Tuning Geometry of SWCNTs by CO₂ in Floating Catalyst CVD for High‐Performance Transparent Conductive Films

Abstract

Optimized geometry of single‐walled carbon nanotubes (SWCNTs) is vital to high‐performance transparent conductive films (TCFs). Herein, the geometry of SWCNTs, i.e., tube diameter, bundle length, and bundle diameter, are successfully tuned by introducing carbon dioxide (CO2) into floating catalyst chemical vapor deposition (FC‐CVD), where carbon monoxide (CO) is used as a carbon source and ferrocene as a catalyst precursor. Both tube diameter and bundle length increase with an increment of CO2 concentration, and the yield of SWCNTs can be significantly promoted with the appropriate amount of CO2. The role of CO2 in this behavior is further rationalized as enhancing CO decomposition or carbon dissolution into catalysts. The TCFs based on SWCNTs with optimized geometry by CO2 exhibit improved performance up to 86.8 Ω sq−1 at 90% transmittance after AuCl3 doping, achieving about 50% reduction of sheet resistance compared to the TCFs without CO2. The use of CO2 for directly tuning growth of SWCNTs blazes a new trail in the field of SWCNT based TCFs.

Enhanced Tunneling in a Hybrid of Single-Walled Carbon Nanotubes and Graphene

“…[29][30][31] With the same approach, some of us have earlier demonstrated that SWCNT properties can be tuned by small changes in the composition of synthesis atmosphere. 31 In this work we used a composition that concurrently maximizes both the tube diameter and length, which according to earlier electron microscopy experiments correspond to 1.9±0.5 nm and 7.5±5.6 µm, respectively. 29 For optical and electrical characterization, the nanotube films were either accumulated directly on the target substrate by using a thermophoretic precipitator (TP) 32 or, for reference purpose, by vacuum filtration and presstransfer (see Figure 1b-c).…”

Roles of sulfur in floating-catalyst CVD growth of single-walled carbon nanotubes for transparent conductive film applications

“…Fe-FeCp2, CH4 indicating a strong universality of the process. Whereas c) Fe-spark, CO [86] produced SWCNTs without graphene flakes.…”

“…However, when we used carbon monoxide as a carbon source we were not able to produce simultaneously SWCNTs and graphene nano flakes. Typical examples are spark produced Fe catalyst [33] (5.22c) and ferrocene based Fe catalyst [86] along with CO as a carbon source as indicated in Table 5.1. The reason is CO cannot decompose itself without metal catalysts and is not a hydrocarbon which can produce poly aromatic hydrocarbons in the presence of high temperature.…”

High-performance transparent conducting films of long single-walled carbon nanotubes synthesized from toluene alone

“…To simply evaluate the optoelectronic performance of a TCF, the sheet resistance and film transmittance (T) at 550 nm are required. The sheet resistance and transmittance of a SWCNT TCF are affected by nanotube diameter [6], length [7] and crystallinity [8], as well as the diameter of the SWCNT bundle [9], film morphology [10], the amount of catalyst particles in the film [8] and the purity of semiconducting SWCNTs (s-SWCNTs) [11]. The optoelectronic performance of pristine SWCNT TCFs does not usually meet the requirements of practical device applications, which require a low sheet resistance combined with high transparency.…”

“…Ethanol (C2H6O) [10] has often been employed as the carbon source in producing SWCNTs, since this results in relatively high yield and a competitive TCF performance compared with using either carbon monoxide (CO) [6] or ethylene (C2H4) [13] as the carbon source. However, further improvements in SWCNT yields and in the optoelectronic performance of TCFs are required for large-scale applications.…”