Wong Bryan M, Cordaro Joseph G
Materials Chemistry Department, Sandia National Laboratories, Livermore, California 94551, USA.
J Chem Phys. 2008 Dec 7;129(21):214703. doi: 10.1063/1.3025924.
The excited-state properties in a series of coumarin solar cell dyes are investigated with a long-range-corrected (LC) functional which asymptotically incorporates Hartree-Fock exchange. Using time-dependent density functional theory (TDDFT), we calculate excitation energies, oscillator strengths, and excited-state dipole moments in each of the dyes as a function of the range-separation parameter mu. To investigate the acceptable range of mu and to assess the quality of the LC-TDDFT formalism, an extensive comparison is made between LC-BLYP excitation energies and approximate coupled-cluster singles and doubles calculations. When using a properly optimized value of mu, we find that the LC technique provides a consistent picture of charge-transfer excitations as a function of molecular size. In contrast, we find that the widely used B3LYP hybrid functional severely overestimates excited-state dipole moments and underestimates vertical excitation energies, especially for larger dye molecules. The results of the present study emphasize the importance of long-range exchange corrections in TDDFT for investigating the excited-state properties in solar cell dyes.
利用一种渐近包含哈特里-福克交换的长程校正（LC）泛函，研究了一系列香豆素太阳能电池染料的激发态性质。采用含时密度泛函理论（TDDFT），我们计算了每种染料的激发能、振子强度和激发态偶极矩，它们都是范围分离参数μ的函数。为了研究μ的可接受范围并评估LC-TDDFT形式体系的质量，我们对LC-BLYP激发能与近似耦合簇单双激发计算进行了广泛比较。当使用适当优化的μ值时，我们发现LC技术提供了电荷转移激发随分子大小变化的一致图像。相比之下，我们发现广泛使用的B3LYP杂化泛函严重高估了激发态偶极矩，低估了垂直激发能，特别是对于较大的染料分子。本研究结果强调了TDDFT中长程交换校正对于研究太阳能电池染料激发态性质的重要性。
