S-alkylbenzothiophenium-based solid-state electrolyte for efficient quantum-dot sensitized solar cells

Abstract

Developing cost-effective solid-state electrolyte is a urgent issue and a common request for (photo) electrochemical cells. In this work, a series of organic ionic conductors based on the S-substituted benzothiophenium salts have been synthesized via a simple and low-cost method. Research on the thermal behavior, optical absorption and ionic conductivity shows that S-methylbenzothiophenium tetrafluoroborate ([MBT]BF4) among them have the good thermal stability, high ionic conductivity and no absorption in the visible region. And the solid-state electrolyte using [MBT]BF4 as the matrix exhibits the good interfacial compatibility with photoanode. Applying this solid-state electrolyte into the quantum-dot sensitized solar cell (QDSSCs), the device achieves an open circuit voltage of 0.71 V, a short circuit current density of 20.73 mW cm−2, and a power conversion efficiency of 5.49% which is higher than those previously reported for the solid-state QDSSCs.