End Group Effect of Asymmetric Benzodithiophene-Based Donor with Liquid-Crystal State for Small-Molecule Binary Solar Cell

Liquid-crystal small molecule donor (LC-SMD) is a new type organic semiconductor, which is attractive not only for the easy synthesis and purification, well-defined chemical structures, etc., but also for the LC state that makes the crystallinity and aggregation state of molecules adjustable. Here, one new LC-SMD (a-BTR-H4) is synthesized with 1D alkoxyl and 2D thiophene-alkylthiol side-chained benzo[1,2-b:4,5-b′]dithiophene core, trithiophene π-bridge, and 3-(2-ethylhexyl) rhodanine end group. a-BTR-H4 shows low LC transition temperature, 117 °C, however, counterpart material (a-BTR-H5) with the same main structure but 3-ethyl rhodanine terminal group does not show LC properties. Although a-BTR-H4/H5 show similar Ultraviolet–visible absorption spectrum and energy levels, a-BTR-H4 affords relatively high photovoltaic performances due to favorable blend morphology produced by the consistent annealing temperature of Y6-based accepters and liquid crystal temperature of donors. Preliminary results indicate that a-BTR-H4 gains a power conversion efficiency (PCE) of 11.36% for Y6-based devices, which is ascribed to better light harvest as well as balanced carrier generation and transport, while a-BTR-H5 obtains 7.57% PCE. Therefore, some materials with unique nematic LC phase have great application potential in organic electronics, and further work to utilize a-BTR-H4 for high-performance device is underway.     

Insulating Electrets Converted from Organic Semiconductor for High-Performance Transistors,Memories, and Artificial Synapses

Electrets are commonly used charged insulators that generate a quasi-permanent electric field. However, when conventional electrets come into direct contact with semiconductors, the energy level mismatch at the interface results in low memory speed and high energy consumption of electret devices due to both charge injection and storage being non-conducive. To address this, the n-type semiconductor N,N′-dioctyl-3,4,9,10-perylene tetracarboxylic diimide (C₈-PTCDI) is converted to C₈-PTCDI (D) via oxygen degradation. The resulting C₈-PTCDI (D) electrets, when charged using an electric field and/or light, retain the energy level of the n-type semiconductors to facilitate charge trapping. They also exhibit deeper trap energy levels and increased trap density, thereby enhancing the sheet charge density of C₈-PTCDI (D) electrets (7.47 × 10¹² cm⁻²). As a result, devices based on n-type electrets demonstrate lower operation voltage (2 V) of transistors, lower operation voltage (20 V) of memories, and lower energy consumption (3.5 fJ per spike) of artificial synapses compared to those without n-type electrets.     

Composition Waves in Solution-Processed Organic Films and Its Propagations from Kinetically Frozen Surface Mesophases

Organic thin films deposited from solution attract wide interest for next-generation (opto-)electronic and energy applications. During solvent evaporation, the phase evolution dynamics for different components at different locations are not synchronic within the incrementally concentrated liquid films, determining the final anisotropic morphology and performance. Herein, by examining tens of widely investigated optoelectronic organic films, the general existence of composition wave propagating along the surface-normal direction upon solidification is identified. The composition wave is initiated by a few nanometers thick surface mesophase kinetically forming at the foremost stage of phase transition, and afterward propagates toward the substrate during solvent evaporation. The composition waves exhibit well-defined wave properties, including spatial wavelength, period, amplitude, and propagation velocity. These wave properties are closely correlated with the evaporation rate and the diffusion rate of organic molecules, which determines the dynamically varied local composition gradient along the surface-normal direction. Such composition waves are commonly found for more than 80% of randomly examined solution-processed thin films for high-performance organic electronic devices including photovoltaic cells and field-effect transistors.     

Engineering Oncolytic Adenoviruses with VSVG-Decorated Tumor Cell Membranes for Synergistically Enhanced Antitumor Therapy

Oncolytic viruses hold great promise for cancer treatment but their practical applications are seriously impaired by a series of limitations. Herein, an engineered oncolytic adenovirus (OA) is constructed that can boost both the direct oncolysis and antitumor immune response of OA attributed to the increased tumor targeting and low-pH responsive fusogenic activity. The tumor cell membranes are decorated with vesicular stomatitis virus glycoprotein (VSVG) via vesicular stomatitis virus (VSV) infection and then used to mask OA (V-M@OA). After systemic administration, the engineered OA can target homologous tumors owing to the homing ability of tumor membranes. Then the unique low-pH responsive fusogenic activity of VSVG significantly enhances the replication of OA by promoting the whole virus infection process, resulting in remarkable virus-mediated tumoricidal effects and thus abundant in situ released tumor-associated antigens (TAAs). Meanwhile, VSVG on V-M@OA augments the adjuvanticity of OA and thus significantly enhancing the antitumor immune response. The synergism of virus-mediated killing and immune effects leads to significant tumor inhibition with no obvious side effects.     

High Performance and Multifunction Moisture-Driven Yin–Yang-Interface Actuators Derived from Polyacrylamide Hydrogel

High actuation performance of a moisture actuator highly depends on the presence of a large property difference between the two layers, which may cause interfacial delamination. Improving interfacial adhesion strength while increasing the difference between the layers is a challenge. In this study, a moisture-driven tri-layer actuator with a Yin–Yang-interface (YYI) design is investigated in which a moisture-responsive polyacrylamide (PAM) hydrogel layer (Yang) is combined with a moisture-inert polyethylene terephthalate (PET) layer (Yin) using an interfacial poly(2-ethylhexyl acrylate) (PEA) adhesion layer. Fast and large reversible bending, oscillation, and programmable morphing motions in response to moisture are realized. The response time, bending curvature, and response speed normalized by thickness are among the best compared with those of previously reported moisture-driven actuators. The excellent actuation performance of the actuator has potential multifunctional applications in moisture-controlled switches, mechanical grippers, and crawling and jumping motions. The Yin–Yang-interface design proposed in this work provides a new design strategy for high-performance intelligent materials and devices.