Sarkar Ritabrata, Habib Md, Pal Sougata
Department of Chemistry, University of Gour Banga, Malda 732103, India.
Bremen Center for Computational Materials Science, Universität Bremen, Bremen 28359, Germany.
J Phys Chem Lett. 2022 Aug 11;13(31):7213-7219. doi: 10.1021/acs.jpclett.2c02073. Epub 2022 Jul 30.
Macromolecular porphyrin nanorings are receiving significant attention because of their excellent optoelectronic properties. However, their efficiencies as potential solar materials are significantly affected by nonradiative charge recombination. To understand the recombination mechanism by alternating structural parameters and using tight-binding nonadiabatic molecular dynamics, we demonstrate that charge recombination depends strongly on the mode of the linker in the porphyrin nanoring. The nanoring having all-butadiyne-linkage (pristine-P8) inhibits carrier relaxation. In contrast, a partially fused nanoring (fused-P8) expedites the rate of quantum transition. An extension of the lifetime by a factor of 4 is due to the larger optical gap in pristine-P8 that reduces the NA coupling by decreasing the overlap between band edge states. Additionally, an intense phonon peak in the low-frequency region and rapid coherence loss within the electronic subsystem favors prolonging the carrier lifetime. This study provides an atomistic realization for the design of macromolecular porphyrin nanorings for the potential use in photovoltaic materials.
大分子卟啉纳米环因其优异的光电特性而备受关注。然而，它们作为潜在太阳能材料的效率受到非辐射电荷复合的显著影响。为了通过改变结构参数并利用紧束缚非绝热分子动力学来理解复合机制，我们证明电荷复合强烈依赖于卟啉纳米环中连接体的模式。具有全丁二炔连接的纳米环（原始-P8）抑制载流子弛豫。相比之下，部分融合的纳米环（融合-P8）加快了量子跃迁速率。寿命延长4倍是由于原始-P8中较大的光学带隙通过减少带边态之间的重叠降低了非绝热耦合。此外，低频区域强烈的声子峰以及电子子系统内快速的相干损耗有利于延长载流子寿命。这项研究为设计可用于光伏材料的大分子卟啉纳米环提供了原子层面的认识。
