Singlet fission is a spin-allowed process by which two non-interacting triplet excitons are generated from a singlet exciton. This type of multiexciton generation mechanism may have the potential to overcome the Shockley-Queisser limit and could enable the development of more efficient solar cells. In this contribution, we analyze intramolecular singlet fission in two modified pentacene dimers covalently bonded to a xanthene spacer employing density functional theory and multireference perturbation theory methods. The systems investigated differ in the electronic structure and bulkiness of the substituents used and in this work we analyze the impact that these aspects have in the relative contributions of the direct and mediated mechanisms to the intramolecular singlet fission.

单重态裂变是自旋允许的过程，通过该过程，单重态激子会生成两个非相互作用的三重态激子。这种类型的多激子产生机制可能具有克服Shockley-Queisser限制的潜力，并且可能使开发更高效的太阳能电池成为可能。在这项贡献中，我们使用密度泛函理论和多参考扰动理论方法分析了共价键合于x吨间隔基的两个修饰的并五苯二聚体中的分子内单峰裂变。所研究的系统在电子结构和所用取代基的体积方面存在差异，在这项工作中，我们分析了这些方面对分子内单线态裂变的直接和介导机制的相对贡献的影响。