Giri Geetanjali, Pati Y Anusooya, Ramasesha S
Solid State and Structural Chemistry Unit , Indian Institute of Science , Bangalore 560012 , India.
J Phys Chem A. 2019 Jun 27;123(25):5257-5265. doi: 10.1021/acs.jpca.9b02196. Epub 2019 Jun 13.
In recent years, polycyclic aromatic hydrocarbons (PAHs) have been studied for their electronic properties as they are viewed as nanodots of graphene. They have also been of interest as functional molecules for applications such as light-emitting diodes and solar cells. Since the last few years, varying structural and chemical properties corresponding to the size and geometry of these molecules have been studied both theoretically and experimentally. Here, we carry out a systematic study of the electronic states of several PAHs using the Pariser-Parr-Pople model, which incorporates long-range electron correlations. In all of the molecules studied by us, we find that the 2A state is below the 1B state and hence none of them will be fluorescent in the gaseous phase. The singlet-triplet gap is more than half of the singlet-singlet gap in all cases, and hence, none of these PAHs can be candidates for improved solar cell efficiencies in a singlet fission. We discuss in detail the properties of the electronic states, which include bond orders and spin densities (in triplets) of these systems.
近年来，多环芳烃（PAHs）因其被视为石墨烯的纳米点而对其电子性质展开了研究。它们作为发光二极管和太阳能电池等应用的功能分子也备受关注。在过去几年中，对应于这些分子大小和几何形状的不同结构和化学性质已在理论和实验上进行了研究。在此，我们使用包含长程电子相关性的帕里泽 - 帕尔 - 波普尔模型对几种多环芳烃的电子态进行了系统研究。在我们研究的所有分子中，我们发现2A态低于1B态，因此它们在气相中均不会发荧光。在所有情况下，单重态 - 三重态能隙超过单重态 - 单重态能隙的一半，因此，这些多环芳烃中没有一种可作为通过单重态裂变提高太阳能电池效率的候选材料。我们详细讨论了这些系统电子态的性质，其中包括键级和（三重态中的）自旋密度。
