Synthesis Of Small Organic Molecule Hole-transporting Materials And The Application In All-inorganic Perovskite Solar Cells

Hole transport materials(HTMs)play important roles in transporting holes,inhibiting carrier recombination,promoting perovskite crystallization,and protecting perovskite layers in perovskite solar cells(PSCs)and PSCs photovoltaic performance is greatly affected by its performance.This paper aims to explore the effect of small-molecule hole transport materials on the photoelectric properties of all-inorganic PSCs and provide guidance for the synthesis of new and efficient stable HTMs.we synthesized nine organic small molecule HTMs to explore the effects of fluorine,chlorine atoms,molecular spatial structure on the photoelectric properties,electrochemical properties of the materials and apply them to all-inorganic CsPbBr₃perovskite solar cells.The detailed results were briefly described as below:1)Using benzodithiophene(BDT)as the core unit,we have synthesized three two-dimensional planar small molecule hole transport materials BDT-H?BDT-F and BDT-Cl.The BDT-F and BDT-Cl are modified by fluorine and chlorine atoms.Compared with the BDT-H,the fluorine and chlorine atoms will cause a small red shift of UV absorption peak,which will deepen the HOMO energy level and decrease the LUMO energy level of the molecule The photoelectric conversion efficiency(PC E)of 7.49%,8.09%and 8.14%was obtained by applying BDT-H?BDT-F and BDT-Cl to all-inorganic CsPbBr₃ perovskite solar cells,respectively,indicating that BDT series of organic small molecule hole transport materials are beneficial to improve the performance of the device2)Using 2,2'-Bithiophene as the core unit,we have synthesized three three quasi-three-dimensional oligothiophene small molecule hole transport materials BT-BTE?BT-OCT and BT-IOCT.BT-IOCT,due to its oblique cross-type molecular space structure and the introduction of soluble isooctane chains,showed a colloidal state at room temperature.Compared with the classical hole-transporting material Spiro-OMe TAD,BT-OCT obtained 8.63%PCE,by virtue of good solubility and film-forming property,indicating that the quasi-three-dimensional spatial structure can improve the film-forming property of the material,which is beneficial to the improved photoelectric conversion performance of the device.3)Using 4-Bromo-spiro[9H-fluorene-9,9'-[9H]xanthene]as the core unit,we have synthesized three three three-dimensional structures small molecule hole transport materials SFX-THIO1?SFX-THIO2 and SFX-THIO3.Different amounts of thiophene as four arms increase the three-dimensional structure of molecular space,reduce the interaction between molecules,prevent the close accumulation of molecules,and ensure their solubility With the increase of thiophene number,the UV absorption peak is red-shifted,and the HOMO and LUMO energy level of the material are increased,which also laid the foundation for obtaining the suitable energy level of the material by adjusting the amount of thiophene.The higher lumo energy level can effectively block the transfer of electrons from the perovskite layer to the carbon electrode,and ensure the effective injection of electrons into the electron transport layer.The PCE of6.65%,7.05%and 7.62%is obtained by applying SFX-THIO1?SFX-THIO2 and SFX-THIO3 to all inorganic CsPbBr₃PSCs,respectively.