Pavithrakumar M, Krishnan S, Senthilkumar K
Department of Physics, Bharathiar University, Coimbatore-641 046, India.
J Phys Chem A. 2021 May 13;125(18):3852-3862. doi: 10.1021/acs.jpca.1c00790. Epub 2021 May 3.
Structure, optical absorption, and charge transport properties of dibenzocoronene tetracarboxdiimide (DCDI) based molecules were studied using electronic structure calculations. Based on the optimized neutral, cationic, and anionic geometries the ionized state properties, such as ionization potential, electron affinity, hole extraction potential, electron extraction potentials, and reorganization energy, were calculated. On the basis of the ground state geometry of the studied molecules, the absorption spectra were calculated using the time-dependent density functional theory (TDDFT) method at the PBE0/def-TZVP level of theory. It has been observed that the substitution of different functional groups significantly alters the absorption spectra of DCDI. The methoxy- (OCH-) substituted DCDI molecule has a maximum absorption wavelength of 529 nm. The charge transport parameters, such as the charge transfer integral, spatial overlap integral, and the site energy, are calculated directly from the Kohn-Sham matrix elements. The reorganization energy for the presence of excess positive and negative charges and the charge transfer rate calculated from Marcus' theory were used to find the mobility of charge carriers. The computed results show that the mobility of charge carriers is strongly influenced by the functional groups present on the DCDI molecule. The effect of intermolecular structural fluctuations on charge transport properties was studied through molecular dynamics and Monte Carlo simulations based on the polaron hopping mechanism. The calculated charge carrier mobility shows that the cyano- (CN-) substituted DCDI molecules are having n-type semiconducting property while, methoxy- (OCH-) and thiol- (SH-) substituted DCDI molecules exhibit ambipolar semiconducting properties.
利用电子结构计算研究了基于二苯并蔻四羧酸二亚胺（DCDI）的分子的结构、光吸收和电荷传输性质。基于优化后的中性、阳离子和阴离子几何结构，计算了电离态性质，如电离势、电子亲和势、空穴提取势、电子提取势和重组能。基于所研究分子的基态几何结构，使用含时密度泛函理论（TDDFT）方法在PBE0/def-TZVP理论水平下计算了吸收光谱。已观察到不同官能团的取代显著改变了DCDI的吸收光谱。甲氧基（OCH-）取代的DCDI分子的最大吸收波长为529 nm。电荷传输参数，如电荷转移积分、空间重叠积分和位能，直接从Kohn-Sham矩阵元计算得出。利用存在过量正电荷和负电荷时的重组能以及根据Marcus理论计算的电荷转移速率来确定电荷载流子的迁移率。计算结果表明，电荷载流子的迁移率受到DCDI分子上存在的官能团的强烈影响。基于极化子跳跃机制，通过分子动力学和蒙特卡罗模拟研究了分子间结构波动对电荷传输性质的影响。计算得到的电荷载流子迁移率表明，氰基（CN-）取代的DCDI分子具有n型半导体性质，而甲氧基（OCH-）和硫醇基（SH-）取代的DCDI分子表现出双极性半导体性质。
