Research On The Synthesis Of Anion-doped Fullerene Derivatives And Interface Regulation On Perovskite Solar Cells

The development of efficient and stable perovskite solar cells（PSCs）technology is contributed to achieve carbon peaking and carbon neutrality goals proposed by the state and relieve the energy problems facing mankind.The power conversion efficiencies（PCEs）of PSCs have dramatically improved from 3.8%to a certified value of 25.5%,reaching a level that can compete with commercial silicon solar cells.However,the commercial application of perovskite solar cells still needs to further improve their efficiency and stability.The interface properties of perovskite solar cells are important factors affecting device efficiency and long-term stability.The well-matched energy level,excellent carrier separation efficiency,low density of defect states,and good ability to resist water erosion of interlayer interface help to improve the power conversion efficiency and stability of the devices.In view of this key problem,this paper proposes the design and synthesis of new anion-doped fullerene derivatives as interface modification material to regulate interface properties,so as to adjust band distribution,reduce defect density,depress non-radiative recombination center,promote charge extraction and separation,and improve device power conversion efficiency and stability.For this purpose,we have mainly carried out the following three parts of the work:In order to regulate the perovskite interface properties,four anion-doped fullerene derivatives are designed and synthesized in a concise and efficient method.The optimal synthesis process conditions were studied experimentally,and their structure was confirmed by various modern testing means.After that,we have successfully applied them as interface modification materials for perovskite in inverted plane structured solar cells.The device power conversion efficiency with those fullerene derivatives as interface modification materials for perovskite was increased from 14.96%to a maximum of 17.63%,and the device is able to maintain 85%of the initial efficiency after storage for 500 h at ambient environment.The corresponding mechanism research results show that these anion-doped fullerene derivatives possess higher conductivity and electron mobility than conventional fullerene derivatives and can promote charge transfer between perovskite and the electron transport layer.At the same time,the unique quaternary ammonium salt groups in these fullerene derivatives make them have excellent defect passivation ability,which can significantly reduce the density of defects at the perovskite surface and crystal boundary and depress the carrier non-radiation recombination,thus improving the efficiency and stability of the devices.To improve the properties of electron transport materials and regulate the properties of perovskite interface,perylene diimide（PDI）and two fullerenes are skillfully incorporated to obtain a novel anion-doped fullerene dimmers derivative C₆₀-PDI-I as an electron transport material for perovskite solar cells to replace the traditional fullerene-based electron transport material（PCBM）.C₆₀-PDI-I used as an electron transport material for perovskite solar cells could improve the power conversion efficiency from 15.60%to 18.92%and the devices,stability also been improved obviously.After that,we investigating the interaction mechanism between C₆₀-PDI-I and perovskite by space charge limited current method and X-ray photoelectron spectroscopy etc,the results show that the presence of anion-doping properties significantly increases the conductivity and electron mobility of C₆₀-PDI-I,and the application of C₆₀-PDI-I as electron transport materials could boost the charge extraction and transport.In addition,the unique quaternary ammonium salt groups and abundant N and O atom in the C₆₀-PDI-I play a good role for defects passivation at the perovskite surface and crystal boundary.Under the combination of the above effect,the power conversion efficiency and stability of the device have been greatly improved.The unmatched energy levels between the metal electrodes and electron transport material cause a large energy level barrier between the adjacent interface.In order to regulate the interface properties between metal electrode and electron transport material,we have designed and synthesized a novel anion-doped fullerene-based ionene polymer(C₆₀-MPE-ionene),and applied it as cathode modification materials for perovskite solar cells.This fullerene ionene polymer possess a high electron mobility that not available by conventional ionene polymer.More important,this compound has good conductivity due to the presence of anionic doping properties.The application of C₆₀-MPE-ionene as an interlayer between the electron transport layer and metal electrode can reduce the work function of the Ag electrode from 4.58 e V to3.96 e V,decrease the energy barrier between adjacent layers,and boost charge transfer.The C₆₀-MPE-ionene modified device efficiency was improved from 15.60%to 19.28%,with no significant hysteresis effect.Moreover,C₆₀-MPE-ionene-modified cells exhibited enhanced environment stability compared with pristine cells due to the hydrophobicity of C₆₀-MPE-ionene and satisfactory film coverage that inhibit the decomposition of MAPbI₃ film.