No abstract

Ionic liquids modulated PEDOT films with synergistically enhanced thermoelectric and mechanical performances have promising applications in vigorous wearable electronics and IoT sensors.

Low‐cost, non‐toxic, abundant organic thermoelectric materials are currently under investigation for use as potential alternatives for the production of electricity from waste heat. While organic conductors reach electrical conductivities as high as their inorganic counterparts, they suffer from an overall low thermoelectric figure of merit (ZT) due to their small Seebeck coefficient. Moreover, the lack of efficient n‐type organic materials still represents a major challenge when trying to fabricate efficient organic thermoelectric modules. Here, a novel strategy is proposed both to increase the Seebeck coefficient and achieve the highest thermoelectric efficiency for n‐type organic thermoelectrics to date. An organic mixed ion–electron n‐type conductor based on highly crystalline and reduced perylene bisimide is developed. Quasi‐frozen ionic carriers yield a large ionic Seebeck coefficient of −3021 μV K−1, while the electronic carriers dominate the electrical conductivity which is as high as 0.18 S cm−1 at 60% relative humidity. The overall power factor is remarkably high (165 μW m−1 K−2), with a ZT = 0.23 at room temperature. The resulting single leg thermoelectric generators display a high quasi‐constant power output. This work paves the way for the design and development of efficient organic thermoelectrics by the rational control of the mobility of the electronic and ionic carriers.

The development of pure organic magnets with high Curie temperatures remains a challenging task in material science. Introducing high‐density free radicals to strongly interacting organic molecules may be an effective method to this end. In this study, a solvothermal approach with excess hydrazine hydrate is used to concurrently reduce and dissolve rigid‐backbone perylene diimide (PDI) crystallites into the soluble dianion species with a remarkably high reduction potential. The as‐prepared PDI powders comprising radical anion aggregates are fabricated by a subsequent self‐assembly and spontaneous oxidation process. The results of magnetic measurements show that the PDI powders exhibit room‐temperature ferromagnetism and a Curie temperature higher than 400 K, with a vast saturation magnetization that reaches ≈1.2 emu g−1. Elemental analysis along with the diamagnetic signal of the ablated residue are used to rule out the possibility that the magnetism is due to metal contamination. The findings suggest that the long‐range ferromagnetic ordering can survive at room‐temperature in organic semiconductors, and offers a new optional way to create room‐temperature magnetic semiconductors.

It is generally considered that photoacoustic imaging (PAI) and fluorescence imaging (FLI) cannot be enhanced concurrently, as they are dependent on competitive photophysical processes at the single-molecule level. Herein, we reveal that BDTR9-OC8 and BDTR9-C8, which have identical π-conjugated backbones but are substituted by side chains of different rigidity, show distinct phototheranostic properties in the aggregated state. The NIR-II FLI and PAI brightness of BDTR9-C8 nanoparticles are enhanced by 4.6 and 1.4 times compared with BDTR9-OC8 nanoparticles. Theoretical calculations and GIWAXS analysis revealed that BDTR9-C8 with rigid side chains shows a relative amorphous condensed state, which will benefit the efficient transportation of photo-generated excitons and phonons, subsequently enhancing the FLI and PAI signals. Besides, both nanoparticles exhibit excellent photothermal conversion efficiency due to their strong light-harvesting capability and are considered effective photothermal therapy materials. This work provides an illuminating strategy for material design in the future.