Simplified Y6-Based Nonfullerene Acceptors: In-Depth Study on Molecular Structure-Property Relation, Molecular Dynamics Simulation, and Charge Dynamics.

Two new Y6 derivatives of symmetrical YBO-2O and asymmetrical YBO-FO nonfullerene acceptors (NFAs) are prepared with a simplified synthetic procedure by incorporating octyl and fluorine substituents onto the terminal 2-(3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile (INCN) moiety. By moving the alkyl substituents on the Y6 core to the terminal INCN moiety, the lowest unoccupied molecular orbital of the YBO NFAs increases without decreasing solubility, resulting in high open-circuit voltages of the devices. Molecular dynamics simulation shows that YBO-2O/-FO preferentially form core-core and terminal-terminal dimeric interactions, demonstrating their tighter packing structure and higher electron mobility than Y6, which is consistent with 2D grazing incidence X-ray scattering and space charge limited current measurements. In blend films, the hole transfer (HT) from YBO-2O/-FO to the polymer donor PM6 is studied in detail by transient absorption spectroscopy, demonstrating efficient HT from YBO-FO to PM6 with their suitable energy level alignment. Despite the simplified synthesis, YBO-FO demonstrates photovoltaic performance similar to that of Y6, exhibiting a power conversion efficiency of 15.01%. Overall, this design strategy not only simplifies the synthetic procedures but also adjusts the electrical properties by modifying the intermolecular packing and energy level alignment, suggesting a novel simplified molecular design of Y6 derivatives.

Highly Stable Bulk Perovskite for Blue LEDs with Anion-Exchange Method.

To date, the light emitting diode (LED) based halide perovskite was rapidly developed due to the outstanding property of perovskite materials. However, the blue perovskite LEDs based on the bulk halide perovskites have been rarely researched and showed low efficiencies. The bulk blue perovskite LEDs suffered from insufficient coverage on the substrate due to the low solubility of the inorganic Cl sources or damaged by the structural instability with participation of organic cations. Here, we show the new method of fabricating stable inorganic bulk blue perovskite LEDs with the anion exchange approach to avoid use of insoluble Cl precursors. The devices showed nice operational spectral stability at the desired blue emission peak. The bulk perovskite blue LEDs showed a maximum luminance of 1468 and 494 cd m-2 for the 490 and 470 nm emission peaks, respectively.

Radio-frequency-transmitting hexagonal boron nitride-based anti- and de-icing heating system.

Anti- and de-icing heating systems are used to both prevent the accumulation of ice and to remove it and thus avoid damage. Typically, anti- and de-icing heating systems employ carbon-based materials, metal frames, and bulky ceramic structures. These structures generally lead to the loss of radio-frequency (RF) signals and are also relatively heavy. Therefore, RF equipment such as radar domes (radomes) and antennas require anti- and de-icing systems with high RF transmittance for normal operation. In this work, we fabricated a fluorine-doped tin oxide (FTO) wave pattern covered with hexagonal boron nitride (h-BN) layers (i.e., an h-BN/FTO wave pattern) on a glass substrate for use as an RF-transmitting heating system for anti- and de-icing. The FTO wave pattern and h-BN layer act as the heating element and heat spreader, respectively. The h-BN layer showed a transmittance of approximately 90% for RF waves on glass (X band: 8.2-12.4 GHz) (the 10% loss was attributable to the glass substrate). The differences in the temperatures of the FTO-patterned and non-patterned areas for the h-BN(3.6 nm)/FTO and FTO wave pattern were 19.3 and 25.5 °C, respectively. This means that the h-BN layer improved the heat-spreading performance by 6.2 °C. Furthermore, a de-icing test was performed using the h-BN(3.6 nm)/FTO wave pattern by applying a voltage of 40 V at -20 °C. The ice on the non-patterned area melted within 1 min while that on the FTO-patterned area melted within 30 s. These results suggest that the fabricated h-BN(3.6 nm)/FTO wave pattern for RF-transmitting heating systems is suitable for use with the radomes of drones, unmanned aerial vehicles, aircraft, and spaceships in extremely cold environments.