Synthesis Of Novel DA Organic Conjugated Polymer Donor Materials And Solar Cell Performance Studies

The issues such as energy crisis and environment pollution are becoming more and more serious with the development of the society,it is highly desirable to develop clean and renewable energy systems.Solar cells have attracted great attention because solar energy is green,clean and renewable energy on the earth.In the past decades,organic solar cells(OSCs)have attracted broad interest because of their light weight,low-cost,flexible,and easy fabrication,and great progress has been made,particully in the conversion efficiency of single section solar cells(12%).However,there are many problems need to be solved before any commercial application of organic solar cells.The most important one is the design and synthesis of novel high-performance polymer materials,apart from the stability and optimization of the device.In the thesis,we mainly focused on the design and synthesis of donor and acceptor polymer materials for the heterojunction(BHJ)organic solar cells.We designed and synthesized three series of D-A conjugated polymers,and investigated their thermostability,optical and electrochemical properties,and photovoltaic performance.The major contents and results are summarized as follows:1.We designed and synthesized a new donor-acceptor(D-A)copolymer of POPHF2T with wide optical bandgap based on alkoxy-phenylene as the donor and di-fluoride bithiophene as the acceptor.Compared with P3HT,POPHF2T exhibited wider bandgap of 2.10 eV,demonstrating that POPHF2T is a potential polymer material for tandem solar cells and multiple batteries.It was found that POPHF2T possessed high LUMO energy level so that we need to find an acceptor with the matched LUMO energy level.The device based on POPHF2T:PC71BM gave a power conversion efficiency of 4.47%.2.We designed and synthesized two D-A copolymers PSTTF2T and POTTF2T with moderate bandgaps,and investigated the influence of alkylthio(-SR)and alkoxy(-OR)chains on the photovoltaic performance.Compared with the alkoxy-substituted analogue,PSTTF2T poseesses a deeper HOMO level and a higher hole mobility because of the intermolecular S-S interaction facilitating ?-? stacking.PSTTF2T:PC7iBM and PSTTF2T:ITIC solar cells gave PCE of 4.73%and 5.22%,respectively.POTTF2T:PC7iBM and POTTF2T:ITIC solar cells gave PCE of 1.93%and 1.69%,respectively.3,Four narrow bandgap D-A copolymers,P1,P2,P3,and P4 containing benzo-dithiophene-dione and naphtha-thiophene-dione were desgined and synthesized.We found that the absorption and photovoltaic performance of the ben-dithiophene-dione based polymers are better than the naphtho-thiophene-dione based polymers,because the quinone structure from ben-dithiophene-dione unit is more stable,leading to the higher degree of molecular reqularity,better molecular packing,and higher charge mobility,which are benefit for the photovoltaic performance.Besides,among all of polymers,P2 showed the best PCE beause of the better solubility and coplanarity from the branched chains.The solar cells using P1,P2,P3,and P4 as donor material and PC71BM as acceptor material showed the PCE vaules of 4.83%,5.72%,4.23%,and 4.41%,respectively.