Riley Drew B, Meredith Paul, Armin Ardalan, Sandberg Oskar J
Sustainable Advanced Materials Programme (Sêr SAM), Department of Physics, Swansea University, Singleton Park, Swansea SA2 8PP, United Kingdom.
J Phys Chem Lett. 2022 May 26;13(20):4402-4409. doi: 10.1021/acs.jpclett.2c00791. Epub 2022 May 12.
Despite general agreement that the generation of free charges in organic solar cells is driven by an energetic offset, power conversion efficiencies have been improved using low-offset blends. In this work, we explore the interconnected roles that exciton diffusion and lifetime play in the charge generation process under various energetic offsets. A detailed balance approach is used to develop an analytic framework for exciton dissociation and free-charge generation accounting for exciton diffusion to and dissociation at the donor-acceptor interface. For low-offset systems, we find the exciton lifetime to be a pivotal component in the charge generation process, as it influences both the exciton and CT state dissociation. These findings suggest that any novel low-offset material combination must have long diffusion lengths with long exciton lifetimes to achieve optimum charge generation yields.
尽管人们普遍认为有机太阳能电池中自由电荷的产生是由能量偏移驱动的，但使用低偏移混合材料提高了功率转换效率。在这项工作中，我们探讨了在各种能量偏移下激子扩散和寿命在电荷产生过程中所起的相互关联的作用。采用详细平衡方法来开发一个用于激子解离和自由电荷产生的分析框架，该框架考虑了激子向供体-受体界面的扩散以及在该界面处的解离。对于低偏移系统，我们发现激子寿命是电荷产生过程中的一个关键因素，因为它影响激子和电荷转移（CT）态的解离。这些发现表明，任何新型的低偏移材料组合都必须具有长扩散长度和长激子寿命，以实现最佳的电荷产生效率。
