Hole Transport Material Based On Asymmetric Fluorene-dithiophene Core Structure

Energy crisis and world environmental pollutions have made it particularly important to find and develop new clean energy sources,and the research on renewable energy has brought breakthroughs in solving this problem.As the richest and cleanest energy source,solar energy is the most promising among the currently known renewable energy sources.Solar cells can convert light energy into electrical energy.Among them,perovskite solar cells have been a hot research topic in recent years.Perovskite solar cells(PSC),which were first reported in 2009,have so far achieved a huge increase in photovoltaic efficiency from 3.8% to 25.2%.Hole transport materials play an important role in perovskite solar cells and have an important impact on the photoelectric conversion efficiency and stability of the cell.In perovskite solar cells,the most widely used organic hole transport material is Spiro-OMe TAD,which is expensive and has poor thermal stability.This thesis took fluorene-dithiophene as the core structure,and finally synthesized five organic hole transport materials by introducing different numbers and positions of phenylenediarylamine groups and benzenetriarylamine groups.The starting material of the target compound was bithiophene.The experiment was conducted through a seven-step reaction including Ullmann reaction,Suzuki coupling reaction,Buchwald-Hartwig reaction and other reactions.The target product was synthesized,and then purified,and performed by methods such as hydrogen NMR,carbon NMR,and mass spectrometry.Structure confirmation and characterization finally proved that the synthesized target molecules were all designed molecules.The optical and electrochemica properties test of the five synthetic hole transport materials mainly included the determination of ultraviolet-visible absorption spectroscopy and redox potential.The introduction of benzenetriarylamine group on the thiophene group would cause the red shift of the ultraviolet absorption spectrum,the absorption intensity would become larger,the range would become wider,and the energy required for electronic transition would reduce.These changes are conducive to the freeing of electrons and holes.According to the redox potential of the target compound,it was calculated that the HOMO energy level of the five hole transport materials was higher than the HOMO energy level of Spiro-OMe TAD,and the HOMO value was greater than the valence band energy level of the perovskite material,these results showed the great potential of the designed molecules as hole transport materials in perovskite solar cells.