficiency(PCE)of the PSCs increased from 19.37%of the blank device to 20.00%.By introducing vanadium atoms with stronger oxidation ability into the PMo₁₂structure,three types of vanadium-substituted Keggin POMs H₄PMo₁₁VO₄₀(PMo₁₁V),H₅PMo₁₀V₂O₄₀(PMo₁₀V₂),H₆PMo₉V₃O₄₀(PMo₉V₃)were synthesized and used for the chemical doping of HTM.Through the electrochemical test of the films,it was found that as the number of vanadium substitutions increases,the oxidation ability of the compounds also increases,which further improves the conductivity and hole mobility of the HTM films.The internal oxidation law was studied by X-ray photoelectron spectroscopy(XPS),and the structure-activity relationship between the POM structure and battery efficiency was studied.The effect of different vanadium substituted POMs on the charge transport of HTM was further revealed through the fluorescence lifetime,EIS,transient tests and other characterization methods.Finally,benefiting from the promotion of hole extraction and energy level matching by POMs,the PCE of the three vanadium-substituted POMs modified PSCs devices increased from 19.41%of the blank device to 20.10%(PMo₁₁V),20.42%(PMo₁₀V₂)and 20.90%(PMo₉V₃).