Research On Improvement Of Photoelectric Properties Of PSCs By Polyoxometalate-regulated Election Transport Layer

As the new star in the field of photovoltaics,perovskite solar cells（PSCs）have become a research hotspot due to their low cost and high efficiency.In perovskite solar cells,the electron transport layer functions to transport photogenerated electrons,so the performance of the electron transport layer will seriously affect the photoelectric conversion efficiency of the battery.The amorphous WO_x electron transport layer is prepared under low temperature conditions.Compared with the current high-efficiency PSCs,the device preparation cycle is shortened,and the preparation cost is saved,but the formed electron transport layer film has many defects and poor conductivity.The conventional TiO₂ electron transport layer has poor conductivity and catalytically decomposes the light absorbing layer.The disadvantages of the above described electron transport layers limit further improvements in battery performance.Heteropolyacids have the advantages of matched energy levels,good electrical conductivity,and suitable molecular size.In this paper,heteropoly acid is used to modify and replace the electron transport layer materials in PSCs to make up for the shortcomings of the above electron transport layer materials,thereby improving the photovoltaic performance of PSCs.The PSCs of the composite PW₁₂-WO_x electron transport layer were constructed by heteropoly acid H₃[PW₁₂O₄₀]·nH₂O(abbreviated as PW₁₂)and amorphous WO_x,which shortened the device preparation cycle,reduced the preparation cost,and improved the photoelectric conversion efficiency of the battery from 12.51%.To 14.38%,the efficiency increased by 14.9%.Two kinds of batteries were tested for fluorescence emission（PL）,electrochemical impedance spectroscopy（EIS）,open circuit voltage decay curve test（OCVD）,and monochromatic photo-electrical conversion efficiency（IPCE）,which were found from the internal charge transfer mechanism of the battery.After the modification,the electron transport layer improves the transmission efficiency of photogenerated electrons,and the composite behavior of electrons and holes in the battery decreases.Through the analysis of the surface morphology of the electron transport layer and the perovskite film,it was found that the defects of the electron transport layer film were significantly reduced after modification,and the crystal structure of the perovskite layer was better.The heteropoly acid Na₁₀[Co₂Bi₂W₂₀O₇₀]completely replaced the traditional TiO₂mesoporous layer material,which solved the decomposition of TiO₂ on the perovskite layer under ultraviolet light irradiation,and improved the photoelectric conversion efficiency of the battery from 14.21%to 15.79%,which improved 11.11.%.The open-circuit voltage decay test（OCVD）,electrochemical impedance spectroscopy（EIS）,and monochromatic photo-electrical conversion efficiency（IPCE）tests were performed on the two batteries.The electron transport layer was absorbed by the internal charge transfer mechanism.The photogenerated electrons generated by the layer have higher transmission efficiency,and the composite behavior of photogenerated electrons and holes inside the light absorbing layer is suppressed.The morphology of mesoporous layer and perovskite layer was analyzed,and the perovskite film of heteropolyacid Na₁₀[Co₂Bi₂W₂₀O₇₀]was better in quality and the grain size of perovskite was larger.Through the stability analysis of the two batteries,it was found that the heteropoly acid Na₁₀[Co₂Bi₂W₂₀O₇₀]showed better stability for the mesoporous battery.