Presentation on theme: "Dye-sensitised Solar Cells NVSES Nanotechnology 2014."— Presentation transcript:
Dye-sensitised Solar Cells NVSES Nanotechnology 2014
Some Questions 1. What units do we use to measure energy? 2. How much energy do humans use each year? 3. How is this likely to change? Why? 4. Where do we currently obtain our energy from? 5. What issues are related to our current energy production methods? 6. Where does nanotechnology fit into energy?
Depleting oil reserves Energy shortages as the world population increases Environmental pollution – especially oil spills. Supply of energy from the Sun to the Earth is gigantic: 321,024 joules per year, or about 10,000 times more than the global population currently consumes. Why should we be considering alternatives to fossil fuels?
What is the Photoelectric effect? When a surface is exposed to sufficiently energetic electromagnetic energy, light will be absorbed and electrons will be emitted. The threshold frequency is different for different materials. What does this mean?
French scientist in Edmund Becquerel in 1839 discovered the photoelectric effect. The photoelectric effect is the principle that drives all types of solar panel/photovoltaic cell 100 million watts of conventional solar cells are currently produced each year. How will the Photoelectric effect shape our future?
How does a silicon Solar panel work? They are based upon two types of silicon sandwiched together. One type of silicon is doped with an element or substance (phosphorus) having an extra electron (n-type) The other is doped with an element or substance (boron) having fewer electrons than silicon (p-type).
When a photon strikes the solar cell, an electron- hole pair is created. Before the electron-hole can be re-united, the electron is attracted to the n- type silicon and the hole is attracted to the p-type silicon.
Silicon is very expensive, energy intensive and high vacuum process required The panels are brittle and can not be shaped Panels need to be in direct sun light Current panels only use a small bandwidth of white light so efficiency is limited What issues do current solar panels have?
cheaper to make can be used on flexible surfaces can be shaped or tinted to suit domestic devices or architectural structures an electrolyte (liquid, gel or organic solid) can be used. So why consider nanocrystalline solar cells?
Nanocrystalline solar cells (Gratzel cell)
How do nanocrystalline cells work? What role does each component play? Nm3dZOTQoSgPZUuLbTa1 Nm3dZOTQoSgPZUuLbTa1
The dye layer adsorbs onto the TiO 2 A thin layer ensures that almost every electron is excited by the light and is rapidly transferred into the TiO 2 The titanium dioxide forms a rough semi conductor layer to increase the light absorption while allowing for efficient charge collection. The electrons are then transferred onto the conductive layer on the glass. Continued…
The positive charge is transferred from the dye to the iodide ( electron donor) The electron from the TiO 2 side of the cell reacts at the counter electrode and the iodide returns it to its original form. This creates a closed circuit and electricity is produced. What is the purpose of the counter electrode?
2 nd Hand Data Task Look at the data in the ‘2 nd hand data’ spreadsheet It isn’t very easy to form a conclusion is it? How might you convert the data so that it is easier to interpret?