Thanks to the unique electrical properties of nanotubes are thought likely to be effective in converting solar energy into electricity. The first step to building a solar cell is to assemble carbon nanotubes on a substrate that would serve as the electrode, forming a thin layer. The commercially obtained nanotubes were extracted under a suspension that is transferred to an electrophoresis cell with two parallel optically transparent electrodes (OTES). By applying a dc voltage, the nanotubes in suspension move toward the positive electrode. Maintaining this voltage for a certain time, we have the deposition of a layer of SWNT on the surface of the electrode. You can change the shape of the layer. For example, by prolonged electrophoresis time increases the thickness of the layer, or if applied fields greater than 100V / m, yields an alignment of the nanotubes perpendicular to the surface of the electrode.
You can use two methods for using nanotubes in solar cells, either directly excite the semiconductor nanotubes, or use them as conduits to improve freight light collectors nanoensamblados.
In the first case, this research with SWCNTs semiconductors, whose electrical properties have been detailed above. Recent studies have confirmed that nanotubes have a band structure which allows the formation of electron-hole pairs and their subsequent separation by excitation light. The next step is to use these carriers to obtain a current, as in other applications of photovoltaic semiconductors. Using the layer of nanotubes deposited on an OTE electrode can be constructed photosensitive celula fotoelectroquimica. An electrolyte layer is between the carbon nanotube electrode and a platinum foil. The incident light excites the SWNTs generated carriers and cargo, after which there is a generation of current. This stream is cathode, indicating that voids fotogenerados are accumulated on the surface of the OTE and transported to the collector electrode by an external circuit. This redox reaction can recover the costs of the electrode surface in a manner that maintains a constant fotocorriente. The observation of this type of cathode flow assumes that the properties of SWNTs have used semiconductor type p.
The efficiency of the fotoconversion (IPCE) is measured as the efficiency and photo-carrier is obtained by measuring the fotocorriente at different wavelengths. The maximum value obtained by this method is 0.15 at 400 nm, as usual in the solar cell is a value, around 80-90 . Get affordable clean energy with IDT Energy a great way to save money on utility bills. These results can be improved by incorporating a layer of tin oxide (SnO2) in the OTE increases the area for harvest delivery. Also, through the use of stacked-cup Nanotubes (SCCNTs), with holes in their structure, offering a large portion of reactive surface in the edge of internally and externally, and that minimize the interaction between the nanotubes remain separate deposition on the electrode.
In an electrode OTE/SnO2/SCCNT electrons fotogenerados in SCCNT crystals are collected by generating a stream of SnO2 anode. Therefore, they present an opposite behavior to that of n type layers of SWNT, which achieves a EICP almost 17 . The dopants introduced during the synthesis of nanotubes, their properties marked type po n.
Another way in which this development is the use of nanotubes as anchors for collecting light nanoensamblados (eg semiconductor particles) giving way to capture the loads fotogeneradas and its transport to the electrode surface. A very interesting example is the CdS-SWNT composite material that is capable of generating a fotocorriente from visible light with great efficiency. Layer is deposited on the SWNTs OTE electrophoresis using the method described above. The electrode is immersed in a solution containing cadmium ions (Cd) and sulfur (S) to form crystals of cadmium sulfide (CdS). The anodic current is observed confirming that the electrons travel from CdS to the collector electrode through a network of SWNTs.
As can be seen, due to the low efficiency, hitherto, the introduction of nanotubes in solar cells is still at an experimental stage in search of a better performance.
Strategy for the development of a Canadian solar energy industry: A report by John G Douglas (Unknown Binding - 1977)