Molecular engineering of bithiazole-based organic dyes with different electron-rich linkers toward highly efficient dye-sensitized solar cells

A series of bithiazole-based dye sensitizers have been designed by employing various electron-rich moieties as pi-spacer, which are based on the reported experimentally synthesized dye T-BT, to shed a light on the impact of both the nature and position of electron-rich moiety on the efficiency of dyes in DSSCs. To evaluate the efficiency of these dyes, various key parameters associated with overall conversion efficiency (eta), including electronic and optical properties of free dyes are calculated, based on the computational methods. Besides, the dye/TiO2 structures have been taken into account to investigate the interfacial features of the dye sensitizers adsorbed on TiO2 semiconductor and explore the plausible mechanism of the electron injection. The results show that, compared with the reference dye, T-BT, the newly designed dyes with electron-rich moiety close to the donor group show a better efficiency for using in the DSSCs. Our calculations show that this result is valid for other electron-withdrawing auxiliary acceptor in the range of moderate to strong. Also, we found that the incorporation of pyrrolo [3,2 -b] pyrrole (PP) unit in the pi-spacer would be more favorable to enhance the efficiency of DSSCs, compared to other electron-rich groups. This computational study is expected to be a helpful guidance for the rational modification of organic dyes in future. (C) 2017 Elsevier B.V. All rights reserved.