Design,Synthesis And Photovoltaic Performances Of Novel Active Layer Materials Containing Triazole And Imide Units

The development of new clean energy has become a focus of general attention all over the world.Solar energy has become one of the most widely used clean energy sources in human society due to its advantages of universal,harmless,large,long-lasting and so on.As one of the effective ways to utilize solar energy,polymer solar cells have gained widespread attention in scientific research and industry due to their advantages of low cost,light weight,flexibility,solution processing and large-area printing preparation.So far,the power conversion efficiency of polymer solar cells has exceeded 18%.The continuous breakthroughs in the power conversion efficiency of polymer solar cells are mainly attributed to the innovation of new materials.In particular,the development of active layer materials is the key to the great achievements of polymer solar cells.This paper is dedicated to developing new active layer materials,focusing on triazole and imide structural units,inventing a number of new structural units for material construction,designing and synthesizing multiple types of polymer donors and small molecules acceptor materials,systematically studied the influence of the structure of the active layer material on its physical and chemical properties and photovoltaic properties,and prepared a series of high-efficiency polymer solar cells based on these synthesized active layer materials.In the second chapter of this paper,I have synthesized two kinds of donor-acceptors（D-A）type conjugated polymer donor materials（PBTZNT and PFBTZNT）,which containing without fluorine or fluorine substituted side chains,by using naphtho[1,2-d:5,6-d’]bis（[1,2,3]triazole）（TZNT）as the electron-withdrawing unit and benzodithiophene（BDT）as the electron-donating unit.The effect of the TZNT units and fluorine atoms on the physical and chemical properties of the polymer donors has been systematically studied.At the same time,the polymer donor materials were blended with the small molecule acceptor m-ITIC to fabricate bulk heterojunction polymer solar cells,and the relationship between the molecular structure of the material and the photovoltaic performance of the device has been studied.The results show that PFBTZNT has a better absorption spectrum and a deeper electrochemical energy level than that of PBTZNT.The power conversion efficiency of the polymer solar cell devices based on PFBTZNT exceeds 11%.The V_OC,J_SC and FF of the devices based on PFBTZNT which containing fluorine substitution side chains surpass that of devices based on PBTZNT which containing non-fluorine side chain.In Chapter 3 of this paper,I optimized the alkyl chain of TZNT-based polymers,which effectively reduced the difficulty of synthesis and increased the reaction yield.Using naphthotriazole as the electron-withdrawing unit and 2,5-thienyl-1,4-difluorobenzene or 3,6-dithienyl-1,2-difluorobenzene as the electron-donating unit with different fluorination positions,we synthesized two different D-A type polymer donors（P-pff B-TZNT and P-off B-TZNT）.The influence of fluorination positions of the electron-donating units on the physical and chemical properties of polymers was systematically studied,and those polymers were applied to non-fullerene polymer solar cells to study their photovoltaic performance.The results show that P-pff B-TZNT containing 1,4-difluorobenzene units has stronger aggregation and better crystallization properties than that of P-off B-TZNT containing 1,2-difluorobenzene units.The power conversion efficiency of the polymer solar cell based on P-pff B-TZNT:ITIC is 9.17%,and the power conversion efficiency of the polymer solar cell based on P-off B-TZNT:ITIC is6.72%.Due to the polymer P-pff B-TZNT 1,4-difluorobenzene units has better intermolecular interaction than that of P-off B-TZNT,the device fabricated from P-pff B-TZNT has higher J_SCand FF.In Chapter 4 of this paper,I introduce perylene diimide（PDI）unit into fused ring electron acceptors（FREAs）,developed a new type of electron-donating center core structure,which is a structure of a PDI fused with two dithieno[3,2-b:2’,3’-d]pyrroles.Connecting 3-（dicyanomethylidene）indan-1-one and 2-（6-Oxo-5,6-dihydro-4H-cyclopenta[c]thiophen-4-ylidene）malononitrile to the two ends of this central core,respectively,two small molecule acceptor materials with different end groups,PP-4F and PP-4Cl,were synthesized.The physical and chemical properties of two small molecules conducted has been research,and the two small molecules were blended with the polymer donor PBDB-T,fabricated polymer solar cells to study their photovoltaic performance.I found that these two small molecules showed strong and wide-range absorption in the visible light region.The PPIC-based polymer solar cell achieved a power conversion efficiency of 8.67%,and the PPCC-based polymer solar cell achieved a power conversion efficiency of 8.24%.In Chapter 5 of this paper,I continue to introduce PDI into Y6 series fused-ring molecules.I fused two PDI at both ends of the central core of the Y6 series molecule with an electron-deficient structure,synthesized two fully fused small molecule acceptor materials with different alkyl chain lengths,FPB-BO and FPB-HD.the physical and chemical properties of two small molecules and the photovoltaic performance of the polymer solar cells fabricated from those two small molecules has been studied.Both two small molecules FPB-BO and FPB-HD exhibit a very high LUMO energy level.The polymer donor PBDB-T were selected to blend with two small molecules,respectively,both two devices fabricated from the acceptor can obtain a power conversion efficiency of more than 6%.In Chapter 6 of this paper,I introduced the naphthalene diimide（NDI）unit into the non-fused ring small molecule acceptor.Two non-fused ring small molecule acceptor materials were synthesized by using the structure of NDI coupling two cyclopenta[2,1,b-:3,4,b’]dithiophenes as the electron-donating center core,and 2-（5,6-difluoro-3-oxo-2,3-dihydro-1H-inden-1-ylidene）malononitrile or 5,6-dichloro-3-（dicyanomethylidene）fluorenone as end group.the physical and chemical properties of two small molecules and the photovoltaic performance of the polymer solar cell devices based on those two small molecules were systematic studied.both small molecules exhibit excellent absorption properties and excellent crystallinity.PM6was selected as the donor to be blended with small molecules NP-4F and NP-4Cl to fabricate polymer solar cells.The device based on PM6:NP-4F obtained an efficiency of 7.97%,and the device based on PM6:NP-4Cl obtained an efficiency of 7.64%.