Increasing the open-circuit voltage and adsorption stability of squaraine dye binding onto the TiO2 anatase (101) surface via heterocyclic anchoring groups used for DSSC

We have predicted four squaraine (SQ) structures with different heterocyclic anchoring groups (HAGS), including hydantoin moiety (HY), rhodanine (RD), 2-(1,1-dicyanomethylene) (DCRD) and barbituric acid (BA), to simultaneously enhance the lower open-circuit photovoltage (V-oc) and adsorption stability of the gold-standard SQ dye with widely used carboxylic acid anchoring group (CA) without sacrificing its extremely large shortcircuit current (J(sc)). For the first time, these HAGS are put together to discuss their impacts on the relative adsorption stability and the intrinsic reasons affecting the V-oc, including adsorption modes, conduction band energy shift (Delta E-CB), electron injection, charge recombination, and the dye aggregation effects. Especially, charge decomposition analysis has been performed to explain the origin of different extent of Delta E-CB, and the reduced density gradient analysis offers a pictorial representation of the weak interactions between the two monomers. The results show that the adsorption stability order is BA approximate to HY > RD approximate to CA > DCRD. And the V-oc order is BA > HY > RD > CA > DCRD. In addition, we find these SQ dyes show comparable maximum photocurrent density (about 22 mA/cm(2)). Thus, SQ dyes with BA, HY, and RD are promising candidates for the experimental synthesis of high-performance dye sensitized solar cells.