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Title: Nanomaterials-based inks for flexible electronics, energy and photocatalytic applications
Author: Tomarchio, Flavia
ISNI:       0000 0004 7229 8774
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2018
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Due to the combination of their electronic, optical and mechanical properties, graphene and other layered materials (GRMs) have great potential for applications such as flexible optoelectronics and energy storage. Given that GRMs can be dispersed in solvents, solution processing is a particularly interesting approach that allows large volume production with tailored properties according to the targeted applications. \par In this dissertation I investigate liquid phase exfoliation and formulation of GRMs-based inks for flexible (opto) electronics, energy and photocatalysis. First I develop a protocol for the characterization of graphene inks, based on the statistical analysis of their Raman spectra. Such a tool is essential because of the scattering of characteristics in liquid-phase exfoliated material. I then report two novel processing techniques. The first consists on the exfoliation of graphene in organic solvents by the means of $\alpha$-functionalized alkanes as stabilising agents, which allows yield by weight ($Y_W$) of $\sim 100\%$. The second is based on exfoliation of graphite by microfluidization, where the material is stabilised in aqueous solution, with concentrations up to 100g/L. Such inks are successfully deposited by blade coating, leading to films of conductivity $\sim$ 2$\cdot$10$^4$ S/m at 25$\mu$m. I then investigate the use of graphene inks in optoelectronics and energy applications: First, I investigate inkjet printed graphene as hole injection layer (HTL). The cells with graphene HTL show high long-term stability, retaining 85$\%$ of the initial fill factor after 900 hrs in damp heat conditions. I then demonstrate flexible displays with graphene-SWNTs as pixel electrode. A 4x4 inch$^2$ demonstrator is realised integrating the ink into 12,700 pixels. I investigate graphene/MoO$_3$ electrode for supercapacitors with a specific capacitance of 342 F/cm$^3$. The electrode shows high cyclic stability, preserving $\sim$96$\%$ of the initial capacitance after 10,000 cycles. I finally report the production of TiO$_2$/exfoliated graphite as efficient photocatalytic composite able to degrade $\sim$100$\%$ more model pollutant with respect to TiO$_2$.
Supervisor: Ferrari, Andrea Carlo Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
Keywords: graphene ; layered materials ; energy ; display ; photocatalysis