Highly Efficient and Durable Quantum Dot Sensitized ZnO Nanowire Solar Cell Using Noble-Metal-Free Counter Electrode

A highly efficient quantum dot sensitized solar cell has been fabricated using a CdSe/CdS cosensitized ZnO nanowire array as a photoelectrode (PE), ordered mesocellular carbon foam (MSU-F-C) as a counter electrode (CE), and a polysulfide electrolyte as a hole transporter. The nanowire structure provides efficient photoelectron collection and light harvesting, and CdSe/CdS cosensitization allows utilization of the whole visible wavelength region of the incident solar spectrum. The MSU-F-C used here provides an extremely high surface area and the ordered large size mesopores with an interconnected pore structure, which facilitate diffusion of redox relay in the electrolyte. As a result, it exhibits low charge transfer resistance ( R ct ) between the CE/electrolyte interface and thus presents highly efficient photovoltaic performance, compared to conventional noble-metal-based CEs. The cell with MSU-F-C CE yields the highest power conversion efficiency of 3.60%, with V oc, J sc, and FF of 685 mV, 12.6 mA/cm 2, and 0.42, respectively. Furthermore, it exhibits high durability in the polysulfide electrolyte with remarkable stability irrespective of the solvent used in the electrolyte solution.