PSS. The single-walled carbon nanotube organic solar cell in this work shows a power conversion efficiency of 6.04%. This value is 83% of the leading ITO-based device performance (7.48%). Flexible application shows 3.91% efficiency and is capable of withstanding a severe cyclic flex test.

By using the excellent optical and electrical properties of pristine SWNTs with long bundle lengths, we present single-walled carbon nanotube-silicon (SWNT/Si) solar cells of 11% power conversion efficiency (PCE), prepared without doping. The PCEs of the fabricated solar cells even increased slightly after 10 months of exposure to ambient conditions, without any external protection. The open-circuit voltage of the SWNT/Si solar cells under low light intensities, down to 10 mW cm À2 , demonstrated the characteristics of the ideal p-n junction model. The mechanism was discussed, taking into account the effect of varying the interfacial oxide layer thickness between the SWNTs and Si on the solar cell's performance. The high efficiency and stability demonstrated in this study make SWNT/Si solar cells one of practical choices for next generation energy system.

We synthesize vertically aligned single-walled carbon nanotubes (VA-SWNTs) with subnanometer diameters on quartz (and SiO2/Si) substrates by alcohol CVD using Cu-anchored Co catalysts. The uniform VA-SWNTs with a nanotube diameter of 1 nm are synthesized at a CVD temperature of 800 °C and have a thickness of several tens of μm. The diameter of SWNTs was reduced to 0.75 nm at 650 °C with the G/D ratio maintained above 24. Scanning transmission electron microscopy energy-dispersive X-ray spectroscopy (EDS-STEM) and high angle annular dark field (HAADF-STEM) imaging of the Co/Cu bimetallic catalyst system showed that Co catalysts were captured and anchored by adjacent Cu nanoparticles, and thus were prevented from coalescing into a larger size, which contributed to the small diameter of SWNTs. The correlation between the catalyst size and the SWNT diameter was experimentally clarified. The subnanometer-diameter and high-quality SWNTs are expected to pave the way to replace silicon for next-generation optoelectronic and photovoltaic devices.

We propose a water vapor treatment to direct the formation of single-walled carbon nanotubes (SWNTs) into a self-assembled microhoneycomb network (μ-HN) for the application to SWNT-Si solar cells. The μ-HN consists of vertical aggregated SWNT walls and a buckypaper bottom. This hierarchical structure exhibits lower sheet resistance and higher optical transmittance compared with buckypaper. The pristine μ-HN SWNT-Si solar cell shows a record-high fill factor of 72% as well as a power conversion efficiency (PCE) of 6% without optimizing the diameter or height of the vertically aligned SWNTs. The PCE remains stable for weeks under ambient condition, and a PCE exceeding 10% is achieved in the dry state after dilute nitric acid treatment.

This study reports a scalable and room‐temperature solid‐state redox functionalization process for single‐walled carbon nanotubes (SWNTs) with instant efficacy and high stability. By drop‐casting/spin‐coating CuCl2/Cu(OH)2 colloidal ethanol solution onto SWNT films, the sheet resistance of the SWNT films achieves 69.4 Ω sq−1 at 90% transparency without noticeable increase for more than 12 months. The charge transfer mechanism between the redox and the SWNTs is revealed by Raman and X‐ray photoelectron spectroscopies. The SWNT/silicon solar cells are utilized as a benchmark to evaluate the effectiveness of the redox functionalization process and its compatibility for device integration. The power conversion efficiency of the SWNT/Si solar cell increases by 115% after redox functionalization, reaching the value of 14.09% without degradation in the ambient for over 12 months. Temperature‐dependent operation characteristics of the redox functionalized SWNT/Si solar cells demonstrate that the Fermi level unpinning and enhanced tunneling of the charge carriers contribute to the significant improvement of the photovoltage and fill factor. The CuCl2/Cu(OH)2 redox also serves as an antireflection layer, resulting in a 20% increase of the photocurrent. The proposed redox functionalized SWNTs are promising as multifunctional transparent conductive films for wide‐range solar cell applications.

Passive oxide layers on metal substrates impose remarkable interfacial resistance for electron and phonon transport. Here, a scalable surface activation process is presented for the breakdown of the passive oxide layer and the formation of nanowire/nanopyramid structured surfaces on metal substrates, which enables high-efficiency catalysis of high-crystallinity carbon nanotubes (CNTs) and the direct integration of the CNT–metal hierarchical architectures with flexible free-form configurations. The CNT–metal hierarchical architecture facilitates a dielectric free-energy-carrier transport pathway and blocks the reformation of passive oxide layer, and thus demonstrates a 5-fold decrease in interfacial electrical resistance with 66% increase in specific surface area compared with those without surface activation. Moreover, the CNT–metal hierarchical architectures demonstrate omnidirectional blackbody photoabsorption with the reflectance of 1 × 10–5 over the range from ultraviolet to terahertz region, which is 1 order of magnitude lower than that of any previously reported broadband absorber material. The synergistically incorporated CNT–metal hierarchical architectures offer record-high broadband optical absorption with excellent electrical and structural properties as well as industrial-scale producibility.

Carbonassisted catalyst pretreatment enables straightforward synthesis of high-density carbon nanotube forests. Carbon

Model-informed experiments reveal that cellular pattern formation in capillary-densified aligned carbon nanotube arrays is governed not only by their height, but also by substrate adhesion strength.