共敏化有机染料分子电子结构和光学性能的理论研究

A theoretical investigation on the performance of co-sensitized organic dyes

本文利用密度泛函(DFT)和含时密度泛函理论(TD-DFT),研究了单一染料(C239、C259和修饰的C259(C259-N))以及共敏化染料(C239+C259和C239+C259-N)的电子结构和光学性能.结果表明,单一和共敏化条件下,新设计的含二噻吩并吡咯单元(DTP)的C259-N表现出与含环戊二噻吩单元(CPDT)的C259相近的光学性质.与单一染料相比,共敏化染料的光捕获率曲线未出现低谷,且在最大吸收处,其摩尔吸光率也有所提高.对共敏化染料/TiO_2复合物的研究表明,由3个O-Ti键和1个氢键形成的A共敏化模式下的共敏化体系稳定性较高,其中,含苯甲酸染料的垂直吸附一方面有利于染料/TiO_2界面的电子注入,另一方面可有效减轻界面的电荷复合.本文结果可为设计更加高效的有机共敏化剂提供理论依据.

By using density functional theory（DFT） and time-dependent DFT（TD-DFT） methods,the electronic structures and optical properties of a single dye（C239,C259 and C259-N） and co-sensitized dyes（C239＋C259 and C239＋C259-N） were studied.It is found that the effect of the replacement of dithienopyrrole（DTP） with cyclopentadithiophene（CPDT） in C259 on dye performance is negligible.There is no valley in the light-harvesting efficiency curve for the co-sensitized dyes,and the molar absorbtivity of the co-sensitized dyes at the maximum absorption has been improved compared with a single dye.Further investigations on the co-sensitized dye/TiO_2complexes show that the A co-sensitization mode with the formation of three O-Ti bonds and a new hydrogen bond is more stable.The co-sensitized dye with the benzoic acid group can stay perpendicular on the titanium surface,this is favourable for electron injection and can weaker electron-hole recombination at dye/TiO_2 interface.Our results can supply a guideline for experimental design of more efficient co-sensitized organic dyes for dye-sensitized solar cells（DSSCs）.