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Screen-printing inks containing various morphologies of carbon are used in the production of a variety of printed electronics applications. Particle morphology influences the rheology of the ink which will affect the deposition and therefore the electrical performance of a printed component. To assess the effect of both carbon morphology and concentration on print topography and conductivity, screen printable carbon inks with differing loading concentrations of graphite, carbon black and graphite nanoplatelets (GNPs) were formulated, printed and characterised, with rheological and novel print visualisation techniques used to elucidate the mechanisms responsible. Carbon morphology had significant effects on the packing of particles. The smaller carbon black particles had more interparticle interactions leading to better conductivities, but also higher ink viscosities and elasticities than the other morphologies. Increases in carbon concentration led to increases in film thickness and roughness for all morphologies. However, beyond a critical point further increases in carbon concentration led to agglomerations of particles, mesh marking and increases in surface roughness, preventing further improvements in the print conductivity. The optimal loading concentrations were identifiable using a custom-made screen-printing apparatus used with high speed imaging for all morphologies. Notable increases in filamentation during ink separation were found to occur with further increases in carbon concentration beyond the optimum. As this point could not be identified using shear rheology alone, this method combined with shear rheology could be used to optimise the carbon concentration of screen-printing inks, preventing the use of excess material which has no benefit on print quality and conductivity.

Binders used in screen-printed carbon-based inks are typically non-conductive. Photonic annealing and subsequent compression rolling have therefore been employed to remove binder and consolidate the conductive particles. Using this method, screen-printable carbon inks containing graphite only, graphite nanoplatelets and a combination of graphite and carbon black were assessed. Photonic annealing leads to the degradation of the polymer binder separating the carbon morphologies, with subsequent compression rolling leading to significant reductions in print film thickness, roughness and improvements in particle orientation. Both processes lead to electrical performance enhancement for all printed inks assessed. The process was most effective for single graphitic morphologies with large gaps between conductors. These saw significant improvements, with reductions in electrical resistivity from 1.91 to 0.23 Ω cm for the graphite ink. The mixed carbon ink saw smaller but still significant improvements in print roughness and resistivity, from 0.037 to 0.019 Ω cm. Therefore, these postprocesses could widen the applications of common, low-cost carbon morphologies in screen printing inks.

Conductive inks based on graphite and carbon black are used in a host of applications including energy storage, energy harvesting, electrochemical sensors and printed heaters. This requires accurate control of electrical properties tailored to the application; ink formulation is a fundamental element of this. Data on how formulation relates to properties have tended to apply to only single types of conductor at any time, with data on mixed types of carbon only empirical thus far. Therefore, screen printable carbon inks with differing graphite, carbon black and vinyl polymer content were formulated and printed to establish the effect on rheology, deposition and conductivity. The study found that at a higher total carbon loading ink of 29.4% by mass, optimal conductivity (0.029 Ω cm) was achieved at a graphite to carbon black ratio of 2.6 to 1. For a lower total carbon loading (21.7 mass %), this ratio was reduced to 1.8 to 1. Formulation affected viscosity and hence ink transfer and also surface roughness due to retention of features from the screen printing mesh and the inherent roughness of the carbon components, as well as the ability of features to be reproduced consistently.

Production of silicon solar cells necessitates cleanrooms to prevent dust contamination, which can lead to defects and reduced performance. This poses challenges for scaling up manufacturing and improving accessibility for device manufacture in less developed economies as cleanrooms represent an expensive and energy intensive investment, and so it is key that the next generation of solar technology differentiates from this. Perovskite has the potential to be far more robust and resilient to defects caused by dust particles, which then impacts on the capital cost of the equipment required for manufacture. This study evaluates the effects of non-conductive dust on planar perovskite devices, testing two different device structures with efficiencies exceeding 16%, testing an active area of 0.09 cm 2 . The setup simulated dust settling during the manufacturing process, expecting compromised performance in contaminated devices. Results revealed that devices with dust performed similarly to clean ones, with only limited losses in some performance metrics. High tolerance to contamination suggests that perovskite technology may remain operational under less controlled environments. These findings point toward a more accessible fabrication route reducing dependence on expensive cleanroom conditions typically required for silicon-based technologies. Manufacturing perovskite solar cells in dust-free environments is expensive and not practical in some settings. Here, the effect of non-conductive dust settling on small-area devices during manufacture is assessed, finding only minor drop-off in some performance metrics

Screen-printable carbon-based inks are available in a range of carbon morphologies and concentrations, resulting in various rheological profiles. There are challenges in obtaining a good print when high loading and elasticity functional inks are used, with a trade-off often required between functionality and printability. There is a limited understanding of how ink rheology influences the ink deposition mechanism during screen-printing, which then affects the print topography and therefore electrical performance. High speed imaging was used with a screen-printing simulation apparatus to investigate the effect of viscosity of a graphite and carbon-black ink at various levels of solvent dilution on the deposition mechanisms occurring during screen-printing. With little dilution, the greater relative volume of carbon in the ink resulted in a greater tendency towards elastic behavior than at higher dilutions. During the screen-printing process this led to the ink splitting into filaments while remaining in contact with both the mesh and substrate simultaneously over a greater horizonal length. The location of separating filaments corresponded with localized film thickness increases in the print, which led to a higher surface roughness (Sz). This method could be used to make appropriate adjustments to ink rheology to overcome print defects related to poor ink separation.

Organically coated steels are widely used in applications in which they are subjected to the natural environment and therefore require excellent corrosion resistance. Organic clearcoats are typically employed as a barrier that improves the overall corrosion resistance; however, they are typically derived from fossil fuel-based feedstock. A more sustainable alternative could be possible using sol–gel coatings. The application of a simple tetraethoxysilane (TEOS)-based sol–gel was applied to polyurethane-coated steels using a spray coater. The concentration of TEOS was altered to produce coatings containing either 2.5% or 10%. The 10% TEOS resulted in dense, homogeneous coatings that offered a significant improvement in corrosion resistance compared to an uncoated substrate. Whereas the 2.5% TEOS coatings were inhomogeneous and porous, which indicated a limitation of concentration required to produce a uniform coating. The successful demonstration of using a simple TEOS-based coating to improve the corrosion resistance of organically coated steel highlights the potential for further investigation into the use of sol–gels for these applications.