Keya Kamrun N, Han Yulun, Xia Wenjie, Kilin Dmitri
Department of Aerospace Engineering, Iowa State University, Ames, IA 50011, USA.
Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND 58108, USA.
Polymers (Basel). 2024 Jul 2;16(13):1896. doi: 10.3390/polym16131896.
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.
半导体共轭聚合物（CPs）在推动有机电子学发展方面起着关键作用，为太阳能电池和场效应晶体管提供了可调节的性能。在此，我们进行第一性原理计算以研究单个顺式聚乙炔（cis-PA）低聚物及其聚集体。利用密度泛函理论（DFT）获得基态电子结构，并通过计算电子与核自由度之间的非绝热耦合（NACs）来探索激发态动力学。我们使用雷德菲尔德理论计算电荷载流子的非辐射弛豫和光致发光（PL）。我们的研究结果表明，电子的弛豫速度比空穴快。与单个低聚物相比，低聚物聚集体表现出更快的弛豫。计算得到的PL光谱显示了带间和带内跃迁的特征。与单个低聚物相比，聚集体显示出更宽的线宽、跃迁能量的红移和更低的强度。这项对比研究表明，链间的色散力和轨道杂化是PL变化的主要因素。它为CPs的基本行为提供了见解，并为设计更高效的光电器件提供了分子水平的理解。
