Recent efforts are devoted to the investigation of operating mechanisms, new synthesis routes, new device architectures, stability of the organic materials, lifetime, encapsulation, etc.
Key words: P3HT, PCBM, organic photovoltaic, organic material
 Rowell, Michael W.; Topinka, Mark A.; McGehee, Michael D.; Prall, Hans-Jurgen; Dennler, Gilles; Sariciftci, Niyazi Serdar; Hu, Liangbing; Gruner, George Organic solar cells with carbon nanotube network electrodes, Appl Phys Lett, 88(23), 2006, 233506–233509
Iijima's discovery of multi-walled carbon nanotubes in the insoluble material of arc-burned graphite rods in 1991 and Mintmire, Dunlap, and White's independent prediction that if single-walled carbon nanotubes could be made, then they would exhibit remarkable conducting properties helped create the initial buzz that is now associated with carbon nanotubes. Nanotube research accelerated greatly following the independent discoveries by Bethune at IBM and Iijima at NEC of single-walled carbon nanotubes and methods to specifically produce them by adding transition-metal catalysts to the carbon in an arc discharge. The arc discharge technique was well-known to produce the famed Buckminster fullerene on a preparative scale, and these results appeared to extend the run of accidental discoveries relating to fullerenes. The original observation of fullerenes in mass spectrometry was not anticipated, and the first mass-production technique by Krätschmer and Huffman was used for several years before realizing that it produced fullerenes.
If a is generated by the application of a strong electric field during the growth process (plasma enhanced chemical vapor deposition*), then the nanotube growth will follow the direction of the electric field. By adjusting the geometry of the reactor it is possible to synthesize vertically aligned carbon nanotubes (i.e., perpendicular to the substrate), a morphology that has been of interest to researchers interested in the electron emission from nanotubes. Without the plasma, the resulting nanotubes are often randomly oriented. Under certain reaction conditions, even in the absence of a plasma, closely spaced nanotubes will maintain a vertical growth direction resulting in a dense array of tubes resembling a carpet or forest.
Of the various means for nanotube synthesis, CVD shows the most promise for industrial-scale deposition, because of its price/unit ratio, and because CVD is capable of growing nanotubes directly on a desired substrate, whereas the nanotubes must be collected in the other growth techniques. The growth sites are controllable by careful deposition of the catalyst. In 2007, a team from demonstrated a high-efficiency CVD technique for growing carbon nanotubes from . Researchers at Rice University, until recently led by the late Dr. Richard Smalley, have concentrated upon finding methods to produce large, pure amounts of particular types of nanotubes. Their approach grows long fibers from many small seeds cut from a single nanotube; all of the resulting fibers were found to be of the same diameter as the original nanotube and are expected to be of the same type as the original nanotube. Further characterization of the resulting nanotubes and improvements in yield and length of grown tubes are needed.
and carbon nanotubes are not necessarily products of high-tech laboratories; they are commonly formed in such mundane places as ordinary , produced by burning methane, ethylene, and benzene, and they have been found in from both indoor and outdoor air. However, these naturally occurring varieties can be highly irregular in size and quality because the environment in which they are produced is often highly uncontrolled. Thus, although they can be used in some applications, they can lack in the high degree of uniformity necessary to meet many needs of both research and industry. Recent efforts have focused on producing more uniform carbon nanotubes in controlled flame environments. Such methods have promise for large-scale, low-cost nanotube synthesis, though they must compete with rapidly developing large scale CVD production.
In 1979 John Abrahamson presented evidence of carbon nanotubes at the 14th Biennial Conference of Carbon at . The conference paper described carbon nanotubes as carbon fibers which were produced on carbon anodes during arc discharge. A characterization of these fibers was given as well as hypotheses for their growth in a nitrogen atmosphere at low pressures.
Nanotubes were observed in 1991 in the carbon soot of graphite during an arc discharge, by using a current of 100 , that was intended to produce fullerenes. However the first production of carbon nanotubes was made in 1992 by two researchers at 's Fundamental Research Laboratory. The method used was the same as in 1991. During this process, the carbon contained in the negative electrode sublimates because of the high discharge temperatures. Because nanotubes were initially discovered using this technique, it has been the most widely-used method of nanotube synthesis.
Single-walled nanotubes are still very expensive to produce, around $1500 per gram as of 2000, and the development of more affordable synthesis techniques is vital to the future of carbon nanotechnology. If cheaper means of synthesis cannot be discovered, it would make it financially impossible to apply this technology to commercial-scale applications. Several suppliers offer as-produced arc discharge SWNTs for ~$50–100 per gram as of 2007.
Cecile Reynaud has her expertise in the synthesis and chemical physics of nanomaterials. Her work has mainly dealt with silicon nanocrystals and aligned carbon nanotubes. She was for 15 years at the head of the Laboratory of Nanometric Assemblies (LEDNA) in the fundamental research division of Saclay CEA center. The LEDNA group follows the "bottom-up" approach of nanosciences. It develops its own synthesis methods and obtains nanostructured materials with well-controlled characteristics. The applications are relevant for energy, health, environmental issues and the development of composite materials. The group also develop the up-scaling of its processes to allow their industrial transfer.