Synthesis And Properties Research Of D-A Polymer Donor Materials Based On 3-fluorothiophene

Organic solar cells(OSCs)have significant development and application prospects due to the superiorities such as light weight,easy processing and flexibility.Nowadays,18%energy conversion efficiency has been achieved in non-fullerene OSCs.The rapid development of OSCs in recent years is mainly due to the development of highly efficient active layer materials.As an important part of OSCs,donor and acceptor materials determine the performance of photovoltaic devices to a large extent.Therefore,the design of new and efficient active layer materials is of great significance for the early commercialization of OSCs.This paper briefly introduces the development history of OSCs and the key donor and acceptor materials.At the same time,it proposes a simple and efficient synthesis method for introducing3-fluorothiophene into the main chain.On this basis,two types of benzodithiophene(BDT)-based polymer donor materials were designed,and the effects of the introduction of halogen heteroatom on the surface morphology,thermal stability,UV-visible absorption,energy band gap and photovoltaic performance was systematically investigated.The main research content is as follows:1)Three D-?-A polymer donor materials(J52FH,J52FCl and J52FF)were designed and synthesized using BDT as electron donor unit,3-fluorothiophene as?bridge and BTz as acceptor unit.The results show that three polymers have similar spectral absorption range of 300-650 nm,and there are effective exciton disintegration and charge transfer between the polymers and the acceptor materials.Electrochemical studies have shown that the HOMO energy level of the material can be greatly lowered by implementing fluorination strategy on the?bridge of the main chain.The PCE of the reverse photovoltaic device based on J52FF reaches 13.93%,which is the highest level that can be obtained based on BDT-?-BDZ polymer donor and higher than 9.96%and 10.52%of J52FH and J52FCl.Its V_oc,J_scand FF are 0.89 V,22.27m A cm^-2and 70.3%,respectively.The results indicate that fluorination on the main chain is an effective strategy to obtain high performance reactive layer materials.2)Based on the important intermediate of 3-fluorothiophene,three D-?-A polymer donor materials(PBDB-TFH?PBDB-TFCl and PBDB-TFF)were designed and synthesized using BDT as electron donor unit,3-fluorothiophene as?bridge and BDD as the acceptor unit.The results show that three polymers exhibit similar absorption peaks in the absorption range of 300-700 nm,and at the same time exhibit lower HOMO levels.The reverse photovoltaic device based on PBDB-TFF:IT-4F reached the PCE of 12.05%,and the corresponding V_oc,J_scand FF are 0.92 V,20.06m A cm^-2and 65.30%,respectively.It can be seen that fluorination in the main chain is beneficial to reduce the HOMO level of the material,and the steric hindrance and electronegativity of the heteroatom introduced in the side chain will also affect the performance of the photovoltaic device.