Solar Future

It is predicted that in near future solar cells will be everywhere and it is possible that they might not be visible. They might be either transparent, integrated into your windows, embedded within your phone screen and it only possible with solar cells that can be easily manufactured and are feasible enough to integrate with existing and non-existing technologies. 

Till today solar cells have an efficiency of 15 – 20% at its peak conditions. Lifetimes of these of these are increasing from average lifetime up to 15 years. However after extensive research and development solar cells made of organic matter like polymers, photosensitive dye or organic small molecule technology while promising cheap and portable solar power. They will be much simpler to manufacture at low prices making them quite affordable for low profile consumers.

SOLAR CELL BACKGROUND

The composition of solar cells can be of three different sources including dye, polymer or small molecule organic semiconductors. The most efficient cell today is made from dye mostly known as Gratzel cell. These cells have very simple structure consisting of two electrodes and an iodide containing electrolyte. Both of these electrodes are made using common and non-toxic material. When lights falls on the dye sensitized solar cell it is absorbed by the dye. The electrons that are excited, due to extra energy can escape from the dye into the TiO₂ and diffuse through the TiO₂ to the electrode. These electrons are then returned to the dye through electrolyte. This process is quite similar to photosynthesis, because dye, like chlorophyll in plants, is not involved in charge transport. 

In polymer cells, the conjugated polymer acts as the electron donor with another material such as fullerene acting as an electron acceptor. With right combination of polymer and acceptor, blend with organic solvents can be done easily and then either printed or spin coated. However there are many challenges that are still needed to be addressed including absorption range, photon-electron conversion rate and carrier mobility.

The small molecule system works exactly in the same manner except the small molecules called oligomers acts as photon absorbers. Unlike polymer technology this material is layered using vacuum deposition.

One of the factor achieving efficient solar is the material’s electron mobility. The electron mobility of polymers is low in comparison with dye-sensitized materials however they do have an advantage of being solid over dye-sensitized material, as they require liquid electrolyte, which is quite difficult to handle.  The productivity of polymer cells may catch up one day but that time dye sensitized cells can reach higher efficiency than polymers.

Following video explains method of making domestic solar (Gratzel) cells