The Synthesis Of Novel WBG Polymer Donors And Application In Organic Solar Cells

As the most important energy source at present,petroleum,being highly polluting and non-renewable,it is urgent to find a new clean energy to replace it.Among a series of new energy sources,solar energy has become the most satisfying alternative due to its cleanliness and sustainable use.Organic solar cells convert solar energy into electrical energy,the material of its internal active layer is usually composed of two parts:acceptors and donors.The addition of wide band gap polymer donors into the active layer could increase the open circuit voltage of the battery.At the same time,it will form a three-dimensional network interpenetrating structure after being blended with the small molecule acceptor.This structure can effectively improve the battery Medium carrier transmission capacity.At present,there are few high-efficiency wide-bandgap polymer donor materials,and most of them are relatively expensive.Based on this,the article chooses a cheaper substrate and designs a possibly high-efficiency structure from the perspective of cost and efficiency.Several wide band gap polymer donor materials were synthesized with several synthesis steps,and the correctness of the structure was confirmed by hydrogen nuclear magnetic resonance spectrum,carbon nuclear magnetic resonance spectrum,and mass spectrum,then matched with suitable receptors to prepare batteries.Finally,a series of characterizations were carried out on the donors and the battery.The main research works and results are as follows:(1)Donors W4(ortho substitution)and W5(para substitution)with fluorine and alkoxy substituted benzene(FAB)units as the core were synthesized,and this section systematically studied the influence of different positions on the photovoltaic performance of the battery.The results shown that the introduction of the electron withdrawing group F atom can reduce the energy level of the material,the introduction of the alkyl chain made the solubility of the polymer molecule adjustable,and the O atom can form a non-covalent bond with the S atom on the thiophene,increasing the rigidity and planarity of the entire molecule.Both W4 and W5 had obvious intermolecular interactions and high short-circuit currents(>25 m A cm^-2),but the carrier mobility was higher and more balanced,the proportion of bimolecular recombination was lower when the ortho position is replaced,W4:Y6 battery had a better morphology,resulting its fill factor was higher.The final W4:Y6 and W5:Y6 battery efficiencies reached 15.25%and13.00%,respectively.(2)Donor W6 with dithienodione isoindole(DTDOII)unit as the core was synthesized,and this section systematically studied the influence of photovoltaic performance of the cells while W6 matched with two small molecule acceptors with different band gaps.The results shown that the introduction of electron withdrawing group DOII reduced the energy level of W6,methylation prevent the excessive aggregation of conjugate planes,and W6 has suitable planarity.The cells were made with the ultra-narrow band gap acceptor N3 and the narrow band gap acceptor IT-4F,respectively.The open circuit voltages were both high,reaching 0.91V and 0.95V,respectively.The short-circuit current of the W6:N3 cell was 24.69 m A cm^-2,which was far Higher than W6:IT-4F cell,W6:N3 cell's carrier mobility was higher and more balanced,the proportion of bimolecular recombination was lower,but it's active layer morphology was not good,resulting the fill factor of two cells were almostly same.In the end,W6:N3 and W6:IT-4F cells obtained conversion efficiencies of 14.54%and 12.47%,respectively.