Avalanche Effect Could Make Solar Cells Highly Efficient

Solar cells have the opportunity to revolutionize the electric energy generation process on Earth, but their use today is highly restricted by the high manufacturing costs and their notorious inefficiency in converting light into electricity. The record conversion efficiency for solar cells has been set a couple of weeks back with a prototype able to turn about 23.2 percent of the gathered light directly into electricity - when the average efficiency of most cells never exceeds 15 percent.

The so-called electron avalanche effect was recently demonstrated for the first time by a team of researchers from TU Delft and FOM Foundation for Fundamental Research on Matter inside a solar cell and promises to create cheaper and more efficient solar cells.

The solar cell prototype created by them involves the use of semiconducting materials made of nanocrystals. Traditional semiconducting materials used to manufacture solar cells generate one electron per absorbed photon. However, in certain semiconductor nanocrystals one photon of light can release two or three electrons, which translates in a maximum conversion efficiency of 44 percent. As it turns out, such solar cells are also significantly cheaper to manufacture than those made through the current production process.

The electron avalanche effect was first found inside solar cells some four years ago at the Los Alamos National Laboratories, albeit the measurements were inconclusive to establish whether or not the effect was real.

The testing rig used by the TU Delft researchers is made out of lead selenide nanocrystals and does indeed seem to present the electron avalanche effect. Joint Solar Programme TU Delft's Professor Laurens Siebbels says that the effect is much smaller than previously expected but the measurements using ultra-fast laser methods prove nonetheless that it is real. Siebbels points out that the research of the TU Delft team would help further efforts into unlocking the secrets behind the electron avalanche effect inside solar cells.