Design And Synthesis Of Benzodithiophene Based Double-cable Polymer And Its Application In Single-component Organic Solar Cells

Solar energy,as a universally available clean energy,has attracted countless attention.Compared with traditional inorganic silicon batteries,organic solar cells have the advantages of low cost,low pollution,and flexible fabrication of devices,which has become a hot spot in the field of photovoltaic research in recent years.Compared with bulk heterojunction organic solar cells,the efficiency of single component organic solar cells（SCOSCs）is obviously lagging behind,but because the active layer has only one component which is easier to realize highly stable devices,and it has also been widely studied.This thesis focuses on the design,synthesis,and morphology of materials of active layer for single-component organic solar cells.We have designed and synthesized a donor polymer which is composed of benzodithiophene（BDT）and benzodithiophene dione（BDD）as the conjugated backbone connected by dialkyl with perylene imide（PBI）as the acceptor side chain unit,and we called it the double-cable conjugated polymer.Then we have characterized its thermal,optical and electrochemical properties,and successfully applied to single-component organic solar cells.The main contents are as follows:1.Summarized the active layer materials of a variety of single-component polymer solar cells,compared several widely studied materials that have been widely reported,and understood the characteristics of active layer materials,device fabrication processes,material characterization techniques,etc.According to the previous research results of our research group,the current highest performance device of PBDBPBI-S was modified,based on the design of the donor-acceptor double-cable conjugated polymer Strategy,we have designed and synthesized a new D-A double-cable conjugated polymer based on benzodithiophene.First,a donor material based on BDT is synthesized,and then the acceptor side chain PBI is connected to the donor through a flexible alkyl chain.After replacing the aromatic bridging group thiophene of monomer BDD with selenophene,we copolymerized BDD with BDT and the polymer PBDBPBI-Se was obtained.The test found that the number average molecular weight M_nof the polymer was 47.1 kg mol^-1,the weight average molecular weight M_wwas 82.4 kg mol^-1,and the dispersibility index PDI was 1.75.The absorption spectrum shows that PBDBPBI-Se has a wider absorption spectrum,so it is expected to obtain higher energy conversion efficiency when applied to single-component organic solar cells.2.Using PBDBPBI-Se as a single-component active layer material to prepare organic solar cells devices,we found that as the annealing temperature increases,the hole and electron mobility are further improved.After comparing several different annealing temperatures,the best result was obtained when it was annealed at 230°C.J_scwas enhanced to 12.68 m A cm^-2,V_ocwas 0.84 V,FF was 0.58,and energy conversion efficiency was 6.25%.The enhanced J_scis due to the wider absorption spectrum of the PBDBPBI-Se based device,while the low V_ocis due to the lower HOMO energy level of the PDBBPBI-Se.Then tested the AFM morphology of the device,GIWAXS MAXS crystallographic characteristics,etc.The results show that after thermal annealing,the crystallinity of the film is enhanced,the crystal structure is more ordered.