A promising anchor group for efficient organic dye sensitized solar cells with iodine-free redox shuttles: a theoretical evaluation

Abstract

The advantages and disadvantages of a new anchor group 2-(1,1-dicyanomethylene)rhodamine (DCRD) in D–π–A dyes for dye sensitized solar cells, compared with the commonly used anchor group cyanoacrylic acid (CA), were firstly investigated through DFT/TDDFT calculations on the dye/(TiO₂)₄₈/electrolyte interfacial electronic dynamics. It was found that the dissociative bidentate bridging mode is the most stable adsorption configuration on the TiO₂ anatase (101) surface for DCRD. The calculated results indicate that in contrast to dyes with a CA group, the DCRD anchor group-based dye has a red-shifted absorption spectrum, which is beneficial for the enhancement of J_sc. However, the S atom in the DCRD group near the semiconductor surface has strong interactions with I₂, which could lead to a higher I₂ concentration in the vicinity of the dye-coated TiO₂ surface, accelerating interfacial charge recombination. To avoid such shortcomings, a further optimization strategy for DCRD-based dyes was also proposed from a theoretical point of view. More importantly, we anticipate that dyes with the DCRD anchor group could show better performance in iodine-free redox shuttles-based DSSCs, in which the dye–I₂ interaction could be avoided.