基于二噻吩并吡咯π桥的窄带隙非富勒烯受体材料在有机太阳能电池中的应用

Near-infrared Absorbing Non-fullerene Acceptors with Dithienopyrrole as π Spacer for Organic Solar Cells

以不同烷基取代的二噻吩并吡咯(DTP)为π桥,连接吲哒省并二噻吩(IDT)中间单元和氰基茚酮(IC)或二氟代氰基茚酮(2F-IC)末端基团,设计并合成了6个窄带隙的非富勒烯受体材料。其中,IDTDTP-C2C2-H和IDTDTP-C2C2-F中的DTP单元以1-乙基丙基为侧链,IDTDTP-C6C6-H和IDTDTP-C6C6-F中的DTP单元以1-己基庚基为侧链,IDTDTP-C12-H和IDTDTP-C12-F中的DTP单元以十二烷基为侧链。6个分子均具有较窄的光学带隙(1.37~1.44 eV)。相比于以IC为末端基团的分子(IDTDTP-C2C2-H、IDTDTP-C6C6-H和IDTDTP-C12-H),由于氟原子的拉电子效应,以2F-IC为末端基团的分子(IDTDTP-C2C2-F、IDTDTP-C6C6-F和IDTDTP-C12-F)具有红移的吸收光谱,以及更低的最高分子占有轨道能级(HOMO)和最低分子空轨道(LUMO)能级。以宽带隙聚合物聚[2,6-(4,8-双(5-(2-乙基己基))噻吩-2-基)-苯并[1,2-b:4,5-b′]二噻吩-alt-5,5-(1′,3′-二-2-噻吩)-5′,7′-双(2-乙基己基)-苯并[1′,2′-c:4′,5′-c′]二噻吩-4,8-二酮](PBDB-T)为给体材料,制备了有机太阳能电池器件。PBDB-T:IDTDTP-C6C6-F共混薄膜具有较高且更平衡的空穴/电子迁移率,以及良好的形貌,基于PBDB-T:IDTDTP-C6C6-F的有机太阳能电池获得了6.94%的能量转换效率,开路电压为0.86 V,短路电流密度为13.56 mA/cm 2,填充因子为59.5%。

A series of non-fullerene acceptors with dithieno[3,2-b:2′,3′-d]pyrrole(DTP)πbridge to link indacenodithiophene(IDT)core and 3-(dicyanomethylidene)indan-1-one(IC)or difluorinated IC(2F-IC)terminals,i.e.IDTDTP-C2C2-H and IDTDTP-C2C2-F with 1-ethylpropyl on DTP,IDTDTP-C6C6-H and IDTDTP-C6C6-F with 1-hexylheptyl on DTP,and IDTDTP-C12-H and IDTDTP-C12-F with n-dodecyl on DTP,was designed and synthesized.These molecules achieved low optical band gaps(1.37~1.44 eV).Compared with the IC-terminated molecules(IDTDTP-C2C2-H,IDTDTP-C6C6-H and IDTDTP-C12-H),IDTDTP-C2C2-F,IDTDTP-C6C6-F and IDTDTP-C12-F with 2F-IC as terminals show red-shifted absorption spectra and down-shifted the highest occupied molecular orbitals(HOMO)and the lowest unoccupied molecular orbitals(LUMO)energy levels owing to the electron-withdrawing ability of F substituents.Organic solar cells(OSCs)based on these acceptors were fabricated with the wide-bandgap polymer poly[2,6-(4,8-bis(5-(2-ethylhexyl))thiophen-2-yl)-benzo[1,2-b:4,5-b′]dithiophene-alt-5,5-(1′,3′-di-2-thienyl)-5′,7′-bis(2-ethylhexyl)-benzo[1′,2′-c:4′,5′-c′]dithiophene-4,8-dione](PBDB-T)as the donor.Owing to the higher and more balanced hole and electron mobilities,and a proper phase-separated morphology in the blend film,IDTDTP-C6C6-F with 1-hexylheptyl on DTP unit achieved a maximum power conversion efficiency(PCE)of 6.94%with an open-circuit voltage(V oc)of 0.86 V,a short circuit current density(J sc)of 13.56 mA/cm 2 and a fill factor(FF)of 59.5%.