Design And Synthesis Of Heteroatom-Containing (Oxygen,Sulfur) Organic Small Molecule Hole Transport Materials And Their Application In Perovskite Solar Cells

Perovskite solar cells(PSCs)have become a research hotspot in the field of solar cells due to their excellent photoelectric properties.Hole transport materials(HTM)has important significance in the extraction and transport of holes in high-performance PSCs structures.The development of new and efficient HTM is of great significance for achieving high-performance and low-cost PSCs.Researchers often optimize the characteristics of molecules by adjusting the molecular structure and introducing special functional groups.Oxygen-containing or sulfur-containing functional groups are widely used in HTM structural units due to their good interaction with perovskite materials,promoting film formation and regulating energy levels.In this paper,oxygen-containing(furan,methoxy)or sulfur-containing(thiophene,methylthio)functional groups are introduced into the new small molecule HTM as conjugated bridges or terminal groups,and the effects of heteroatom changes on the light absorption,energy level,hole mobility and molecular configuration of the materials are further compared and explored.Finally,it is applied to mesoporous n-i-p PSCs to obtain more efficient device performance.The main research contents and outcome are as below:(1)Based on the thiophene bridge molecule(FT-OMeTPA),a molecule with furan as a conjugated bridge(FF-OMeTPA)was designed and synthesized.FF-OMeTPA shows a better planar configuration than FT-OMeTPA,which also makes the FF-OMeTPA molecules more compact during stacking and the formed film more flatter.In addition,the furan bridge molecule FF-OMeTPA itself has higher electrical conductivity and hole mobility,and the flat film morphology makes the combination between the FF-OMeTPA film and the perovskite layer closer,which further promotes the transport of holes at the interface.When applied to PSCs,the photoelectric conversion efficiency(PCE)of FFOMeTPA devices is 21.82%,which was much higher than the PCE of 18.01%of FTOMeTPA device and exceeded the PCE of 21.02%of spiro-OMeTAD reference device.(2)Based on the molecule H-alk composed of butyl carbazole and methoxytriphenylamine,the molecules H-oxy and H-sulf were designed and synthesized by introducing methoxy and methylthio groups at the butyl end,respectively.The oxygen and sulfur terminal of the new material show electronegativity,which can passivate the defects.In addition,compared with H-alk,the new molecules H-oxy and H-sulf showed higher conductivity and hole mobility.Compared with H-sulf,the oxygen-containing material H-oxy has stronger hole extraction and transport capacity.For another thing,it is due to the high hole mobility of H-oxy material itself.On the other hand,due to the poor tol erance of H-sulf to additives,the contact with perovskite layer and the transport of holes are affected.When the three materials were applied to PSCs,the device based on H-oxy obtained 17.78%PCE and H-sulf obtained 16.25%PCE,which exceeded the 15.00%PCE based on H-alk.