| The new thin-film perovskite solar cell has become the most promising solar cell technology in the photovoltaic field due to its advantages such as high efficiency and low cost and simple preparation process.At present,the certification efficiency of its laboratory devices has reached 25.2%,equivalent to that of commercial silicon solar cells.However,the instability of perovskite films and devices under external conditions such as water,oxygen,heat and light greatly limits their commercial application.The replacement of traditional lead-based perovskites with tin-based perovskites can effectively reduce the environmental pollution caused by the biological toxicity of lead,but the development of tin-based perovskite solar cells is still far from that of lead-based perovskite solar cells due to the difficult film morphology and oxidation instability.The research in this paper focuses on improving the efficiency and stability of perovskite solar cells,aiming to achieve the coordination of perovskite internal carrier transport regulation and grain boundary(GB)hydrophobic through additive engineering,so as to solve the stability problems faced by perovskite solar cells.Organic-inorganic hybrid perovskite solar cells are prone to performance degradation under the external water and oxygen environment and high temperature conditions.The infiltration of water and oxygen in GB of perovskite and the spontaneous migration of internal ions are the two main factors restricting its long-term efficient and stable operation.The semiconductive molecule N,N'-bis-(1,1,1,2,2,3,3,4,4-nonafluorododecan-6-yl)-perylenediimide(F-PDI)was first introduced into the GBs of the perovskite film,and it was found that the device's photovoltaic performance,as well as thermal and moisture stability is enhanced simultaneously.The conductive F-PDI molecules filling at GBs and surface of perovskite film can passivate internal defects,and its large rigid ?-conjugated plane is conducive to the transfer of charge at the GBs.In addition,the hydrophobicity of fluorine protects the perovskite film from moisture,and the strong hydrogen bonding between F-PDI and perovskite can immobiliz methylamine ions to inhibit their internal migration.As a result,the optimized device achieved the highest efficiency of 19.26%and was able to maintain 80%of its initial value after 30 days of aging in air with relative humidity(RH)of about 50%or high temperature heat treatment(85?)for 24 hours,presenting excellent humidity stability and thermal stability.We demonstrate that the morphology,crystal orientation,and environmental stability of the formamidinium tin triiodide(FASnI3)film were regulated by the conductive hydrophobic molecule F-PDI.Studies have shown that the introduction of F-PDI during the growth of perovskite films increases the perovskite grain size and promotes the crystal growth in the vertical direction.In addition,the carbonyl group in F-PDI can provide lone pair electrons and chelate with uncoordinated tin atoms in perovskite to passivate the defect state and improve the film quality.At the same time,F-PDI exists in the GBs of FASnI3 film can serving as a medium for charge transport,which promotes the effective transport of carriers at the GBs and interfaces,and effectively improves the photoelectric performance of the device.These favorable factors have made the photoelectric performance of FASnI3-based devices significantly improved,and achieved an energy conversion efficiency of 7.36%.In addition,the distribution of hydrophobic F-PDI at the GBs and interface of perovskite greatly enhances the intrinsic hydrophobicity of the perovskite film and blocks the penetration of oxygen,so that the unencapsulated F-PDI modified device was able to maintain about 70%of its original efficiency even after being exposed to air with a 50%RH for 10 hours. |
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