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The printing of an efficient thermistor temperature sensor by using self-doped conducting polymers has been achieved. The use of a water-soluble polymer as the active material allows printing and processing in green solvents. The sensor showed a good sensitivity to temperature variations, with a temperature coefficient of resistance of −1.3%. The sensor also exhibited a better stability and reversibility towards humidity compared to the state-of-the-art poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS).

The ink conductivity of V -shape antennas from printed electronics were studied with terahertz near-field microscopy.

Titanium dioxide (TiO2) is a remarkable metal-oxide semiconductor with unique optoelectronic properties ideal for photovoltaics and photocatalytic conversion. The principal crystalline phases for TiO2 are anatase, rutile, and brookite. The combination of both anatase and rutile crystalline structures can positively impact the optoelectronic properties of TiO2 films. With standard sol–gel processing, high-temperature conversion generally yields one dominant phase and limits the combined use of anatase and rutile TiO2 for optoelectronic devices. We report on a singular route to controllably engineer hybrid nanocrystalline films of TiO2 at room temperature to synergistically exploit both anatase and rutile TiO2 phases. Relying on sol–gel chemistry, this approach starts from an amorphous film and uses photoinduced activation using a low-power laser to achieve specific spatially controlled pattern consisting of different TiO2 crystalline phases within the same film. While achieving remarkable precision, reprod...

New routes in additive devices fabrication techniques and advances in printable materials are required to meet the ever increasing demands for low-cost and large-area flexible electronics. In particular, perovskite-based materials have gained an appeal due to their unique optoelectronics and ferroelectrics properties, which may replace p-n junction in semiconductor devices. Metal-organic methylammonium lead trihalide perovskite formulations have been extensively studied in the last few years as promising materials for use in printed electronics, which do not require high temperatures or vacuum environment, contrary to conventional semiconductor fabrication techniques. In this work, digital inkjet-printing in ambient atmosphere is proposed as a deposition pathway for the fabrication of perovskite active layers in photodetector and thin-film photovoltaic device architectures. The device architecture containing a printed perovskite active layer sandwiched between TiO2 and Spiro-OMeTAD as electron and hole transport layers, respectively, as well as layer-on-layer fabrication and responsivity spectra of the perovskite-based device are presented.

In recent years, additive manufacturing has been evolving towards flexible substrates for the fabrication of printable electronic devices and circuits. Generally polymer-based, these emerging substrates suffer from their heat sensitivity and low glass-transition temperatures. As such they require new highly-localized sintering processes to treat the electronic inks without damaging the polymer-based substrate. Laser-based sintering techniques have shown great promises to achieve high-quality sintering locally, while controlling the heat penetration to preserve the polymer substrates integrity. In this report, we explore new optimization pathways for dynamic laser-based sintering of conductive silver inks. Multiple passes of a pulsed laser are first performed while varying pulse train frequencies and pulse energies as an attempt to optimize the properties of the silver inks. Then, time-domain pulse shaping is performed to alter the properties of the conductive inks. Together, these pathways allow for the careful control of the time-domain laser energy distribution in order to achieve the best electronic performances while preserving the substrate’s integrity. Sheet resistance values as low as 0.024Ω/□ are achieved, which is comparable to conventional 1-hour oven annealing, with the processing time dramatically reduced to the milisecond range. These results are supported by finite element modeling of the laser-induced thermal dynamics.

Multilayered graphene (MLG) grown by chemical vapor deposition (CVD) was examined as a negative electrode for lithium-ion batteries. Experimental parameters such as deposition time and temperature were examined to produce carbon loadings between 0.06–0.17 mg cm −2 and film thicknesses in the 1 μm range. The MLG thin films obtained on nickel substrate were used without conductive additive and binding agent in electrochemical tests to produce a capacity of ∼250 mAh.g −1 at the 5C rate. Films were further characterized by scanning electron microscopy, atomic force microscopy, grazing angle X-ray diffraction, X-ray photoelectron spectroscopy and Raman micro-spectroscopy mapping. By correlating the structural analysis to the electrochemical properties the importance of edge plane accessibility is emphasized. Separately, a pre and a post deposition treatment were used to improve the electrochemical performances, validating the structural performance limitation hypothesis. In particular, the use of argon plasma post treatment yielded major improvement of the electrochemical performance, which was ascribed to enhanced crystallite edge accessibility.

Lyra2REv2 is a hashing algorithm that consists of a chain of individual hashing algorithms, and it is used as a proof-of-work function in several cryptocurrencies. The most crucial and exotic hashing algorithm in the Lyra2REv2 chain is a specific instance of the general Lyra2 algorithm. This work presents the first hardware implementation of the specific instance of Lyra2 that is used in Lyra2REv2. Several properties of the aforementioned algorithm are exploited in order to optimize the design. In addition, an FPGA-based hardware implementation of a standalone miner for Lyra2REv2 on a Xilinx Multi-Processor System on Chip is presented. The proposed Lyra2REv2 miner is shown to be significantly more energy efficient than both a GPU and a commercially available FPGA-based miner. Finally, we also explain how the simplified Lyra2 and Lyra2REv2 architectures can be modified with minimal effort to also support the recent Lyra2REv3 chained hashing algorithm., 13 pages, accepted for publication in IEEE Trans. Circuits Syst. I. arXiv admin note: substantial text overlap with arXiv:1807.05764

Active inkjet materials are invoked in the fabrication of optoelectronic devices. These types of multilayer assemblies contain a variety of commercially available ink formulations. It is envisioned that a dielectric SU-8 material can be used in a FET-like structure to form an interlayer between conductive silver and semi-conductive MWCNT-doped PEDOT:PSS ink layers. These printed structures may be fabricated onto a polyimide based flexible substrate, for instance. These structures are a starting point for offering valuable information on layer-on-layer printing interactions and interface problematics within a complete inkjet device fabrication.

In recent years, metal-organic methylammonium lead trihalide perovskite formulations have been extensively studied and employed as active materials in a range of photovoltaic and photodetector devices. Perovskite-based materials have gain popularity due to their unique optoelectronic properties which allow for simple device architecture to reach high energy harvesting efficiencies and responsivities over the whole visible light spectrum. These materials offer an advantage over conventional semiconductor materials and fabrication techniques as they do not require high temperatures or vacuum environments which are beneficial for fabricating devices on flexible, heat sensitive substrates.As the demand for low-cost and large-area flexible electronics increases, in part due to the rise of the internet of things (IoT), new routes in additive device fabrication techniques and advances inprintable materials are required. In this work, digital inkjet-printing in ambient atmosphere is proposed as a fabrication pathway for perovskite based flexible photodetectors in thin-film device architectures. The devices consisting of a printed methylammonium lead trihalide perovskite layer and a printed Spiro-OMeTAD hole transport layer fabricated on indium tin oxide (ITO) coated Polyethylene terephthalate (PET) flexible substrates are shown to have an average responsivity at 0 V bias of 7.7 μA/Win the range of 400 nm to 850 nm which is increased to 0.53 mA/Wand 1.17 mA/W when biases of 0.5 V and 1.0 V are applied, respectively.

We demonstrate the terahertz (THz) transmission properties of printed electronic devices. An ultrathin vortex phase plate (VPP) has been fabricated by inkjet printing technology and our experimental results confirmed its expected resonance at 220 GHz. We show that printable electronics are a promising technique for fabricating ultrathin VPP in the THz frequency range.

This work describes a method for electrostatic deposition of graphene over a large area using controlled electrostatic exfoliation from a Highly Ordered Pyrolytic Graphite (HOPG) block. Deposition over 130 × 130 µm2 with 96% coverage is achieved, which contrasts with sporadic micro-scale depositions of graphene with little control from previous works on electrostatic deposition. The deposition results are studied by Raman micro-spectroscopy and hyperspectral analysis using large fields of view to allow for the characterization of the whole deposition area. Results confirm that laser pre-patterning of the HOPG block prior to cleaving generates anchor points favoring a more homogeneous and defect-free HOPG surface, yielding larger and more uniform graphene depositions. We also demonstrate that a second patterning of the HOPG block just before exfoliation can yield features with precisely controlled geometries.

We demonstrate a fast and large area-scalable methodology for the fabrication of efficient dye sensitized solar cells (DSSCs) by simple addition of graphene micro-platelets to TiO2 nanoparticulate paste (graphene concentration in the range of 0 to 1.5 wt%). Two dimensional (2D) Raman spectroscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM) confirm the presence of graphene after 500°C annealing for 30 minutes. Graphene addition increases the photocurrent density from 12.4 mA cm-2 in bare TiO2 to 17.1 mA cm-2 in an optimized photoanode (0.01 wt% graphene, much lower than those reported in previous studies), boosting the photoconversion efficiency (PCE) from 6.3 up to 8.8%. The investigation of the 2D graphene distribution showed that an optimized concentration is far below the percolation threshold, indicating that the increased PCE does not rely on the formation of an interconnected network, as inferred by prior investigations, but rather, on increased charge injection from TiO2 to the front electrode. These results give insights into the role of graphene in improving the functional properties of DSSCs and identifying a straightforward methodology for the synthesis of new photoanodes.

Graphene inks are becoming widely popular. However the vast majority of these inks are formulated in polar solvents with high-boiling points. Their slow evaporation is a bottleneck factor in roll-to-roll printing processes. Here, we developed a highly-conductive fast-drying graphene ink in isooctane, a non-polar and low-boiling solvent. For this purpose, a diblock copolymer containing pendant cholesterol groups was used during the exfoliation of natural graphite in isooctane. The polymer develops non-covalent supramolecular interactions with the graphene conjugated system, resulting in the formation of stable graphene dispersions (up to c = 4 mg mL−1). These dispersions were used for direct writing on a variety of substrates, and were shown to dry instantly after application. The influence of polymer concentration on graphene characteristics, on colloidal stability and on electrochemical characteristics has been studied. The lowest sheet resistance (80 Ω □−1) was obtained when 23% of the graphene surface was covered by the polymer. In this case, the flakes were constituted of 2–5 graphene layers. More extensive exfoliation, down to single-layer graphene, was achieved at greater surface coverage, but led to inks with higher sheet resistance. Thus, by combining a tailored polymeric dispersant, a smooth exfoliation process and a low-boiling non-polar ink solvent, we were able to prepare highly-conductive fast-drying graphene inks which should have a high potentital for the development of roll-to-roll printed electronics.

The nanoscale engineering of silicon can significantly change its bulk optoelectronic properties to make it more favorable for device integration. Phonon process engineering is one way to enhance inter-band transitions in silicon's indirect band structure alignment. This paper demonstrates phonon localization at the tip of silicon nanowires fabricated by galvanic displacement using wet electroless chemical etching of a bulk silicon wafer. High-resolution Raman micro-spectroscopy reveals that such arrayed structures of silicon nanowires display phonon localization behaviors, which could help their integration into the future generations of nano-engineered silicon nanowire-based devices such as photodetectors and solar cells.

Lyra2REv2 is a hashing algorithm that consists of a chain of individual hashing algorithms and it is used as a proof-of-work function in several cryptocurrencies that aim to be ASIC-resistant. The most crucial hashing algorithm in the Lyra2REv2 chain is a specific instance of the general Lyra2 algorithm. In this work we present the first FPGA implementation of the aforementioned instance of Lyra2 and we explain how several properties of the algorithm can be exploited in order to optimize the design., 5 pages, to be presented at the IEEE International Symposium on Circuits and Systems (ISCAS) 2019