Saes Bart W H, Wienk Martijn M, Janssen René A J
Molecular Materials and Nanosystems and Institute for, Complex Molecular Systems, Eindhoven University of Technology, 5600, MB, Eindhoven, The Netherlands.
Dutch Institute for Fundamental Energy Research, De Zaale 20, 5612, AJ, Eindhoven, The Netherlands.
Chemistry. 2020 Nov 6;26(62):14221-14228. doi: 10.1002/chem.202001722. Epub 2020 Sep 29.
Introducing solubilizing α-branched alkyl chains on a poly(diketopyrrolopyrrole-alt-terthiophene) results in a dramatic change of the structural, optical, and electronic properties compared to the isomeric polymer carrying β-branched alkyl side chains. When branched at the α-position the alkyl substituent creates a steric hindrance that reduces the tendency of the polymer to π-π stack and endows the material with a much higher solubility in common organic solvents. The wider π-π stacking and reduced tendency to crystallize, evidenced from grazing-incidence wide-angle X-ray scattering, result in a wider optical band gap in the solid state. In solar cells with a fullerene acceptor, the α-branched isomer affords a higher open-circuit voltage, but an overall lower power conversion efficiency as a result of a too well-mixed nanomorphology. Due its reduced π-π stacking, the α-branched isomer fluoresces and affords near-infrared light-emitting diodes emitting at 820 nm.
与带有β-支链烷基侧链的异构聚合物相比，在聚（二酮吡咯并吡咯-alt-对三联苯）上引入增溶α-支链烷基链会导致结构、光学和电子性质发生显著变化。当烷基取代基在α位分支时，会产生空间位阻，降低聚合物π-π堆积的倾向，并使该材料在常见有机溶剂中的溶解度更高。掠入射广角X射线散射表明，更宽的π-π堆积和更低的结晶倾向导致固态下具有更宽的光学带隙。在具有富勒烯受体的太阳能电池中，α-支链异构体提供了更高的开路电压，但由于纳米形貌混合过于良好，导致整体功率转换效率较低。由于其π-π堆积减少，α-支链异构体发出荧光，并提供发射波长为820 nm的近红外发光二极管。
