Skip to 0 minutes and 3 secondsThe animation you're about to see describes the steps involved in converting Photon Energy to electrical energy in a typical dye-sensitised solar cell.

Skip to 0 minutes and 15 secondsIt starts with the TIO2 layer which consists of billions of nano particles providing a large surface area about 1000 times larger than what you can see. TIO2 is a common chemical found in paints, sunscreen and even a cup noodles. A single layer of pigment, a dye, is attached to this large surface area electrode which promotes very strong harvesting of sunlight. The dye we use is a custom made organic compound but it could be also naturally derived, for example, from cranberry juice.

Skip to 0 minutes and 48 secondsWhen photons reach the dye molecules - the photon excites an electron to a higher energy level. These high energy electrons are then injected into the TIO2 semiconductor particles - leaving behind a positively charged dye molecule, a hole. The electron once separated from the dye molecule can freely diffuse inside a network of TIO2 particles eventually reaching a negative electrode of the solar cell. This electrode is made of a conductive transparent glass providing a high voltage terminal of the solar cell. The energy of these electrons connected to an external electrical network is converted to electrical work.

Skip to 1 minute and 30 secondsTo close the circuit the electrons are fed to the solar cell through a second electrode providing the positive terminal or the solar cell. This electrode is coated with a catalyst such as a platinum metal or a graphite transfer of an electron from the iodide to the positively charged dye molecule restores the neutral state of the dye molecules.

Skip to 1 minute and 55 secondsThe above cycle is repeated infinitely as long as light is shining on the solar cell and the components remain chemically stable and the layers are well connected to each other. A dye-sensitised solar cell through various temporary chemical changes was able to convert photons into electrons it nearly hundred percent quantum efficiency. That's three main steps of light harvesting, charge separation and charge collection are actually common to all solar technology is being developed. The main differences between the various technologies are the choice of semiconductor materials used in the device architectures.

Dye-sensitised solar cells

The video above shows how we can convert solar energy into electrical energy using a dye-sensitised solar cell.

Dye-sensitised solar cells

Dye-sensitised solar cells (DSSC) are a relatively new and low-cost type of photovoltaic devices. They can convert solar photons to electrons with close to 100 % efficiency, at the peak absorption wavelength, although their overall efficiencies are still significantly lower than the silicon cells you may have on your house today.

Dye-sensitised solar cells have the benefits of being low cost to manufacture, can be made using earth abundant materials - even be assembled using materials found in a typical household - and can be made on flexible substrates.

While this type of solar cell is not yet efficient enough to be deployed at a large scale, it is hoped that continued research and development will make this happen in the future.

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How to Survive on Earth: Energy Materials for a Sustainable Future

University of Wollongong

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