Heteroleptic ruthenium antenna-dye for high-voltage dye-sensitized solar cells

Abstract

A new ruthenium photosensitizer, coded CYC-B7, incorporating a bithienyl-carbazole antenna ligand was designed and prepared for improving the open-circuit voltage (V_oc) of a dye-sensitized solar cell (DSC) device. This new sensitizer displays the low energy MLCT transition band centered at 551 nm with a high molar absorption coefficient of 2.19 × 10⁴ M⁻¹ cm⁻¹. In addition, a simple approach to reduce the aggregation of bulky ruthenium dyes assembled onto the surface of TiO₂ film is demonstrated. The cell based on this new heteroleptic ruthenium dye provides a high V_oc of 788 mV and an overall conversion efficiency (η) of 8.96%. The functionality of carbazole in CYC-B7 resulting in the increases of the V_oc value of the corresponding device is verified by comparing with the performance of the DSC sensitized with a structurally similar dye without carbazole.