Tunable hierarchical hexagonal nickel telluride (Ni₃Te₂) laminated microsheets as flexible counter electrodes for high-performance fibrous dye-sensitized solar cells: Accelerated electrocatalysis reduction of I₃⁻ ions

To develop highly active catalysts as counter electrodes is another promising way for improving the photovoltaic conversion efficiency (PCE) of fibrous dye-sensitized solar cells (FDSSCs). Then considering their applications in wearable electronic system, the designed fibrous counter electrodes (FCEs) should possess a good mechanical flexibility except high catalysis performances. Here in this work, hexagonal nickel telluride (Ni₃Te₂) microsheets with tunable diameters and thicknesses were in-situ prepared via an atmospheric pressure chemical vapor deposition method on nickel wires. Benefiting from their two-dimensional laminated structure and asymmetric crystalline structure, the Ni₃Te₂ microsheets show a high catalytic activity for the reduction of I₃^- → I^- during the photoelectrochemical processes in FDSSCs. And cell tests show that the maximum PCE of FDSSCs with Ni₃Te₂ FCEs reaches 11.81% (with an average value of 10.47%), which is 2.10 times that of the ones with Pt FCEs (5.62%). Furthermore, series of optimization on the microscale morphologies of Ni₃Te₂ microsheets indicates that the suitable diameter (30 ∼ 40 μm) and thickness (ca. 3.0 μm) are suitable for the diffusion and reduction of I₃^- ions. Besides, the FDDSCs with Ni₃Te₂ PCEs show a high cycling stability and an excellent dynamic bending stability (attenuation rate of 0.12‰ per bending cycle). This research would provide some insights into the design of high-performance FCEs for FDSSCs towards wearable electronic devices.