Synthesis Of Hole-Transporting Materials For Indenone-Spirofluorene-Aniline-Type Perovskite Solar Cells

The discovery,development and application of perovskite solar cells are inseparable from hole-transporting materials.Among them,Organic small-molecule hole transporting materials are the most widely used and have attracted widespread attention in recent years.The discovery of new high-performance hole transporting materials requires three steps: design and synthesis of new molecules,analysis of basic photoelectric properties and further optimization to improve their properties.However,the reports of hole transporting materials have mainly focused on the core materials with 9,9'-spirobi [fluorene](SBF),spiro [fluorene-9,9'-xanthene](SFX).The types of materials are limited.At the same time,the challenge of synthesis restrict their further applications.Therefore,the search for new hole transporting materials is the biggest problem facing this field.In view of this situation,in this paper,9,9'-spirobifluorene is selected as the structural unit.After the indenone group is introduced into the skeleton structure,the ?-conjugated system can be extended to effectively adjust the intramolecular electronic structure and improve the frontal orbital energy level.Then,three-dimensional structure molecules SFD-TPA,SFD-OMe TPA,SFD-TAD and SFD-OMe TAD based on indenone-spirofluorene as the core and diphenylamine or triphenylamine as the branch were designed and synthesized.In the preparation process of the target molecules,a total of 9 steps including acylation,ring closure,reduction,bromination,oxidation,Suzuki-Miyaura coupling reaction and Buchwald Hartwig coupling reaction are involved.All products were characterized and confirmed by nuclear magnetic resonance hydrogen spectroscopy,carbon spectroscopy,high-resolution mass spectrometry and infrared spectroscopy.Subsequently,this paper combined with ultraviolet-visible absorption spectroscopy,cyclic voltammetry and density functional theory calculations to study the photophysical properties,electrochemical properties and front-line orbital energy levels of the target products.The results show that both SFD-TPA and SFD-OMe TPA show good optical and electrochemical stability,and the target products SFD-OMe TPA with triphenylamine methoxy as a branch exhibit slightly deeper highest occupied molecular orbital energy levels than the compounds SFD-TPA with triphenylamine as a branch.The front-line orbital energy levels of the four compounds are comparable to the energy levels of the commonly used hole transporting material spiro-OMe TAD.They can all be well matched with the perovskite layer and metal counter electrode and suitable for use as hole transporting materials.The research in this paper provides a new idea for designing new hole transporting materials,enriches the types of organic molecules and plays an important role in the field of perovskite solar cells.