Nanotechnology in solar cells

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Abstract

Photovoltaic technology is relatively the most reliable source of energy in which fluctuations in power output stability is minimal. As a result, they are likely to be the best bet for powering futuristic means of transport such as Elon Musk’s Hyperloop or smart electronic devices in place of the rechargeable battery. Unfortunately, efficiency in this mode of energy generation is very minimal and the cost of manufacturing machinery, as well as raw materials, is quite high. Fortunately, the use of nanotechnology can reduce the burden of installation costs by replacement of the rather expensive silicon material with Nanorod material structures. Nanotechnology promises to reduce the cost associated with photovoltaic cells and effectively replacing them with better carbon material which can be utilized in smaller devices. Several techniques of how nanotechnology is applied in solar cells exist.

Introduction

Solar energy is one of the simplest forms of energy generation using light energy only. Commonly referred to as photovoltaic cells, the principle behind this mechanism is such that light photons received by a photovoltaic material energize valence electrons of the semiconductor material. If the energy is high enough to move the electrons into the conduction band, then the electron movement results in electricity. Since the conduction band is always of high electric conductivity, the electrons generated are readily conducted and stored as solar energy. However, this technology requires further innovation to minimize the large wastage due to differences in material properties. This explains why there are innovations for instance which involve material science to try and dye the material for effective energy management.

Some materials have a higher energy band gap which requires stronger light photons to excite valence electrons into the conduction band. Unfortunately, still, materials with a lower band gap can only produce a lower output. From research and experiments around the field, the optimal output voltage for a solar cell which also serves as the most efficient balance between band gap energy and voltage output is one that produces up to around 1.4eV (Tiwari, A., Boukherroub, R., Sharon, M., & Richardson, R. 2014). Even with this precision optimization in the industry still, more than 60% of the energy from light is lost. Moreover, photovoltaic cells are generally very expensive both in design, manufacture and hence implementation (European Commission, 2011). For efficiency in charge collection from the silicon material, there is a need for a very pure charge collecting material to avoid recombination centres an engineering and scientific fit that is not very easy to achieve with the current silicon material (Wu, B., Mathews, N., & Sum, T. C., 2017). Nanotechnology promises to solve this challenges in various ways.

Nanorods as a Substitute for Silicon

Scientists have successfully used carbon Nanorods which are plastic in nature to produce wire-like structures dispersed within a polymer and that also conduct electricity for use in low power devices (Luque, A., & Mellor, A. V., 2015). The Nanorods work in the same way as wires only that they are capable of absorbing photons from a specific wavelength and generate electrons which move towards a conducting aluminium electrode as current.

Even though this Nanorod can only generate up to 0.7 volts, there are more advantages that accompany them (Tiwari, 2014). First, the cells can be easily produced in mass due to the possibility of application in separate coatings. Secondly, the rods are not made of silicon and there manufacture does not use complex machinery and equipment. Consequently, this makes them more efficient in custom low power device applications which are in everyday equipment. They can easily be painted onto a surface and used to generate electricity without complex manufacturing casing involved (European Commission, 2011).

Various Nanotechnology Applications in Solar Cells

There are Nanoscale techniques which help to improve solar efficiency. A surface adsorbed dye inform of a nanoparticle is used in dye-sensitized solar cells (European Commission, 2011). These cells have a charge separation interface where a chemical potential influences the flow of charges thus eliminating the need for pure silicon material that reduces charge recombination centres (Wu, 2017).

Other solar cell technologies take advantage of polymers which are made basically from Nanoscale materials thus forming the common bulk heterojunction polymer solar cells. The polymers absorb light and cause charge separation at the interface of the carbon fullerenes. Current then flows through the conductive carbon polymer material using either hole transport technique or the electron transport (Wu, 2017). The benefits of this technique are numerous. It is easier for the technique to be used due to insensitivity to impurities which makes it more efficient. Furthermore, quantum confinement can be applied together with the technique (Luque, 2015). Reverse auger process which is the creation of multiple excitations of the solar cell regions to ensure more efficiency in energy capture over a small area of the cell.

Identified Challenges

Research activity surrounding solar cells show evidence that it is a powerful source of energy for application in futuristic innovations. However, the challenges facing the industry limit further advances unless a revolutionary innovation on efficiency is identified. While nanotechnology helps to minimize the cost of manufacturing of photovoltaic cells, still, the challenge with efficiency in energy production still abounds. Nanotechnology solves material cost implications of silicon, but currently, they are only applicable to low power devices which makes it difficult for large-scale consumption (Tiwari, 2014). With large-scale breakthroughs, there is a high possibility for a revolutionary technology that will reduce the cost of solar installation and hence replace fossil fuel use.

Internet Research Results

Passive luminescent solar concentrators is an innovation that has two major problems whose solution can be addressed using nanotechnology in solar cells. The principle of total internal reflection of light as in a prism or fibre optic rods is applied to concentrate light towards highly efficient photovoltaic cells (European Commission, 2011). Unfortunately, this is subject to internal absorption of light and luminescence quantum yield defined by the ratio of the number of photons emitted divided by the photons absorbed in a material that produces light without being heated (European Commission, 2011). This can be easily solved using nanotechnology in which two shells of Nanorods can be used. In this case, the energy is moved from the absorbing Nanorods which are made of cadmium compounds to larger Nanorods (Luque, 2015). Basically, spectral differences between blue absorption and emission of red light cause minimization of self-absorption.

Conclusion

It can be concluded that nanotechnology applications in solar cells are vast and the possibilities are limitless. Current nanotechnologies used in solar cells include for instance the use of carbon Nanorods dispersed in polymers as an alternative for the more expensive version of the silicon semiconductor material. Also, dyeing solar cell materials to generate dye-sensitized solar cells make it possible to improve the solar cell efficiency. Nanotechnology also helps to address the two main challenges in passive luminescent solar concentrators. The only challenge facing nanotechnology in solar cells which also affects current photovoltaic technology is how to ensure efficiency in energy conversion from light to electricity.

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  1. European Commission. (2011). Photovoltaics and nanotechnology, from innovation to industry: The European photovoltaics clusters. Luxembourg: EUR-OP.
  2. Luque, A., & Mellor, A. V. (2015). Photon Absorption Models in Nanostructured Semiconductor Solar Cells and Devices. Cham: Springer International Publishing.
  3. Tiwari, A., Boukherroub, R., Sharon, M., & Richardson, R. (2014). Solar cell nanotechnology.
  4. Wu, B., Mathews, N., & Sum, T.-C. (2017). Plasmonic Organic Solar Cells: Charge Generation and Recombination.
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