Graphene-coated polypropylene (PP) textile fibers are presented for their use as temperature sensors. These temperature sensors show a negative thermal coefficient of resistance (TCR) in a range between 30 and 45 °C with good sensitivity and reliability and can operate at voltages as low as 1 V. The analysis of the transient response of the temperature on resistance of different types of graphene produced by chemical vapor deposition (CVD) and shear exfoliation of graphite (SEG) shows that trilayer graphene (TLG) grown on copper by CVD displays better sensitivity due to the better thickness uniformity of the film and that carbon paste provides good contact for the measurements. Along with high sensitivity, TLG on PP shows not only the best response but also better transparency, mechanical stability, and washability compared to SEG. Temperature-dependent Raman analysis reveals that the temperature has no significant effect on the peak frequency of PP and expected effect on graphene in the demonstrated temperature range. The presented results demonstrate that these flexible, lightweight temperature sensors based on TLG with a negative TCR can be easily integrated in fabrics.

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Aiming to increase carrier mobility in nanosheet-network devices, we have investigated MoS2-graphene composites as active regions in printed photodetectors.Combining liquid-exfoliation and inkjet-printing, we fabricated all-printed photodetectors with graphene electrodes and MoS2-graphene composite channels with various graphene mass fractions (0≤Mf≤16wt%). The increase in channel dark conductivity with Mf was consistent with percolation theory for composites below the percolation threshold. While the photoconductivity increased with graphene content, it did so more slowly than the dark conductivity such that the fractional photoconductivity decayed rapidly with increasing Mf. We propose that both mobility and dark carrier density increase with graphene content according to percolation-like scaling laws while photo-induced carrier density is essentially independent of graphene loading. This leads to percolation-like scaling laws for both photoconductivity and fractional photoconductivity, in excellent agreement with the data. These results imply that channel mobility and carrier density increase up to 100-fold on the addition of 16wt% graphene.Keywords: printed electronics, network devices, transistor 2The growing demand for low-cost electronics has sparked a wide investigation into printable, low-performance devices and circuits. The field has developed over the last 25 years from early demonstrations of solution processed devices 1, 2 to today's ability to print integrated circuitry. 3The most commonly studied materials in this area continue to be organic polymers and molecules which have been used to print in a range of devices, including light-emitting diodes and transistors. 3 However, these materials suffer a number of disadvantages including relatively low mobility and high cost. This has led a number of researchers to investigate the use of printed networks of inorganic nanoparticles and nanotubes in device applications. 4, 5While good device performance has been demonstrated from these materials (e.g. high mobilities and on:off ratios in printed transistors), it is not clear whether such technologies can be scaled at low cost due to difficulties in materials synthesis and processing.More recently, it has been shown that 2-dimensional nanosheets are promising candidates for electronic device applications, with single-nanosheet transistors displaying relatively high mobilities and on/off ratios. 6,7 In the context of printed electronics, fabricating printed nanosheet network-based devices will require access to nanosheet-containing inks.Critically, nanosheets can be produced cheaply in a form amenable to ink formulation by techniques such as liquid-phase exfoliation (LPE). 8,9 This method uses scalable processes, such as high shear mixing, 9 to exfoliate layered crystals into few-layer nanosheets in appropriate liquids. Using simple, centrifugation-based, post-processing techniques, it is possible to sizeselect the nanosheets while simultaneously exchanging the solvent and increasing the concent...

The alteration of graphene's electrical properties through chemical functionalization is a necessary process in order for graphene to fulfill its potential as a transparent conducting electrode. In this work, we present a method for the transfer and intercalation of large area (wafer scale) graphene samples to produce highly doped FeCl 3 intercalated Few Layer Graphene (FeCl 3 -FLG). Given its excellent flexibility, transmission, and a sheet resistance, comparable to that of Indium Tin Oxide, FeCl 3 -FLG has potential to replace alternative flexible transparent electrodes as well as compete with rigid transparent electrodes. We assess the effect of functionalization temperature on the degree of intercalation in the large area samples and comparing results to that of 1 cm 2 FeCl 3 -FLG samples. Raman spectroscopy is then used to characterize samples, where we introduce a new figure of merit ( PosG ) by which to assess the degree of intercalation in a sample. This is an average G peak position, weighted by the areas of the constituent peaks, which can then be used to map the charge carrier concentration of the sample. The inhomogeneity of the graphene grown by chemical vapor deposition is found to be one of the limiting factors in producing large area, high quality FeCl 3 -FLG.

In this paper, we present the first organic photovoltaic (OPV) devices fabricated with FeCl3 intercalated few layer graphene (i-FLG) electrodes. i-FLG electrodes were first fabricated and characterized by electrical and spectroscopic means, showing enhanced conductive properties compared to pristine graphene. These electrodes were then used in the fabrication of OPV devices and tested against devices made with commercially available Indium Tin Oxide (ITO) electrodes. Both types of device achieved similar efficiencies, while the i-FLG based device exhibited superior charge transport properties due to the increase in work function characterizing i-FLG. Both types of device underwent a stability study using both periodic and continuous illumination measurements, which revealed i-FLG based OPVs to be significantly more stable than those based on ITO. These improvements are expected to translate to increased device lifetimes and a greater total energy payback from i-FLG based photovoltaic devices. These results highlight the potential benefits of using intercalated graphene materials as an alternative to ITO in photovoltaic devices.