Morvillo P
ENEA, C.R. Portici, UTTP-NANO, Piazzale E Fermi 1, 80055 Portici (NA), Italy.
J Nanosci Nanotechnol. 2013 Jul;13(7):5221-6. doi: 10.1166/jnn.2013.7512.
In the present study, quantum chemical methods were applied to investigate the energy levels of the frontier orbital of mono and multi adducts of diphenylmethanofullerenes (DPMs). Recently these molecules have been used as electron acceptors in polymer solar cells showing interesting properties compared to the widely used [6, 6]-phenyl-C61-butyric acid methyl ester (PCBM). The geometries of all the investigated compounds were optimized with the density functional theory at the B3LYP/3-21G level of calculation. We studied the effect of electron-donating (methoxy and methyl thioether) and electron-withdrawing (fluorine) substituents (placed on the diphenylmethano addend in ortho, meta and para position of the phenyl rings), on the lowest unoccupied molecular orbital (LUMO) level of DPM. Afterward, we analysed all the possible isomers arising from bis and tris additions to fullerene cage. The LUMO level is significantly raised compared to the mono adduct but different isomers have different LUMO levels. Since the open circuit voltage (V(oc)) for polymer solar cells with ohmic contacts is proportional to the difference between the highest occupied molecular orbital (HOMO) of the donor polymer and the LUMO of the acceptor (fullerene), these bisadducts have the potential to increase the V(oc) of the corresponding devices.
在本研究中，应用量子化学方法研究了二苯基甲烷富勒烯（DPMs）单加合物和多加合物的前线轨道能级。最近，这些分子已被用作聚合物太阳能电池中的电子受体，与广泛使用的[6,6]-苯基-C61-丁酸甲酯（PCBM）相比，显示出有趣的特性。所有研究化合物的几何结构都在密度泛函理论的B3LYP/3-21G计算水平上进行了优化。我们研究了给电子基团（甲氧基和甲硫醚）和吸电子基团（氟）取代基（位于苯环邻位、间位和对位的二苯基甲烷加合物上）对DPM最低未占分子轨道（LUMO）能级的影响。之后，我们分析了富勒烯笼双加成和三加成产生的所有可能异构体。与单加合物相比，LUMO能级显著提高，但不同异构体具有不同的LUMO能级。由于具有欧姆接触的聚合物太阳能电池的开路电压（V(oc)）与供体聚合物的最高占据分子轨道（HOMO）和受体（富勒烯）的LUMO之间的差值成正比，这些双加合物有可能提高相应器件的V(oc)。
