ZnO/PbS core/shell nanorod arrays as efficient counter electrode for quantum dot-sensitized solar cells

Abstract

To improve the electrochemical catalytic activity of the counter electrode (CE) to polysulfide electrolyte that commonly applied in quantum dot-sensitized solar cells (QDSSC), combination of catalysts with nanostructured materials is equally important as it is in the case of photoanodes. Here, we design and fabricate a new catalytic electrodes by combining PbS nanoparticles catalyst with ZnO nanorods arrays (NRs) for use as CEs in QDSSC. The ZnO/PbS core/shell CEs are prepared via the combination of chemical bath deposition and successive ionic layer adsorption and reaction methods. Compared with planar CEs, the ZnO NRs framework presents larger surface area for loading more PbS catalysts and easy accessibility of electrolyte. Additionally, the ZnO NRs core offers an excellent electron pathway for shuttling electrons to highly catalytic PbS sites due to the high electrical conductivity of ZnO nanorods. Therefore, the ZnO/PbS composite CEs exhibit much higher catalytic activity for polysulfide electrolyte than conventional Pt CE. As a result, the power conversion efficiency of QDSSC with the optimized ZnO/PbS CEs increase by nearly 120% and 78% compared to that with planar Pt and bare PbS CE, respectively.