A high-resolution large-area detector for quality assurance in radiotherapy.

Hadron therapy is an advanced radiation modality for treating cancer, which currently uses protons and carbon ions. Hadrons allow for a highly conformal dose distribution to the tumour, minimising the detrimental side-effects due to radiation received by healthy tissues. Treatment with hadrons requires sub-millimetre spatial resolution and high dosimetric accuracy.

Flexible large-area ultrasound arrays for medical applications made using embossed polymer structures.

With the huge progress in micro-electronics and artificial intelligence, the ultrasound probe has become the bottleneck in further adoption of ultrasound beyond the clinical setting (e.g. home and monitoring applications).

Vitality surveillance at distance using thin-film tandem-like narrowband near-infrared photodiodes with light-enhanced responsivity.

Remote measurement of vital sign parameters like heartbeat and respiration rate represents a compelling challenge in monitoring an individual's health in a noninvasive way. This could be achieved by large field-of-view, easy-to-integrate unobtrusive sensors, such as large-area thin-film photodiodes. At long distances, however, discriminating weak light signals from background disturbance demands superior near-infrared (NIR) sensitivity and optical noise tolerance.

Identification of the Origin of Ultralow Dark Currents in Organic Photodiodes.

Organic bulk heterojunction photodiodes (OPDs) attract attention for sensing and imaging. Their detectivity is typically limited by a substantial reverse bias dark current density (J ). Recently, using thermal admittance or spectral photocurrent measurements, J has been attributed to thermal charge generation mediated by mid-gap states.

Multidimensional Perovskites for High Detectivity Photodiodes.

Low-dimensional perovskites attract increasing interest due to tunable optoelectronic properties and high stability. Here, it is shown that perovskite thin films with a vertical gradient in dimensionality result in graded electronic bandgap structures that are ideal for photodiode applications. Positioning low-dimensional, vertically-oriented perovskite phases at the interface with the electron blocking layer increases the activation energy for thermal charge generation and thereby effectively lowers the dark current density to a record-low value of 5 × 10  mA cm without compromising responsivity, resulting in a noise-current-based specific detectivity exceeding 7 × 10 Jones at 600 nm.

Ultralow dark current in near-infrared perovskite photodiodes by reducing charge injection and interfacial charge generation.

Metal halide perovskite photodiodes (PPDs) offer high responsivity and broad spectral sensitivity, making them attractive for low-cost visible and near-infrared sensing. A significant challenge in achieving high detectivity in PPDs is lowering the dark current density (J) and noise current (i). This is commonly accomplished using charge-blocking layers to reduce charge injection.

Depolarization of multidomain ferroelectric materials.

Depolarization in ferroelectric materials has been studied since the 1970s, albeit quasi-statically. The dynamics are described by the empirical Merz law, which gives the polarization switching time as a function of electric field, normalized to the so-called activation field. The Merz law has been used for decades; its origin as domain-wall depinning has recently been corroborated by molecular dynamics simulations.

Near-Infrared Tandem Organic Photodiodes for Future Application in Artificial Retinal Implants.

Photovoltaic retinal prostheses show great potential to restore sight in patients suffering from degenerative eye diseases by electrical stimulation of the surviving neurons in the retinal network. Herein, organic photodiodes (OPDs) sensitive to near-infrared (NIR) light are evaluated as photovoltaic pixels for future application in retinal prostheses. Single-junction and tandem OPDs are compared.

Balancing Hole and Electron Conduction in Ambipolar Split-Gate Thin-Film Transistors.

Complementary organic electronics is a key enabling technology for the development of new applications including smart ubiquitous sensors, wearable electronics, and healthcare devices. High-performance, high-functionality and reliable complementary circuits require n- and p-type thin-film transistors with balanced characteristics. Recent advancements in ambipolar organic transistors in terms of semiconductor and device engineering demonstrate the great potential of this route but, unfortunately, the actual development of ambipolar organic complementary electronics is currently hampered by the uneven electron (n-type) and hole (p-type) conduction in ambipolar organic transistors.

Reconfigurable Complementary Logic Circuits with Ambipolar Organic Transistors.

Ambipolar organic electronics offer great potential for simple and low-cost fabrication of complementary logic circuits on large-area and mechanically flexible substrates. Ambipolar transistors are ideal candidates for the simple and low-cost development of complementary logic circuits since they can operate as n-type and p-type transistors. Nevertheless, the experimental demonstration of ambipolar organic complementary circuits is limited to inverters.

Pulse-modulated multilevel data storage in an organic ferroelectric resistive memory diode.

We demonstrate multilevel data storage in organic ferroelectric resistive memory diodes consisting of a phase-separated blend of P(VDF-TrFE) and a semiconducting polymer. The dynamic behaviour of the organic ferroelectric memory diode can be described in terms of the inhomogeneous field mechanism (IFM) model where the ferroelectric components are regarded as an assembly of randomly distributed regions with independent polarisation kinetics governed by a time-dependent local field. This allows us to write and non-destructively read stable multilevel polarisation states in the organic memory diode using controlled programming pulses.

Organic ferroelectric/semiconducting nanowire hybrid layer for memory storage.

Ferroelectric materials are important components of sensors, actuators and non-volatile memories. However, possible device configurations are limited due to the need to provide screening charges to ferroelectric interfaces to avoid depolarization. Here we show that, by alternating ferroelectric and semiconducting nanowires over an insulating substrate, the ferroelectric dipole moment can be stabilized by injected free charge carriers accumulating laterally in the neighboring semiconducting nanowires.

Mechanical and Electronic Properties of Thin-Film Transistors on Plastic, and Their Integration in Flexible Electronic Applications.

The increasing interest in flexible electronics and flexible displays raises questions regarding the inherent mechanical properties of the electronic materials used. Here, the mechanical behavior of thin-film transistors used in active-matrix displays is considered. The change of electrical performance of thin-film semiconductor materials under mechanical stress is studied, including amorphous oxide semiconductors.

Ambipolar Organic Tri-Gate Transistor for Low-Power Complementary Electronics.

Ambipolar transistors typically suffer from large off-current inherently due to ambipolar conduction. Using a tri-gate transistor it is shown that it is possible to electrostatically switch ambipolar polymer transistors from ambipolar to unipolar mode. In unipolar mode, symmetric characteristics with an on/off current ratio of larger than 10(5) are obtained.

A thin-film microprocessor with inkjet print-programmable memory.

The Internet of Things is driving extensive efforts to develop intelligent everyday objects. This requires seamless integration of relatively simple electronics, for example through 'stick-on' electronics labels. We believe the future evolution of this technology will be governed by Wright's Law, which was first proposed in 1936 and states that the cost of a product decreases with cumulative production.

Nanoscale design of multifunctional organic layers for low-power high-density memory devices.

We demonstrate the design of a multifunctional organic layer by the rational combination of nanosized regions of two functional polymers. Instead of relying on a spontaneous and random phase separation process or on the tedious synthesis of block copolymers, the method involves the nanomolding of a first component, followed by the filling of the resulting open spaces by a second component. We apply this methodology to fabricate organic nonvolatile memory diodes of high density.

Thin-film morphology of inkjet-printed single-droplet organic transistors using polarized Raman spectroscopy: effect of blending TIPS-pentacene with insulating polymer.

We report thin-film morphology studies of inkjet-printed single-droplet organic thin-film transistors (OTFTs) using angle-dependent polarized Raman spectroscopy. We show this to be an effective technique to determine the degree of molecular order as well as to spatially resolve the orientation of the conjugated backbones of the 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-Pentacene) molecules. The addition of an insulating polymer, polystyrene (PS), does not disrupt the π-π stacking of the TIPS-Pentacene molecules.

Controlled deposition of highly ordered soluble acene thin films: effect of morphology and crystal orientation on transistor performance.

Controlling the morphology of soluble small molecule organic semiconductors is crucial for the application of such materials in electronic devices. Using a simple dip-coating process we systematically vary the film drying speed to produce a range of morphologies, including oriented needle-like crystals. Structural characterization as well as electrical transistor measurements show that intermediate drying velocities produce the most uniformly aligned films.

The opto-electronic properties of isolated phenylenevinylene molecular wires.

The optoelectronic properties of dilute solutions of oligomeric and (broken-conjugation) polymeric phenylenevinylene chains were studied using the following techniques: optical absorption and (time-resolved) emission spectrophotometry, flash-photolysis time-resolved (real and imaginary) microwave conductivity, pulse-radiolysis time-resolved microwave conductivity, and pulse-radiolysis time-resolved optical absorption spectrophotometry. The following properties were determined: absorption and emission spectra, fluorescence quantum yields and decay times, exciton polarizabilities and dissociation probabilities, charge mobilities, and radical cation absorption spectra. The experimental results are compared with theoretical calculations of exciton polarizabilities, charge mobilities, and radical cation absorption spectra.

Flexible active-matrix displays and shift registers based on solution-processed organic transistors.

At present, flexible displays are an important focus of research. Further development of large, flexible displays requires a cost-effective manufacturing process for the active-matrix backplane, which contains one transistor per pixel. One way to further reduce costs is to integrate (part of) the display drive circuitry, such as row shift registers, directly on the display substrate.