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Solar cells that combine single-crystalline silicon (Si) with graphene (G) have been widely researched in order to develop next-generation photovoltaic devices. However, the power conversion efficiency (PCE) of G/Si solar cell without chemical doping is commonly low due to the relatively high resistance of graphene. In this work, through combining graphene with carbon nanotube (CNT) networks, we fabricated three kinds of hybrid nanocarbon film/Si heterojunction solar cells in order to increase the PCE of the graphene based Si solar cell. We investigated the characteristics of different nanocarbon film/Si solar cells and found that their performance depends on the heterojunctions. Specifically, a doping-free G-CNT/Si solar cell demonstrated a high PCE of 7.9%, which is nearly equal to the combined value of two individuals (G/Si and CNT/Si). This high efficiency is attributed to the synergistic effect of graphene and CNTs, and can be further increased to 9.1% after applying a PMMA antireflection coating. This study provides a potential way to further improve the Si based heterojunction solar cells.

Bridged strips consisting of carbon nanotubes and poly(vinylidene fluoride) are developed, which exhibit notable deflection in response to very low driven voltages (), because of both the excellent conductivity of the unique carbon nanotube film and the powerful thermal expansion capability of the polymer. The actuators demonstrate periodic vibrations motivated by the alternating signals. The amplitude of displacement is dependent not only on the driven voltage but also on the applied frequency. The mechanism of actuation is confirmed to be the thermal power induced by the electrical heating. By accelerating the dissipation of heat, the vibration response at higher frequencies can be significantly enhanced. The useful locomotion shows great promise in potential applications such as miniature smart devices and micro power generators.

Continuous CNT fibers have been directly fabricated in a speed of 50 m/h–400 m/h, based on an improved chemical vapor deposition method. As-prepared fibers are further post-treated by acid. According to the SEM images and Raman spectra, the acid treatment results in the compaction and surface modification of the CNTs in fibers, which are beneficial for the electron and load transfer. Compared to the HNO3 treatment, HClSO3 or H2SO4 treatment is more effective for the improvement of the fibers' properties. After HClSO3 treatment for 2 h, the fibers' strength and electrical conductivity reach up to ~ 2 GPa and ~ 4.3 MS/m, which are promoted by ~ 200% and almost one order of magnitude than those without acid treatment, respectively. The load-bearing status of the CNT fibers are analyzed based on the downshifts of the G ' band and the strain transfer factor of the fibers under tension. The results reveal that acid treatment could greatly enhance the load transfer and inter-bundle strength. With the HClSO3 treatment, the strain transfer factor is enhanced from ~ 3.9% to ~ 53.6%.

In this work, we have presented a freestanding and flexible CNT-based film with sheet resistance of 60 Ω/ and transmittance of 82% treated by nitric acid and chloroauric acid in sequence. Based on modified CNT film as a transparent electrode, we have demonstrated an ultrathin, flexible organic solar cell (OSC) fabricated on 2.5-μm PET substrate. The efficiency of OSC, combined with a composite film of poly (3-hexylthiophene) (P3HT) and phenyl-C61 butyric acid methyl ester (PCBM) as an active layer and with a thin layer of methanol soluble biuret inserted between the photoactive layer and the cathode, can be up to 2.74% which is approximate to that of the reference solar cell fabricated with ITO-coated glass (2.93%). Incorporating the as-fabricated ITO-free OSC with pre-stretched elastomer, 50% compressive deformation can apply to the solar cells. The results show that the as-prepared CNT-based hybrid film with outstanding electrical and optical properties could serve as a promising transparent electrode for low cost, flexible and stretchable OSCs, which will broaden the applications of OSC and generate more solar power than it now does.

An easily manipulative approach was presented to fabricate electrodes using free-standing single-walled carbon nanotube (SWCNT) films grown directly by chemical vapor deposition. Electrochemical properties of the electrodes were investigated. In comparison with the post-deposited SWCNT papers, the directly grown SWCNT film electrodes manifested enhanced electrochemical properties and sensitivity of sensors as well as excellent electrocatalytic activities. A transition from macroelectrode to nanoelectrode behaviours was observed with the increase of scan rate. The heat treatment of the SWCNT film electrodes increased the current signals of electrochemical analyser and background current, because the heat-treatment of the SWCNTs in air could create more oxide defects on the walls of the SWCNTs and make the surfaces of SWCNTs more hydrophilic. The excellent electrochemical properties of the directly grown and heat-treated free-standing SWCNT film electrodes show the potentials in biological and electrocatalytic applications.