Synthesis And Research Of Small Molecule Acceptor Materials For Non-fullerene Organic Solar Cells

Solar energy is a renewable green energy,an organic solar cell(OSC)is a device that can convert solar energy into electric energy.Because of its flexibility,ease of large-area print,light weight,simple prcessing,low cost,and other advantages,OSC has received widespread attention.At present,the highest photoelectric conversion efficiency of OSC based on the Fused-ring receptor Y6 series has reached 17%,but there are still few high-efficiency OSC materials,so it is very important to develop new materials.The donor and acceptor materials in the active layer of OSC are key factors that affect the photoelectric conversion efficiency of the device.In this thesis,asymmetric molecules and simple and completely non-fused ring acceptors are designed and synthesized,and the effects of conjugate length and flexible side chains on organic solar cells are studied.The results are as follows:1.Three small molecule acceptor materials,ZLT-EH-4F,ZLTT-EH-4F and ZLTT-BO-4F,were designed and synthesized by constructing an asymmetric system.ZLTT-EH-4F and ZLTT-BO-4F with longer conjugated units of the three small molecules have a wider absorption range(450-760 nm),while ZLT-EH-4F has a narrower absorption range(500-700 nm).Among them,ZLTT-BO-4F has better solubility and more suitable crystallinity due to its longer flexible side chain.The photoelectric conversion efficiency of the device prepared by blending it with the polymer donor material PBDB-T is as high as 9.53%.The photoelectric conversion efficiencies of the devices prepared by blending ZLT-EH-4F with short conjugation length and ZLTT-EH-4F with poor solubility and the same donor are only 2.83% and4.49%,respectively.The results show that the appropriate conjugation length and solubility have a significant impact on the photoelectric conversion efficiency of organic solar cells.2.Two completely non-fused ring small molecule acceptors,4T-out-4F and4T-in-4F,were designed and synthesized.They are isomers but exhibit different photoelectrochemical properties.After same annealing treatment for the two material films,the former has a strong absorption in the range of 530-820 nm,and the latter in the range of 610-1050 nm.Analysis shows that this is due to the fact that 4T-in-4F molecules easily form J-aggregation in the solid state.This aggregation is similar to other types of intermolecular interactions(hydrogen bonds,S···O,etc.)and helps to build the 3D interconnection "network",facilitating multi-dimensional charge transport.The photoelectric conversion efficiency of OSC using PBDB-T as donor,4T-in-4F and 4T-out-4F as acceptors,were 5.69% and 3.23%,respectively.