Ionic-Liquid Doping of Carbon Nanotubes with [HMIM][BF<SUB>4</SUB>] for High Performance Flexible Thermoelectric Generators
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초록
내용
To exploit suitable carbon nanotube (CNT)-based thermoelectrics (TE) materials, doping of CNTs is an essential requirement to improve TE properties. Interfacial adsorption structure of the dopants onto surface of CNTs could affect to charge transfer behavior. Here, we introduce an imidazolium-based ionic liquid as a dopant of CNTs and investigate doping mechanisms at different CNT surface states. The cations are selectively adsorbed at the negatively charged CNT surface, forming the cation-rich layer nearby the CNT surface. In contrast, at the relatively neutral CNT surface both cations and anions can approach without preference. With the distinctive molecular adsorptions, each case shows different doping characteristics that p-doping by the former case and n-doping by the latter case. Finally, optimized CNT films exhibit high p-type TE power factors up to 762 μW m−1 K−2 and flexible TE generators are successfully fabricated showing the output power of 6.8 μW and voltage of 334 mV.