Systematic Conversion of Single Walled Carbon Nanotubes into n-type Thermoelectric Materials by Molecular Dopants

Abstract

Thermoelectrics is a challenging issue for modern and future energy conversion and recovery technology. Carbon nanotubes are promising active thermoelectic materials owing to their narrow bandgap energy and high charge carrier mobility, and they can be integrated into flexible thermoelectrics that can recover any waste heat. We here report air-stable n-type single walled carbon nanotubes with a variety of weak electron donors in the range of HOMO level between ca. −4.4 eV and ca. −5.6 eV, in which partial uphill electron injection from the dopant to the conduction band of single walled carbon nanotubes is dominant. We display flexible films of the doped single walled carbon nanotubes possessing significantly large thermoelectric effect, which is applicable to flexible ambient thermoelectric modules.

Thermal energy harvesting for large-scale applications using MWCNT-grafted glass fibers and polycarbonate-MWCNT nanocomposites

“…In other words, the oxygen groups attached on the MWCNTs; carboxyl as well as hydroxyl, act as p-dopants rendering the MWCNTs p-type semiconductors with a high hole concentration (higher compared to unfunctionalized and hydroxyl functionalized MWCNTs). The results are is in very good agreement with observations from the literature, where doping by an acid treatment is shown to improve the Seebeck coefficients of MWCNTs [48,49]. The samples prepared with hydroxyl functionalized MWCNTs show only a slight improvement of the Seebeck coefficient compared to PC/u-MWCNT, due to the relative low amount of oxygen observed with the previously performed XPS analysis [42].…”

“…However, such high filler loadings may result also in a significant increase of thermal conductivity [15,26,27]. In addition, studies on carbon nanotubes (CNTs) only films (as bucky papers) have shown promising thermoelectric behavior which has been found to be related to the level of doping [28,29], as well as the dopant nature [30][31][32][33][34]. Doping of the SWCNTs by using e.g.…”

Photoinduced p‐ to n‐type Switching in Thermoelectric Polymer‐Carbon Nanotube Composites

“…[25][26][27][28][29] Their doping level, and concomitant Seebeck coeffi cient, can be tuned by doping electrically [ 30 ] or chemically with a variety of air-stable compounds. [ 31 ] Pure CNTs exhibit, however, a high thermal conductivity [ 32 ] and are difficult to process from solution. Using CNTs as conductive fi llers within polymer matrices may result in synergies, such as a high S and σ , while keeping κ low and allowing for easy processing.…”

Thickness-dependent thermoelectric power factor of polymer-functionalized semiconducting carbon nanotube thin films

“…In this context, several researchers have recently achieved such a thermoelectric property modulation using field effect and electrochemical transistor techniques [8–10]. We have also demonstrated the amphoteric (both p-type and n-type) chemical doping of SWNTs, achieving ambient stability and precise doping level control [11–16]. …”