Alexander Bessonov

Layered memristive and memcapacitive switches for printable electronics

Novel computing technologies that imitate the principles of biological neural systems may offer low power consumption along with distinct cognitive and learning advantages. The development of reliable memristive devices capable of storing multiple states of information has opened up new applications such as neuromorphic circuits and adaptive systems. At the same time, the explosive growth of the printed electronics industry has expedited the search for advanced memory materials suitable for manufacturing flexible devices. Here, we demonstrate that solution-processed MoOx/MoS2 and WOx/WS2 heterostructures sandwiched between two printedxa0silver electrodes exhibit an unprecedentedly large and tunable electrical resistance range from 10(2) to 10(8)u2009Ω combined with low programming voltages of 0.1-0.2 V. The bipolar resistive switching, with a concurrent capacitive contribution, is governed by an ultrathin (<3 nm) oxide layer. With strong nonlinearity in switching dynamics, different mechanisms of synaptic plasticity are implemented by applying a sequence of electricalxa0pulses.

Polymer Surface Engineering for Efficient Printing of Highly Conductive Metal Nanoparticle Inks

An approach to polymer surface modification using self-assembled layers (SALs) of functional alkoxysilanes has been developed in order to improve the printability of silver nanoparticle inks and enhance adhesion between the metal conducting layer and the flexible polymer substrate. The SALs have been fully characterized by AFM, XPS, and WCA, and the resulting printability, adhesion, and electrical conductivity of the screen-printed metal contacts have been estimated by cross-cut tape test and 4-point probe measurements. It was shown that (3-mercaptopropyl)trimethoxysilane SALs enable significant adhesion improvements for both aqueous- and organic-based silver inks, approaching nearly 100% for PEN and PDMS substrates while exhibiting relatively low sheet resistance up to 0.1 Ω/sq. It was demonstrated that SALs containing functional -SH or -NH2 end groups offer the opportunity to increase the affinity of the polymer substrates to silver inks and thus to achieve efficient patterning of highly conductive structures on flexible and stretchable substrates.

Compound Quantum Dot–Perovskite Optical Absorbers on Graphene Enhancing Short-Wave Infrared Photodetection

Colloidal quantum dots (QDs) combined with a graphene charge transducer promise to provide a photoconducting platform with high quantum efficiency and large intrinsic gain, yet compatible with cost-efficient polymer substrates. The response time in these devices is limited, however, and fast switching is only possible by sacrificing the high sensitivity. Furthermore, tuning the QD size toward infrared absorption using conventional organic capping ligands progressively reduces the device performance characteristics. Here we demonstrate methods to couple large QDs (>6 nm in diameter) with organometal halide perovskites, enabling hybrid graphene phototransistor arrays on plastic foils that simultaneously exhibit a specific detectivity of 5 × 1012 Jones and high video-frame-rate performance. PbI2 and CH3NH3I co-mediated ligand exchange in PbS QDs improves surface passivation and facilitates electronic transport, yielding faster charge recovery, whereas PbS QDs embedded into a CH3NH3PbI3 matrix produce spatially separated photocarriers leading to large gain.

Flexible and Printable Sensors

Technical systems have become more and more complicated in recent decades and require more detailed control of their operation. This primarily relates to the safety, reliability, and efficiency of devices used in medicine, electronics, and other fields. Furthermore, with the development of the conception of the Internet of Things, a lot of attention has been paid to the interaction between humans and high-tech equipment and personal devices. Highly detailed information on the operation of a device or complex system can only be given by a large number of small sensors of different types. As we know, the most sophisticated sensory machine is a living organism. Formerly this thought led to the idea of creating a multisensory platform which would mimic the human skin capabilities. Electronic skin can simultaneously monitor many parameters such as temperature, strain, pressure, magnetic field, and intensity of light; it is also possible to emulate tactile and chemical perception. Nanotechnology serves as a tool for the creation of new sensor materials, and the development of printing technologies supports engineering low-cost, thin, lightweight, transparent, easily deformable, and biocompatible (even transient) electronic devices for monitoring external factors and processing information. In this review we discuss the state-of-the-art and prospects of new materials and technologies towards emerging flexible sensors.

Direct-write printing of reactive oligomeric alkoxysilanes as an affordable and highly efficient route for promoting local adhesion of silver inks on polymer substrates

A novel approach for improving the printability and adhesion of silver inks on flexible and stretchable polymeric substrates is reported. The method is based on polymer surface functionalisation with an organosilicon interlayer by solution processing and, more specifically, the deposition of a self-assembled layer (SAL) from thiol-containing oligomeric alkoxysilanes prepared under active medium conditions. We demonstrate the potential of SAL formation on polymer substrates by large-area uniform coating or by small feature printing. The direct-writing method, which is also referred to as reactive inkjet printing, enables the selective modification of polymer surfaces with functional thiol-containing interlayers, resulting in local adhesion enhancement of screen-printed silver nanoparticle inks. This study establishes that SALs printed from oligo(3-mercaptopropyl)(methoxy)siloxane (OMPMS) lead to significant adhesion improvements of both aqueous- and organic-based silver inks approaching approximately 100% for polyethylene naphthalate (PEN) and even polydimethylsiloxane (PDMS) substrates. Exceptional electrical and mechanical stabilities of the printed silver conductors under bending and stretching are demonstrated.

Molecular silicasol-based barrier coatings for organic electronics

A solution-processable approach to designing molecular silicasol-based barrier coatings for organic electronics has been developed. The barriers are assessed by the optical calcium test and demonstrate water-vapor permeation rates of about 10–2 g m–2 day–1. Silicasols are shown to be promising for the encapsulation of organic electronics devices, for which the resulting water-vapor permeation rates are sufficient (e.g., for organic field-effect transistors).