Design,Synthesis And Properties Of Organic Small Molecule Hole Transport Materials Based On Polysulfide System

The excellent performance of perovskite solar cells(PSCs)has made it popular in various fields.It has been widely used because of its excellent photoelectric conversion efficiency and the advantages of simple processing and lower price.According to research,its power conversion efficiency(PCE)has reached 25.7%,and the efficiency of this achievement has basically met the requirements of commercialization.Hole transport material(HTM)plays a key role in this kind of energy cell and has been widely studied,but there are still some issues to be further investigated for the design and development of materials with high energy level matching,solution processability,and balance between film formation and crystallinity.The research work in this thesis aims to synthesize organic small molecule hole transport layer materials based on polysulfide system and to investigate their properties by modulating the structure of small molecules,thus it is important for us to effectively use molecular design strategies to obtain new HTM molecules.The following three main aspects were studied:1.HY-1,an asymmetric molecule based on tetrathiafulvalene(TTF)derivatives with iodinated phenyl and pyridine groups directly linked to the TTF core,was designed and synthesized.The self-assembly properties of the molecule in different solvents(heptanoic acid and 1-phenyloctane)at the highly oriented pyrolytic graphite(HOPG)interface were investigated,and the main weak interactions of the two-dimensional nanostructure of the HY-1 molecule in different solvents were elucidated by scanning tunneling microscopy(STM)method.The helical structure of triphenylamine can regulate the film-forming property,and the molecule HY-2 with triphenylamine branching was designed.The synthesis steps were simple,and the structural characterization of the molecules determined that the synthesis was correct,and the thermal stability analysis of the two molecules showed that the materials have good thermal stability,and the tests of electrochemical properties and energy level calculations concluded that the energy levels of the two materials can match well with the valence bands of PSCs and inject holes effectively.2.HY-3 and HY-4 molecules containing asymmetric structures of isophthalic acid groups were designed and synthesized.There is an anchoring effect between the carboxylic acid group of isophthalic acid and ITO(Indium Tin Oxide)glass,and the ITO glass can be anchored by the single atomic level dispersion of surface carboxylic acid roots to form self-assembled monomolecular films,but their solubility is poor and the efficiency of the prepared devices is low.Further synthesized HY-5 molecule with TTF derivative as the central group asymmetry,which can effectively prevent water penetration into the chalcogenide layer by introducing alkyl chain modified end groups,making the molecule hydrophobic,regulating film formation and solution processable,while the solubility is greatly enhanced.And the single crystal structure of HY-5 molecule was obtained,and the photocurrent test observed that the molecule has a uniform photocurrent.3.By introducing amine functional passivation groups,the passivation effects of three symmetric structured aniline molecules HY-6,HY-7 and HY-8 with TTF group as the central group and aniline,benzylamine and benzamidine groups as the end groups were investigated and synthesized.The results show that the amine group can be anchored to the Pb-I backbone of chalcogenide through hydrogen bonding,forming a hydrophobic passivation layer that can prevent water molecules from penetrating into the PSCs,thus improving the stability of the devices.Good performance was achieved by using HY-6 and HY-7 as HTM to prepare transPSCs devices,and the best efficiencies of 12.5%and 16.1%were obtained,respectively.The symmetrically structured TTA molecules were used as HTM to prepare the forward PSCs devices with the highest efficiency of 18.9%at a concentration of 0.01 mg/mL.Using the solvent effect,the green solvent THF was used instead of chlorobenzene solvent to enhance the device efficiency by upgrading the morphology and particle size of the amidine PSCs active layer.