Nazifah Islam

Electrocatalytic properties of a vertically oriented graphene film and its application as a catalytic counter electrode for dye-sensitized solar cells

Vertically oriented graphene (VOG), with graphene sheets perpendicular to the substrate, exhibits meritorious electrocatalytic properties due to the fully exposed graphene (or graphitic) edges and other plasma introduced defects, even without any heteroatom functionalization. We report the growth and electrocatalytic properties of VOG by plasma-enhanced chemical vapor deposition using methane and nitrogen as source gases. Nitrogen was adopted as plasma ancillary gas to obtain a higher plasma temperature that promotes VOG growth with better electrocatalytic performance, as comparative studies demonstrated. Electron transfer dynamics measurement using a Fe(CN)63−/4− redox couple found reduction and oxidation peak-to-peak separation as low as 70 mV, indicating rapid electron-transfer kinetics. The electrocatalytic activity of the VOG electrode on an I−/I3− redox couple was found approaching that of platinum. Using VOG as the counter electrode for dye-sensitized solar cells (DSSCs), a promising power conversion efficiency of 7.63% was demonstrated. Electrochemical impedance spectroscopic study further discloses the impact of VOG properties on DSSC performance.

Mesoporous scaffolds based on TiO2 nanorods and nanoparticles for efficient hybrid perovskite solar cells

In a mesoporous hybrid perovskite solar cell (PSC), the mesoporous scaffold plays key roles in controlling the crystallization of the perovskite material and in the charge carrier transport, and hence is critical for developing highly efficient PSCs. Here we report a study on blending micrometer-long TiO2 nanorods (NRs) into the commonly used nanoparticles (NPs) to optimize the mesoporous structure, with the aim of enhancing the perovskite material loading and connectivity as well as light harvesting. It was found that with 5–10% of NR incorporation, a uniform scaffold can be spin-coated and the PSC performance was improved. In comparison to the pure NP-based device, the power conversion efficiency was increased by about 27% when 10% of the NRs were incorporated, due to enhanced light harvesting and charge collection. However, with more NR blending, a homogeneous scaffold cannot be formed, resulting in PSC performance degradation. These findings contribute to a better design of mesoporous scaffolds for high-performance PSCs.