Synergistic Interactions in Sequential Process Doping of Polymer/Single‐Walled Carbon Nanotube Nanocomposites for Enhanced n‐Type Thermoelectric Performance

• Published in: Small (Weinheim an der Bergstrasse, Germany) Vol. 20; no. 9; pp. e2306166 - n/a
• Main Authors: Lin, Po‐Shen, Lin, Jhih‐Min, Tung, Shih‐Huang, Higashihara, Tomoya, Liu, Cheng‐Liang
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01.03.2024
• Subjects: carbon nanotubes; conjugated polymers; Diimide; Doping; Nanocomposites; Naphthalene; n‐type doping; Polymers; Power factor; Seebeck effect; Single wall carbon nanotubes; thermoelectric; Thermoelectric generators; Thermoelectricity; thermoelectric; carbon nanotubes; nanocomposites; n-type doping; conjugated polymers
• ISSN: 1613-6810; 1613-6829; 1613-6829
• DOI: 10.1002/smll.202306166

This study focuses on the fabrication of nanocomposite thermoelectric devices by blending either a naphthalene‐diimide (NDI)‐based conjugated polymer (NDI‐T1 or NDI‐T2), or an isoindigo (IID)‐based conjugated polymer (IID‐T2), with single‐walled carbon nanotubes (SWCNTs). This is followed by sequential process doping method with the small molecule 4‐(2,3‐dihydro‐1,3‐dimethyl‐1H‐benzimidazol‐2‐yl)‐N,N‐dimethylbenzenamine (N‐DMBI) to provide the nanocomposite with n‐type thermoelectric properties. Experiments in which the concentrations of the N‐DMBI dopant are varied demonstrate the successful conversion of all three polymer/SWCNT nanocomposites from p‐type to n‐type behavior. Comprehensive spectroscopic, microstructural, and morphological analyses of the pristine polymers and the various N‐DMBI‐doped polymer/SWCNT nanocomposites are performed in order to gain insights into the effects of various interactions between the polymers and SWCNTs on the doping outcomes. Among the obtained nanocomposites, the NDI‐T1/SWCNT exhibits the highest n‐type Seebeck coefficient and power factor of −57.7 µV K−1 and 240.6 µW m−1 K−2, respectively. However, because the undoped NDI‐T2/SWCNT exhibits a slightly higher p‐type performance, an integral p–n thermoelectric generator is fabricated using the doped and undoped NDI‐T2/SWCNT nanocomposite. This device is shown to provide an output power of 27.2 nW at a temperature difference of 20 K. The chemical structures of various conjugated polymers affect the doping process in polymer/single‐walled carbon nanotube (SWCNT) nanocomposites with 4‐(2,3‐dihydro‐1,3‐dimethyl‐1H‐benzimidazol‐2‐yl)‐N,N‐dimethylbenzenamine (N‐DMBI). The successful doping outcomes are attributed to strong polymer‐dopant interaction, coupled with a moderate polymer‐SWCNT interaction . Under a temperature difference of 20 K, a p–n integrated thermoelectric generator with ten legs generates an output power of 27.2 nW.