Pressure‐Induced Polymerization and Electrical Conductivity of a Polyiodide

We report the high‐pressure structural characterization of an organic polyiodide salt in which a progressive addition of iodine to triiodide groups occurs. Compression leads to the initial formation of discrete heptaiodide units, followed by polymerization to a 3D anionic network. Although the structural changes appear to be continuous, the insulating salt becomes a semiconducting polymer above 10 GPa. The features of the pre‐reactive state and the polymerized state are revealed by analysis of the computed electron and energy densities. The unusually high electrical conductivity can be explained with the formation of new bonds.     

Selenium‐Substituted Diketopyrrolopyrrole Polymer for High‐Performance p‐Type Organic Thermoelectric Materials

Development of high‐performance organic thermoelectric (TE) materials is of vital importance for flexible power generation and solid‐cooling applications. Demonstrated here is the significant enhancement in TE performance of selenium‐substituted diketopyrrolopyrrole (DPP) derivatives. Along with strong intermolecular interactions and high Hall mobilities of 1.0–2.3 cm² V^?1 s^?1 in doping‐states for polymers, PDPPSe‐12 exhibits a maximum power factor and ZT of up to 364 μW m^?1 K^?2 and 0.25, respectively. The performance is more than twice that of the sulfur‐based DPP derivative and represents the highest value for p‐type organic thermoelectric materials based on high‐mobility polymers. These results reveal that selenium substitution can serve as a powerful strategy towards rationally designed thermoelectric polymers with state‐of‐the‐art performances.