Modulation of Acceptor Position in Organic Sensitizers: the Optimization of Intramolecular and Interfacial Charge Transfer Process.

With respect to cyanoacryclic acid as traditional acceptor and anchoring group in dye-sensitized solar cells, the introduction of stronger electron-deficient groups has greatly expanded the scope of molecular design and increased their efficiencies for organic dyes. In this contribution, benzothiadiazole (BTD) was selected as a representative acceptor to illustrate the influence of its position on the photophysical properties and corresponding photovoltaic performances. Through the insertion of BTD in different positions of framework with same composition units and order, four sensitizers were designed and synthesized. The structure-property relationship demonstrated the preference of suitable position of electron acceptor for optimization of the spectra response and interfacial charge transfer. In our system, dye LI-96 with BTD in the middle of conjugated bridge showed the broadest spectrum and achieved the best photovoltaic performance (8.25%), which may pave a new way to design or optimize the efficient sensitizers by rational design of acceptor position.