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Improving charge insertion into intercalation hosts is essential for crucial energy and memory technologies. The layered material TiS2 provides a promising template for study, but further development of this compound demands improvement to its ion kinetics. Here, we report the incorporation of Se atoms into TiS2 nanobelts to address barriers related to sluggish ion motion in the material. TiS1.8Se0.2 nanobelts are synthesized through a solid-state method, and structural and electrochemical characterizations reveal that solid solutions based on TiS1.8Se0.2 nanobelts display increased interlayer spacing and electrical conductivity compared to pure TiS2 nanobelts. Cyclic voltammetry and electrochemical impedance spectroscopy indicate that the capacitive behavior of the TiS2 electrode is improved upon Se incorporation, particularly at low depths of discharge in the materials. The presence of Se in the structure can be directly related to an increased pseudocapacitive contribution to electrode behavior at a low Li+ content in the material and thus to improved ion kinetics in the TiS1.8Se0.2 nanobelts. 

Self-doping is an essential method of increasing carrier concentrations in organic electronics that eliminates the need to tailor host—dopant miscibility, a necessary step when employing molecular dopants. Self-n-doping can be accomplished using amines or ammonium counterions as an electron source, which are being incorporated into an ever-increasingly diverse range of organic materials spanning many applications. Self-n-doped materials have demonstrated exemplary and, in many cases, benchmark performances in a variety of applications. However, an in-depth review of the method is lacking. Perylene diimide (PDI) chromophores are an important mainstay in the semiconductor literature with well-known structure-function characteristics and are also one of the most widely utilized scaffolds for self-n-doping. In this review, we describe the unique properties of self-n-doped PDIs, delineate structure-function relationships, and discuss self-n-doped PDI performance in a range of applications. In particular, the impact of amine/ammonium incorporation into the PDI scaffold on doping efficiency is reviewed with regard to attachment mode, tether distance, counterion selection, and steric encumbrance. Self-n-doped PDIs are a unique set of PDI structural derivatives whose properties are amenable to a broad range of applications such as biochemistry, solar energy conversion, thermoelectric modules, batteries, and photocatalysis. Finally, we discuss challenges and the future outlook of self-n-doping principles.