Nanotechnology in solar cellsand its development
Outlines1.Introduction2.History3.Nanoparticles used for solarcells4.Process of development of solarcells5.Applications of solar cells6.Advantages7.Disadvantages8.Conclusion
Introduction1. Solar Energy is the energy received from the sun thatsustains life on earth.2. solar energy has been considered as a huge source ofenergy and also an economical source of energy because itis freely available.3. Solar energy is also using in cooking, heating, automobile,electronics, cooling, lighting, space technology and forcommunications among other uses.4. Represents the entire electromagnetic radiation (visiblelight, infrared, ultraviolet, x-rays, and radio waves).5. In fact, fossil fuels are also one of solar energy stored inorganic matter.6. Solar energy has increased in its importance to industriesand homes.7. Surface on the Earth’s orbit, normal to the sun, solarradiation hits at the rate of 1,366 Watt Per Meter Square.
1) These structureshave greatpotential foroptoelectronicapplications, one ofwhich may be solarcells2) Clean, renewablesource of energy3) Harnessed by solarcollection methodssuch as solar cells4) Converted intousable energy suchas electricityPhotovoltaic (solar) panelSet of solar panel
Historyi. 1839: French physicist Antoine-Cesar Becquerelobserved that shining light on an electrode submergedin electrolyte would create an electric current.ii. 1941: American Russell Ohl invented a PN junction ofsilicon solar cell.iii. The dye sensitized solar cell was developed in 1992 byGraetzel (EPFL, Laussane, Switzerland) and utilizesnanocrystalline TiO2 as the photo absorber.
Nanotechnolgy used for solar cells1. Nanotechnology in hybrid solar cells design could furtherimprove the performance and reduce the cost of PV cells andmodules.2. Basic principles, mechanism and challenges within three keyareas of nanotechnology have been discussed from a cleanenergy prospective.3. Nanotechnology might be able to increase the efficiency ofsolar cells, but the most promising application ofnanotechnology is the reduction of manufacturing cost.4. The nanorods behave as wires because when they absorblight of a specific wavelength they generate electrons.5. These electrons flow through the nanorods until they reachthe aluminium electrodes where they are combined to form acurrent and are used as electricity.
PHOTOVOLTAIC CELLSTraditional photovoltaic cells1. Mono or multi crystallinesilicon solar cells2. Multi junctionconcentrator solar cells3. Amorphous silicon/ siliconhetero junction cells4. Thin film solar cellsNanotech based photovoltaiccells1. Nanotubes2. Quantum dots3. Hot carrier solar cells4. Nanotech photovoltaicsolar cells5. Nanorods/ nanowiressolar cells
Traditional photovoltaic cellsA. Extensive research has been performedwith crystalline, multicrystalline , thin filmpolycrystalline and amorphous solar cellsto maximize cell efficiency as well as toreduce material size and cost.B. Thin film CIGS technology is verypromising for high efficiency at economicprice.C. Nanopareticles of Cu, In, and Ga oxide iscoated on a Mo foil or a non conductingsubstrate, improving cell efficiency to 8.9%on polyimide 13.0% on Mo foil and 13.6%on glass substrate.D. Mono or Multi crystalline silicon solar cellshave three wafer properties- 1)Lifetime2) Thickness 3)Resistivity.Traditional photovoltaic cells
Nanotech based photovoltaic cellsThe nanotech based solar cell isknown as third generationphotovoltaic cells is directed towardsabsorbing more sunlight by the use ofnanotechnology, e.g. nanotubes,quantum dots and hot carrier solarcells.Implementation of thesenanotechnologies in thesolar cell design is a real challenge.Figure is showingDye sensitized photovoltaic cells
NanotubesNanotubes are basically known as carbon nanotubesIn the photovoltaic cells technology, the nanometer scale tubes, coated by the specialp-type and n-type semiconductor junction materials, can generate electric current,which would we increased the surface area available to produce electricity.Figure showing the sensitization of polymer nanotube solar cellSource: Kymakis, E.; et,.al. Photovoltaic Cells Based on Dye-sensitisation of Single-wall Carbon Nanotubes in aPolymer Matrix, Science Direct, Solar Energy Materials and Solar Cells, 2003, vol. 80, pp. 465 –472.
Quantum dotsI. Quantum dots are semi-conducting crystalsof nanometer dimension, modeling into avariety of different forms with a tunablebond gap energy levels that behave as aspecial Class of semiconductors.II. A solar cell with the generator bond gapof semiconductor absorbs more energeticphotons causing the greater out put voltage.
Light Absorption of Quantum Dots – Comparison ofα versus Energy for Bulk Material and Quantum Dot7
Hot carrier solar cellsThe most challenging approach of generating electricity fromsunlight is hot carrier solar cells.The hot carrier solar cells, which utilize selective energy contactsto extract light generated hot carriers from semiconductorregions .Hot carrier solar cells convert their excess energy to heat intosemiconductor lattice.The optimizing both extraction energy and the bond gap of theabsorber .The hot carrier solar cell achieves very high efficiency.According to ROSS and NOZIK the efficiency limit of 66% for a hotcarrier conversion system is grater than an idealthermal system 52%, and for a quantum system.The chemical potential of a excited and is negative which reducesradiation losses, and permits a low threshold energy.
Hot carrier solar cellsHot carriers are collected before they thermelize
Energy gapEfficiency(%)Efficiency of a hot-carrier solar cell under: (a) direct (highlyconcentrated blackbody radiation) and (b) diffuse (non-concentratedblackbody radiation) for the case where the chemical potential
Process of development of nano solar cellsPhotovoltaic cells arecapable of directlyconverting sunlight intoelectricity.A simple wafer of siliconwith wires attached to thelayers. Current is producedbased on types of silicon(n- and p-types) used forthe layers. Each cell=0.5volts.Battery needed asstorageNo moving parts dono wear out, but becausethey are exposed to theweather, their lifespan isabout 20 years.
p-n junctionp-doped semiconductor is relatively conductive. The same is true of ann-doped semiconductor, but the junction between them canbecome depleted of charge carriers, and hence non-conductive,depending on the relative voltages of the two semiconductor regions.
p-n junction in thermal equilibrium with zero bias voltage applied.Electron and holes concentration are reported respectively with blueand red lines. Gray regions are charge neutral. Light red zone ispositively charged. Light blue zone is negatively charged.
1)The application of a positive bias on the p-type end will lead aPN junction into the forward biased mode of operation.2)Positive biases lower the bands in p region. As a result,electrons in an n region and holes in a p region will have smallerbarriers to overcome and diffuse to the other side.3)This leads to a shrinking depletion region and increasedconductivity.
Nanotechnology Thin-filmSolar Cells Publications byCountries [Science CitationIndex, 2001-08 (part-year)]Percentage of NanotechnologyThin-film Solar cells Publicationsby Country for Selected Years.
Nano-structured ZnO thin film solar cells publication by countries and years
Activity and diversity of top 10 countries innanotechnology thin film solar cells publications
APPLICATIONS OF NANO SOLAR CELLS• Heating of water• Cooling• Automobile• Communication• Energy• EnvironmentCOMMON APPLICATIONSSOME PROFESSION APPLICATIONS1)Ocean navigation aids: many lighthouses and most buoys are now powered by solar cells.2)Telecommunication systems: radio transceiverson mountain tops, or telephone boxes inthe country can often be solar powered.
3) Remote monitoring andcontrol: scientific researchstations, seismic recording, weatherstations, etc. use very little powerwhich, in combination with adependable battery, is providedreliably by a small PV module.4) Cathodic protection: this is amethod for shielding metal work fromcorrosion, for example, pipelines andother metal structures. A PV system iswell suited to this application since aDC source of power is required inremote locations along the path of apipeline.
Advantages of nano solar cells1. The power source of the sun is absolutely free.2. The production of solar energy produces no pollution.3. The technological advancements in solar energy systems have madethem extremely cost effective.4. Systems do not require any maintenance during their lifespan, whichmeans you never have to put money into them.5. Most systems have a life span of 30 to 40 years.6. Most systems carry a full warranty for 30 to 35 years or more.7. Unlike traditional monstrous panel systems, many modern systems aresleeker such as Uni-Solar rolls that lay directly on the roof like regularroofing materials.8. Nano solar energy can be fed back to the utilities to eliminate the needfor a storage system as well as eliminating or dramatically reducingyour electric bills.9. Solar energy systems are now designed for particular needs.
Disadvantages of nano solar cellsSilver is the best conductor of electricity having very lowresistance and increases its efficiency.The entire process of manufacture is still very expensive assilver is used for interconnection of these cells in the panel,which is a very expensive metal.Practical problem linked with the use of solar cell panels isregarding the storage of electricity general by themNano solar cell are producing DC electric. Nano solar cellsare not producing AC electric.
ConclusionThe development of an emerging technology,nanotechnology solar cells, such as thin film solarcells.Nanotechnology thin film solar cells as of mid2008. Based on science citation index. The US alsoleads in term of citation intensity of itspublications a measure of impact or quality.Comparing the leading in research in thisemerging technology finds today’s unusualaspects – JAPAN, GERMANYand CHINA.