A Strategy To Boost the Efficiency of Rhodanine Electron Acceptor for Organic Dye: From Nonconjugation to Conjugation.

Rhodanine-3-acetic acid is a very important and common electron acceptor of organic dye for dye-sensitized solar cells (DSSCs). However, the photovoltaic performances of organic dyes with rhodanine-3-acetic acid are relatively poor in the great majority of cases due to its nonconjugated structure between rhodanine ring and carboxyl anchoring group. Herein, a rhodanine derivative with conjugated structure between rhodanine ring and anchoring group is first employed as electron acceptor for TiO2-based DSSCs. Organic dye with this conjugated electron acceptor can not only maintain wide absorption spectrum but also greatly improve the electronic structure and adsorption geometry on TiO2, which significantly enhances the electron injection and slows the charge recombination. So the power conversion efficiency of DSSC based on organic dye CRD-I with this conjugated electron acceptor is increased by 2 times as compared with DSSC based on organic dye RD-I with nonconjugated rhodanine-3-acetic acid. Moreover, it is also found that CRD-I is superior to RD-I with respect to DSSC stability and binding ability to TiO2. This work unambiguously demonstrates that the conjugated rhodanine derivative is a highly promising electron acceptor and provides a new strategy for high-efficiency rhodanine-based organic dyes in DSSCs.