Search

A huge challenge is to control the nucleation of crystallites/aggregates in the solution during polymer film formation to generate desired structures. In this work, we investigate crystallization of P(NDI2OD-T2), a donor–acceptor polymer semiconductor, with controlled solution flow along the contact line between the drying film and solution through a seesaw-like pivoting of samples during polymer drying. By controlling the pivoting frequency/amplitude, various types of line patterns can be observed: (I) an array of fishbone-like stripes oriented in the film-growth direction; (II) the pinning–depinning of contact line (PDCL)-mechanism-defined patterned wires along the contact line; and (III) periodic twined crystalline line pattern oriented in the direction of the contact line. The rich variety of pattern formation observed is attributed to the distinctiveness of the donor–acceptor conjugated polymer structure. The result measured from thin-film transistors made of the generated films/structures showed that the charge mobility of P(NDI2OD-T2) does not change much with the film morphology, which supports recent controversy over the charge-transportation mechanism of some donor–acceptor polymer semiconductors.

Heterojunction based on two-dimensional (2D) layered materials is an emerging topic in the field of nanoelectronics and optoelectronics. Here, molybdenum sulfide (MoS2)-based Schottky diodes were fabricated using the field-effect transistor configuration with asymmetric metal contact structure. Gold and chromium electrodes were employed as drain and source electrodes to form Ohmic and Schottky contact with MoS2, respectively. The devices exhibited electrical rectifying characteristic with the current rectifying ratio exceeding 103and an ideal factor of 1.5. A physics model of the band diagram was proposed to analyze the gate-tunable rectifying behavior of the device. The dynamic rectification based on the diode circuit was further realized with the operating frequency up to 100 Hz. The devices were also demonstrated to show different sensitivities to the light under external biases in the opposite directions, with the highest photoresponsivity reaching 1.1 × 104A/W and specific detectivity up to 8.3 × 1012Jones at a forward drain bias of 10 V. This kind of 2D material-based Schottky diodes have the advantage of simplicity in design and fabrication, as well as superior electrical rectifying and photosensing characteristics, which have great potential for future integrated electronic and optoelectronic applications.

Polymer acceptors based on the polymerization of small-molecule acceptor (PSMAs) have developed rapidly in recent years. All-polymer solar cells (all-PSCs) composed of PSMAs and polymer donors not only retain the excellent mechanical properties, but also have better morphological properties than traditional polymer acceptors such as N2200. However, since PSMAs are generally not highly polymerized, their electron mobilities are generally lower than the hole mobilities of the high-molecular-weight polymer donors they are used with. In this work, we apply the sequential processing (SqP) method and use toluene as the processing solvent to prepare PSMA-based all-PSCs, which effectively improves the electron mobility and shows much higher efficiency (15.8 %) than the SqP device prepared from chloroform (13.9 %) – the conventional solvent used for high-performance PSMAs. Not only that, the efficiency of the toluene-processed SqP device is also higher than that of the device prepared by the traditional blending-casting (BC) method (14.2 %). In addition, for the first time, we reveal the film formation process of all-polymer active layers prepared by the SqP method using the in situ UV-Vis absorption technique, and investigate the vertical phase separation and the rate of exciton generation across the device using film-depth-dependent absorption spectroscopy, which systematically explained the effect of increased mobility on device parameters. This methodology is applied in two different all-polymer systems, namely, PM6:PYF-T-oand PM6:PY-IT, and both systems manifest the same conclusion.

We report the first demonstration of current-induced magnetization switching in a perpendicularly magnetized A1 CoPt single layer. We show that good perpendicular magnetic anisotropy can be obtained over a wide composition range of A1 Co1?xPtxsingle layers, which allows the fabrication of a perpendicularly magnetized CoPt single layer with a composition gradient that breaks the inversion symmetry of the structure. By fabricating a CoPt single layer with a gradient, we were able to evaluate spin-orbit torque (SOT) efficiency and successfully realize SOT-induced magnetization switching. Our study provides an approach for realizing current-induced magnetization in ferromagnetic single layers without attaching SOT source materials.