Adsorption orientation effects of porphyrin dyes on the performance of DSSC: Comparison of benzoic acid and tropolone anchoring groups binding onto the TiO2 anatase (101) surface

摘要

A new porphyrin dye with tropolone anchoring group showing superior stability but lower efficiency versus the promising dye YD2-o-C8 with benzoic acid anchoring group was theoretically investigated for the first time. A series of important parameters related to the efficiency of DSSC were calculated to explore the nature of the experimentally observed lower efficiency and superior stability of tropolone-based solar cells. We found these two dyes with different anchoring groups show comparable electron injection and dye regeneration process. Interestingly, the red-shifted absorption spectrum, relatively weaker ability of releasing protons, and the larger conduction band energy shift of tropolone-based dyes all demonstrated it should show better performance than the benzoic acid dyes, which contradicts with the experimental results. However, through investigating the interaction between the porphyrin dye and the semiconductor by analyzing the electron localization function of the porphyrin dye and preforming energy decomposition analysis, we found that the direction of lone-pair electrons of carbonyl oxygen in the tropolone-based dye makes the dye prefer to adsorb on the surface in an inclined way, in contrary to the benzoic acid-based dye that favored a vertical adsorption. The inclined adsorption could significantly accelerate the charge recombination process between the injected electrons and the oxidized dye, leading to a decreased efficiency of DSSC. (C) 2017 Elsevier B.V. All rights reserved.