A novel σ-linkage to dianchor dyes for efficient dyes sensitized solar cells: 3-methyl-1,1-cyclohexane

We have synthesized two sensitizers based on the 3-methyl-1,1-cyclohexane, a novel σ-linkage to prepare dianchored dyes. These novel dyes are difunctionalized systems with aniline-donor (D), a π-conjugated spacer (π) based on thiophene or bithiophene and cyanoacetic acid as acceptor and anchoring group (A). The UV–vis absorption and the Differential Pulse Voltammetry have been used to study the effect of both σ-linkage and π-spacer. The relevant increase of the molar extinction coefficient of these dianchored dyes has been investigated by theoretical calculations. The dye bearing bithiophene results in a both broader and higher absorption as well as an adequate efficiency to transfer charge from D to A with respect to bithiophene dyes. The photovoltaic properties of these sensitizers without co-adsorbent have been studied. The novel difunctionalized derivatives present a relevant increase of the photocurrent density which results in a better performance with respect to the single dyes. The difunctionalized derivative based on bithiophene has given rise to an efficiency value of 7.8% and is stable up to 1000 h after the device assembly.