Synthesis And Optoeiectronic Properties Of Polymer Donors With An Asymmetric Unit Of Fluoridated Thiophene-phenylene

Bulk heterojunction?BHJ?polymer solar cells?PSCs?have attracted extensive attention because of their advantages of low processing cost,light weight and mechanical flexibility.The progress on the design and synthesis of donor polymers and acceptor materials along with the development of novel device architectures and morphology control methods has led to the dramatic enhancement of the power conversion efficiency?PCE?of BHJ PSCs.Among these factors,the properties of semiconducting polymers play determining roles.Based on asymmetric unit synthesis of donor materials,the structural unit arrangement of polymer molecules is different,making the materials have excellent properties.In this dissertation,we have carried out the following works:?1?In Chapter 3,two low bandgap copolymers?PDPP-PT and PDPP-PTF₂?based on asymmetrical phenylene-thiophene?PT?or fluoridated phenylene-thiophene?PTF₂?as donor unit and DPP as acceptor unit were designed,synthesized and applied in PSCs.As expected,both polymers exhibited broad absorption spectrum,covering the spectral range from 350 nm up to 900 nm.The DPP-based polymers show the relatively narrows 1.5 eV and 1.4 e V for PDPP-PT and PDPP-PTF₂,respectively,which potentially render them qualified as electron donors in PSCs.The polymer PDPP-PTF₂ with asymmetric PTF2 exhibits the highest PCE of 3.0%with a Voc of 0.68 V and a Jsc of 7.24 mA cm^-2.In addition,we found that the polymer PDPP-PTF₂with a smaller dihedral angle between thiophene and fluoridated phenylene of the asymmetrical PTF₂ moiety could form better blending morphology with PC₇₀BM.?2?In Chapter 4,there random copolymers?PBDT-PT-DPP?PBDT-PTF-DPP and PBDT-PTF₂-DPP?based on asymmetrical phenylene-thiophene?PT??mono fluoridated phenylene-thiophene?PTF?or difluoridated phenylene-thiophene PTF₂ as donor unit were designed and synthesized.There polymers have borad absorption spectrum?350⁸00 nm?and the narrow optical band gaps?1.55-1.57 eV?.The introduction of the strong electron-withdrawing fluorine onto backbone of conjugated polymer has been proven to be an effective method to reducemolecularorbitalsenergylevels.ThePCEof PBDT-PT-DPP:PC60BM,PBDT-PTF-DPP:PC60BMand PBDT-PTF₂-DPP:PC60BM devices are 1.22%,1.07%and 1.78%,respectively.?3?In Chapter 5,two thienopyrrolodione copolymers?PTPD-PT and PTPD-PTF₂?based on asymmetrical phenylene-thiophene?PT?or fluoridated phenylene-thiophene?PTF₂?as donor unit were designed and synthesized.PTPD-PT and PTPD-PTF₂ exhibited good thermal stability for 5%weight loss at 385°C and 397°C,respectively.Both polymers exhibit a absorption ranger from 350 to 620 nm and belong to donor materials with narrow absorption and wide gap.The HOMO level of PTPD-PT and PTPD-PTF₂ are-5.55 and-5.53 eV,respectively,which match with the energy levels of fullerene.The two poymers are suitable for the preparation of PSCs as donor materials.