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Abstract：
Semiconducting conjugated polymers (CPs) are pivotal in advancing organic electronics, offering tunable properties for solar cells and field-effect transistors. Here, we carry out first-principle calculations to study individual cis-polyacetylene (cis-PA) oligomers and their ensembles. The ground electronic structures are obtained using density functional theory (DFT), and excited state dynamics are explored by computing nonadiabatic couplings (NACs) between electronic and nuclear degrees of freedom. We compute the nonradiative relaxation of charge carriers and photoluminescence (PL) using the Redfield theory. Our findings show that electrons relax faster than holes. The ensemble of oligomers shows faster relaxation compared to the single oligomer. The calculated PL spectra show features from both interband and intraband transitions. The ensemble shows broader line widths, redshift of transition energies, and lower intensities compared to the single oligomer. This comparative study suggests that the dispersion forces and orbital hybridizations between chains are the leading contributors to the variation in PL. It provides insights into the fundamental behaviors of CPs and the molecular-level understanding for the design of more efficient optoelectronic devices.
摘要：
半导体共轭聚合物(CP)在推进有机电子学方面至关重要，为太阳能电池和场效应晶体管提供可调谐的性能。这里,我们进行第一原理计算以研究单个顺式聚乙炔（cis-PA）低聚物及其集合。使用密度泛函理论（DFT）获得接地电子结构，通过计算电子和核自由度之间的非绝热耦合（NAC）来探索激发态动力学。我们使用Redfield理论计算电荷载流子和光致发光（PL）的非辐射弛豫。我们的发现表明电子比空穴弛豫得更快。与单一低聚物相比,低聚物的集合显示更快的松弛。计算的PL光谱显示了来自带间和带内跃迁的特征。合奏显示更宽的线宽，跃迁能量的红移，和较低的强度相比，单一的低聚物。这项比较研究表明，链之间的分散力和轨道杂交是PL变化的主要原因。它提供了对CP的基本行为和分子水平理解的见解，以设计更有效的光电器件。
