Design, Synthesis And Characterization Of Novel D-A Conjugated Polymers For Organic Solar Cell

It is clear that the current energy regimen,which relies on nonrenewable and polluting energy sources,has unsustainable consequences for societal,economical,geopolitical,and environmental issues.The only fully renewable source that has the capability to meet the world's large and growing energy demand is solar energy.Thin film polymer solar cells(PSCs)hold promise for fabricating lightweight and flexible devices via the low-cost and high-throughput roll-to-roll production process.Extensive research efforts around the world have been devoted to constructing and synthesizing the struture of the material and improving the performance of PSCs in rescent years.Upon on this,Design and Synthesis of appropriately low band gap polyer based on D-A conjugated polyer is the main task in this article and then we characterise the physical,optical and photovaltic properties intending to abtain active layers with high performance applying on PSCsChapte 2: Three new donor-acceptor(D-A)type of conjugated polymers,with 1,1-diheptyl-3,4-diphenyl-2,5-bis(4,7-dithienyl-2,1,3-benzothiadiazole)-silole as acceptor unit,were synthesized through palladium-catalyzed Stille polymerization.The resulting polymers exhibit a broad absorption spectrum(from 350 to 850 nm)and excellent thermal stability with decomposition temperature up to 400°C.The HOMO energy levels of polymers are lower than-5.1 e V,and the LUMO energy levels of them are higher than-3.7 e V,so the three polymers are promising donor materials for polymer solar cells(PSCs).Bulk-heterojunction(BHJ)PSCs based on an inverted device configuration of ITO/PFN/PDTBDT-HSTBT:PC61BM/Mo O3/Ag showed good photovoltaic performance with power conversion efficiency of 3.24%,which is the best reported among PSCs fabricated from 2,3,4,5-tetraarylsilole-based polymersChapter 3:Through the latest progress,we incorporate the sulfer atom based on alkythio-substituted BDT unit.We use two different side chain to modify DPP and ID based units and then successfully synthesied four D-A conjugated polymer named P1,P2,P3,P4.The change from different amount of carbon atoms in the side chain caused similar optical and physical properties,but exhibit a extremely diffrence in photovaltic performances.The DPP based conjugated polymer exhibits low band gap about 1.3 e V and ID based conjugated polymer have a HOMO level at about-.54 e V which is the proper HOMO in idealized Polymers.Thephotovoltaic properties of these polymers were investigated using the device configuration of ITO/PFN/PDTBDT-HSTBT:PC61BM /Mo O3/Ag.The highest achievable PCE for P1,P3 is 3.86% and 3.63% respectively.Chapter 4:We continue untilize the two different alkythio-substituted BDT units incorating the sulfer atom as the donor units and naphtho[1,2-c:5,6-c]bis[1,2,5]-thiad iazole(NT)derivative as the acceptor unit,two low band gap D-A conjugated copolymers by still cross-coupling polymerization have been designed and synthesized for polymer solar cells,which named PBDT-TS1-DTNT and PBDT-TS2-DTNT.NT contains two fused 1,2,5-thiadiazole rings that can lower the band gap,enhance the interchain packing,and improve the charge mobility of the resulting polymer.PBDT-TS2-DTNT show a high power conversion over 5%.