Hohgardt Manuel, Gädeke Franka Elisabeth, Wegener Lucas, Walla Peter Jomo
Department for Biophysical Chemistry, Institute for Physical and Theoretical Chemistry, Technische Universität Braunschweig, 38106 Braunschweig, Germany.
Polymers (Basel). 2022 Jan 28;14(3):532. doi: 10.3390/polym14030532.
Light-harvesting concentrators have a high potential to make highly efficient but precious energy converters, such as multijunction photovoltaics, more affordable for everyday applications. They collect sunlight, including diffusively scattered light, on large areas and redirect it to much smaller areas of the highly efficiency solar cells. Among the best current concepts are pools of randomly oriented light-collecting donor molecules that transfer all excitons to few aligned acceptors reemitting the light in the direction of the photovoltaics. So far, this system has only been realized for the 350-550 nm wavelength range, suitable for AlGaInP photovoltaics. This was achieved by using acceptor molecules that aligned during mechanical stretching of polymers together with donors, that stay random in that very same material and procedure. However, until recently, very little was known about the factors that are responsible for the alignability of molecules in stretched polymers and therefore it was difficult to find suitable donors and acceptors, as well as for other spectral ranges. Recently, a structural parameter was introduced with a high predictivity for the alignability of molecules that contain rigid band-like structures or linear aromatic π-systems. However, for light concentrators in more red spectral ranges, molecular systems often contain larger and extended, planar-like π-systems for which the previously reported parameter is not directly applicable. Here, we present a refined prediction parameter also suitable for larger plane-like structures. The new parameter depends on the number of in-plane atoms divided by out-of-plane atoms as determined by computational geometry optimization and additionally the planar aspect ratio for molecules that contain only in-plane atoms. With the help of this parameter, we found a new system that can efficiently collect and redirect light for the second 500-700 nm AlGaAs layer of current world-record multijunction photovoltaics. Similarly, as the previously reported system for the blue-green layer, it has also overall absorption and re-directioning quantum efficiencies close to 80-100%. Both layers, together, already cover about 75% of the energy in the solar spectrum.
光收集聚光器具有很大潜力，可使高效但昂贵的能量转换器（如多结光伏电池）在日常应用中更具成本效益。它们在大面积上收集阳光，包括漫散射光，并将其重新导向高效太阳能电池的小得多的区域。目前最好的概念之一是随机取向的光收集供体分子池，这些分子将所有激子转移到少数排列的受体上，然后沿光伏方向重新发射光。到目前为止，该系统仅在350 - 550纳米波长范围内实现，适用于AlGaInP光伏电池。这是通过在聚合物机械拉伸过程中使受体分子与供体分子排列在一起实现的，供体分子在相同材料和过程中保持随机状态。然而，直到最近，对于拉伸聚合物中分子可排列性的影响因素知之甚少，因此很难找到合适的供体和受体，以及适用于其他光谱范围的材料。最近，引入了一个对包含刚性带状结构或线性芳香π体系的分子可排列性具有高预测性的结构参数。然而，对于更红光谱范围内的光聚光器，分子系统通常包含更大、更扩展的平面状π体系，先前报道的参数并不直接适用。在此，我们提出了一个也适用于更大平面状结构的改进预测参数。新参数取决于通过计算几何优化确定的面内原子数与面外原子数之比，此外还取决于仅包含面内原子的分子的平面纵横比。借助这个参数，我们发现了一种新系统，它可以有效地收集并重新导向当前世界纪录多结光伏电池的第二个500 - 700纳米AlGaAs层的光。同样，与先前报道的蓝绿层系统一样，它的整体吸收和重新导向量子效率也接近80 - 100%。这两层合起来已经覆盖了太阳光谱中约75%的能量。
