Amidoamine dendron-based co-adsorbents: improved performance in dye-sensitized solar cells

Abstract

Three dendritic molecules EG0, EG1 and EG2 were synthesized and separately used as co-adsorbents in dye-sensitized solar cells (DSSCs) to explore their effect on controlling interfacial charge recombination. It was found that the resulting device with EG2 as the co-adsorbent (device EG2) displayed superior open-circuit voltage (V_OC), improved short-circuit current density (J_SC) and a higher power conversion efficiency (PCE) of 7.50%, as compared to the control device (N719) and the devices with EG0 or EG1 as the co-adsorbent (devices EG0 and EG1). Such improved performance is ascribed to the increase of the interfacial distance upon the introduction of EG2, and the formation of a more compact monolayer of the dye N719 and co-adsorbent EG2 at the interface, which shields the acceptors in the electrolyte from contacting the TiO₂ surface, hence reducing the back current and increasing the V_OC. On the other hand, the aggregation of dye molecules is restrained due to the competitive adsorption between dye N719 and co-adsorbent EG2, thus leading to the minimization of energy loss and the enhancement of J_SC. As a co-adsorbent, EG2 was also introduced to DSSCs using either the iodide electrolyte without the additive 4-tert-butylpyridine (TBP) or the cobalt electrolyte. The results showed that EG2 also displayed effective capability of suppressing interfacial charge recombination and reducing intermolecular energy transfer.