半菁染料作为染料敏化太阳能电池吸光材料的理论研究

采用第一性原理研究了半菁-二氧化钛团簇形成的配合物(hemicyanine-(TiO₂)_n)的光电子转移过程, 这里n分别取5, 9, 15. 配合物基态构型采用密度泛函理论方法进行优化, 而激发态采用含时密度泛函理论进行计算. 采用长程相关校正的密度泛函CAM-B3LYP和ωB97X-D计算的激发能与实验值吻合得很好. 依据广义Mulliken-Hush (GMH)公式, 基于密度泛函理论得到的波函数被用来计算电荷转移积分, 进而可根据Marcus理论计算出电荷分离速率常数(k_CS)和电荷回传速率常数(k_CR). 计算结果表明电子从染料到(TiO₂)_n团簇的传递有多条通道, 这使得k_CS具有更大值, 相反, 只具有单通道的电荷回传降低了k_CR值, 与k_CS相比甚至可以忽略, 这表明在所研究的体系中电荷回传是不利的.

Theoretical Study of Hemicyanine Dye as a Dye-Sensitized Solar Cell Light-Absorbing Material

We used first-principles calculations to investigate the photo-induced electron transfer (PIET) process of the hemicyanine-(TiO₂)_n complex ((TiO₂)_n-dye) for n=5, 9, 15. The geometries of the (TiO₂)_n-dye in the ground state were optimized using density functional theory (DFT) and their excited states were investigated using the time-dependent DFT (TDDFT) method. The excited energies, which were calculated using the longrange- corrected functionals, CAM-B3LYP and ωB97X-D, were in good agreement with the experimentally observed values. The wave functions based on DFT were used to calculate the charge transfer integrals by the generalized Mulliken-Hush (GMH) approach. In addition, the photo-induced charge separation rate constant (k_CS) and charge recombination rate constant (k_CR) were calculated using Marcus theory. The calculated results showed that there were a cascade of electron transfer channels from the dye into the (TiO₂)_n cluster, which increases the k_CS value. In contrast, the single channel of charge recombination decreases the k_CR value, which is negligible compared with k_CS, indicating that electron recombination is not favored.