Observation of Coalescence Process of Silver Nanospheres During Shape Transformation to Nanoprisms

In this report, we observed the growth mechanism and the shape transformation from spherical nanoparticles (diameter ~6 nm) to triangular nanoprisms (bisector length ~100 nm). We used a simple direct chemical reduction method and provided evidences for the growth of silver nanoprisms via a coalescence process. Unlike previous reports, our method does not rely upon light, heat, or strong oxidant for the shape transformation. This transformation could be launched by fine-tuning the pH value of the silver colloidal solution. Based on our extensive examination using transmission electron microscopy, we propose a non-point initiated growth mechanism, which is a combination of coalescence and dissolution–recrystallization process during the growth of silver nanoprisms

Low temperature sintering of inkjet printed metal precursor inks for organic electronic applications

As a nascent technology that developed during the last decades from only printing text and graphics into an important scientific research tool for R&D, inkjet printers are nowadays used as a highly reproducible non-contact patterning tool. In contrast to non-digital patterning tools, inkjet printing represents an additive technique that requires only small amounts of functional materials and is therefore characterized as being a highly efficient materials patterning technique. In particular, inkjet printing of metal precursor materials has been used more and more during the last few years, in order to produce conductive features for plastic electronic applications. Here, we present our recent results in the sintering of inkjet printed metal nanoparticle dispersion on cost-effective polymer foils. In order to sinter the particles at speeds that are compatible with roll-to-roll speeds, we have used combinations of innovative sintering methods. Conductivity values between 40 and 60% were hereby obtained in a few seconds to minutes by using either photonic or plasma pre-sintering followed by microwave flash sintering. cop. 2013; Society for Imaging Science and Technology

Impact of Si DRIE on vibratory MEMS gyroscope performance

Today angular rate sensors (gyroscopes) for automotive application are fabricated by a silicon surface micromachining process (SMM). One critical performance parameter of these micromachined vibratory gyroscopes is the mechanical coupling between the drive and sense mode due to manufacturing imperfections. Excessive coupling, called quadrature error, leads to large zero rate output (ZRO or Q-Bias). This paper discusses for the first time, the dependence between quadrature error and profile asymmetries in relevant spring structures with respect to non-uniformities of the silicon deep reactive ion etch (Si DRiE) systems used for the SMM processing

Simulation and prediction of the thermal sintering behavior for a silver nanoparticle ink based on experimental input

In order to develop a prediction model for resistivity evolution during isothermal sintering, a commercial silver nanoparticle ink was characterized for its metal content, particle size and behavior upon heating. Electrical properties, mass loss behavior, grain size development and material densification were studied for thermal sintering at 175 degrees C. The correlation between mass loss, height loss of the resulting sintered structures, grain size and electrical resistivity was investigated to gain further understanding of the silver nanoparticle sintering process. The results of thermal sintering were used to calibrate a discrete element sintering model that provides microstructural properties with which the resistivity development at 150 and 200 degrees C was successfully predicted. The model was validated by experimental data obtained at these temperatures. A variation of particle size and particle size distribution in the simulations furthermore illustrate their influence on final resistivity showing that using small particles with a broad distribution are preferable for reducing the final resistivity of the inkjet-printed pattern

Thermal Stable High-Efficiency Copper Screen Printed Back Contact Solar Cells

The high usage of silver in industrial solar cells may limit the growth of the solar industry. One solution is to replace Ag with copper. A screen printable Cu paste is used herein to metallize industrial interdigitated back contact (IBC) solar cells. A novel metallization structure is proposed for making solar cells. Cu paste is applied to replace the majority of the Ag used in IBC cells as busbars and fingers. Cu paste is evaluated for use as fingers, and solar cells are made to test conversion efficiency and reliability. The Cu paste achieves comparably low resistivity, and Cu paste printed cells demonstrate similar efficiency to Ag paste printed cells, with an average efficiency of 23%, and only 4.5 mg W−1 of Ag usage. Also, the solar cells are stable and no Cu in-diffusion is observed under damp heat (85 °C, 85% relative humidity) and thermal stress (200 °C) for 1000 h, respectively. All processes used in this study can be carried out with industrial equipment. These findings reveal a new application for Cu pastes and point to a new direction for reducing Ag utilization and cost.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Photovoltaic Materials and DevicesElectrical Sustainable Energ

Merging of metal nanoparticles driven by selective wettability of silver nanostructures

The welding and sintering of nanomaterials is relevant, for example, to form electrical contacts between metallic particles in printed electronic devices. Usually the welding of nanoparticles is achieved at high temperatures. Here we find that merging of two different metals, silver and gold nanoparticles, occurs on contact at room temperature. The merging process was investigated by experimental and molecular dynamics simulations. We discovered that the merging of these particles is driven by selective wettability of silver nanoparticles, independent of their size and shape (spheres or rods); silver behaves as a soft matter, whereas gold as a hard surface being wetted and retaining its original morphology. During that process, the silver atoms move towards the surface of the Au nanoparticles and wrap the Au nanoparticles in a pulling up-like process, leading to the wetting of Au nanoparticles. © 2014 Macmillan Publishers Limited