a 贵州大学化学与化工学院 贵阳 550025;
b 厦门大学化学与化工学院固体表面物理化学国家重点实验室和福建省理论与计算化学重点实验室 厦门 361005
Unique Metal Di-Porphyrin Dyes with Excellent Photoelectronic Properties for Solar Cells：Insight from Density Functional Calculations
Zhu Chuna,b, Cao Zexingb
a School of Chemistry and Chemical Engineering, Guizhou University, Guizhou 550025, China;
b State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
A new type of metal di-porphyrin dyes have been designed and characterized by density functional calculations. Structural optimizations and subsequent frequency calculations for the isolated dyes were performed using the B3LYP hybrid functional in combination with the all-electron 6-31G(d) basis set. Bulk solvent effects were evaluated by using the continuum solvation model of SMD. Vertical excitation energies were computed by means of time-dependent density functional theory with CAM-B3LYP functional. The two-dimensional slab model of the most stable anatase TiO2 (101) surface was used to calculate the structural and electronic properties of dye-TiO2 system by using the plane-wave technique implemented in Vienna ab initio simulation package (VASP). The electron injection times from the dye to the semiconductor were estimated by using a model derived from the Newns-Anderson approach. Calculations show that these novel porphyrin-based sensitizers have a strong light harvesting ability and an excellent charge separation in the excited states. Their optical and charge-transfer properties can be well modulated by incorporating different metals and different conjugated macrocycles. Moreover, the more positive energy level of HOMO orbital of the metal di-porphyrin dye than the bottom of conduction band of TiO2 ensures an effective electron injection from the excited dyes to TiO2, and its energy level of LUMO orbital can nicely match various redox couples to facilitate regeneration of the oxidized dyes. Accordingly the porphyrin-based complexes are quite promising for fabrication of the high performance dye-sensitized solar cells. Based on the first-principles calculations, plausible mechanisms for direct and indirect electron injections from the adsorbed dye to TiO2 have been discussed. In the indirect process, the dye is initially promoted to the excited state with the charge separation under light excitation of relatively short wavelength region, followed by the electron transfer from the excited dye to TiO2. Such electron injection process is predicted to be very fast and the estimated electron injection times are only about 20 fs. The direct electron injection from dye to TiO2 may occur under optical excitation in relatively long wavelength region.
朱纯, 曹泽星. 高效金属双卟啉染料的计算设计及其敏化TiO2半导体复合体系的理论研究[J]. 化学学报, 2013, 71(11): 1527-1534.
Zhu Chun, Cao Zexing. Unique Metal Di-Porphyrin Dyes with Excellent Photoelectronic Properties for Solar Cells：Insight from Density Functional Calculations. Acta Chimica Sinica, 2013, 71(11): 1527-1534.