Synthesis And Properties Of Acceptor Materials For High-efficiency Organic Solar Cell

Owing to the advantages such as low cost,light weight and can be fabricated by solution,the organic solar cells(OSCs)have attracted wide attention in the academic world and the industrial world.However,the low power conversion efficiency of OSCs is the main factor that restricts the application of OSCs.Therefore,new OSCs materials are currently one of the key research areas in materials science.In this thesis,we designed and synthesized a series of small molecule and polymer acceptor materials and applied them to organic solar cells to explore the relationship between the structure of acceptor materials and the performance of organic solar cells.The work of this thesis is summarized as follows:In chapter 1,the background knowledge of organic solar cell principle,structure,performance parameters,materials and research methods were introduced.In chapter 2,We designed and synthesized a novel electron withdrawing unit CPTCN,and then we designed and synthesized a novel small molecule acceptor material ITCPTC using CPTCN as a capping material.OSCs based on the electron donor materials PBT1-EH and ITCPTC show a large open circuit voltage(0.95 V),a large short circuit current(16.5 mA cm-2)and a very high fill factor(75.1%)The power conversion efficiency reached 11.8%.We found that changes in the capping unit not only change the electronic structure of the molecule itself,but also affect the interactions between the materials and the crystallization process.In chapter 3,the donor core is replaced with a smaller IDT unit,a new type of small molecule receptor material IDTCN is designed and synthesized.OSCs based on the electron donor materials PBTl-EH and ITCPTC show a large open circuit voltage(0.93 V),a large short circuit current(13.31 mA cm-2)and a very high fill factor(70.2%)The power conversion efficiency reached 8.69%.Smaller donor unit are not conducive to expanding the absorption spectrum of small molecule materials,and therefore performance is reduced.At the same time,the molecular stacking of IDTCN is also very different from that of ITCPTC.This shows that the choice of donor core is very important for designing small-molecule receptor materials.In chapter 4,ITIC,a common small molecule acceptor material,was used as the polymer structural unit.Two polymer acceptor materials PVITIC and PIT-IC were designed and synthesized.PBDB-T was used as electron donating material.OSCs based on PVITIC shows an open circuit voltage of 0.78V,a short circuit current of 2.07 mA cm-2,a fill factor of 39.3%and a power conversion efficiency reached 0.63%.OSCs based on PIT-ITIC show an open circuit voltage of 0.913 V,a short circuit current of 4.46 mA cm-2,a fill factor of 35.0%and a power conversion efficiency reached 1.42%.The experimental results show that the large bridging units with dissolved alkyl chains can give better solubility and therefore can form better morphologies,resulting in higher efficiency.