Direct PECVD growth of vertically erected graphene walls on dielectric substrates as excellent multifunctional electrodes

Abstract

A novel uniform multi-level matrix of vertically erected graphene walls is directly grown on a dielectric substrate by plasma enhanced chemical vapor deposition (PECVD) at 900 °C without the presence of any catalyst and post-transfer treatment. Such a two-level structure is composed of continuous vertically erected graphene sheets (the second level) on a nanocrystalline graphene film (the first level). A nanocrystalline film is formed in the first stage (<15 min), and the graphene walls initialize on the boundary C sp³ atoms as nucleation centers to grow the erected graphene walls as the second-level component. The microstructure of the graphene walls can be modified by plasma power, growth time and seed layer coating. The unique three-dimensional graphene structure possessed high hydrophobicity (contact angle: 141°), outstanding electron conductivity (sheet resistance: 198 Ω sq⁻¹), and tunable transparency (91.9–38.0% at 550 nm). The three-dimensional structure enables the graphene to act as an excellent electron transport network with high surface area in many aspects. The highly conductive graphene walls were used as the counter electrode of dye-sensitized solar cells (DSSC) with a photovoltaic efficiency of 6.01%, comparable to FTO-based DSSCs (6.10%). This in situ one-step growth indicates the great potential to fabricate excellent electrodes for photovoltaic and electronic applications.