Preparation of nickel selenide by pulsed-voltage electrodeposition and its application as a highly-efficient electrocatalyst at counter electrodes of quantum-dot sensitized solar cells

We fabricate the nickel selenide thin films on fluorine-doped tin oxide conducting glass subtract using pulsed-voltage electrodeposition method for counter electrodes in quantum-dot-sensitized solar cells. The novelty of this work is nickel selenides are prepared by PVE significantly differs from the traditional continuous-voltage electrodeposition in morphology, compositions, and electrocatalytic activities. In general, NiSe2-PVE films consist of clusters with crystalline NiSe2 nanoparticles which remain nanoporous because application of anodic bias during pulsed electrodeposition enables diffusion layer of H2SeO3 recover from the deposition. The subsequent short cathodic bias not only facilitates new nucleation of nickel selenide but also hinders grain growth. In contrast, Ni3Se2-CVE film consists dense larger Ni3Se2 grains with surface microcracks attributed to continuous grain growth and accumulated film stress. Hence, NiSe2-PVE enhances electrocatalytic activity in polysulfide electrolyte in an effective manner when compare to Ni3Se2-CVE, owing to significantly more electrocatalytic active sites and enhance charge and mass transports. As an outcome, QDSSC with NiSe2-PVE CE achieve significantly higher power conversion efficiency of 4.46% than those of cells with Pt (2.62%) and Ni3Se2-CVE (2.63%) CEs. Furthermore, electrochemical stability in polysulfide electrolyte medium is reasonably high.