Avalanche Effect Photons on Small Semi Conductor Crystals

In 2004 when the Los Alamos National Laboratory first measured an unusual effect of a photon impacting a silicon solar cell and releasing more than one electron the effect has been a item of great basic research curiosity. Normally a photon coming into a cell will cut loose an electron, and over a complete solar cell, the common efficiency is ranging about 15% with the best nearing 20% and many still lower. In theory, the effect known as the “avalanche effect” would about triple solar cell output to 44%, which would change the economics dramatically.

Then the press release from TU Delft and the FOM Foundation for Fundamental Research on Matter says they have found irrefutable proof that the avalanche effect occurs in specific and very small semi conducting crystals. This confirms the original measurements by Los Alamos and sets up the repeatability testing to come. The publishing of their paper is to be published in the scientific journal Nano Letters this week.

The avalanche effect might show a way to much higher solar cell output and might be a path to lower costs. The current state of engineering has solar voltaic cells quite costly with long time periods for cost recovery. This situation and the low efficiencies handicap the solar voltaic industry.

An improvement may come with nano sized crystals rather than the larger silicon cell design of today. You’ll note in the release that the researchers have substituted lead selenide nano crystals, and that the effect is lower than anticipated. Yet the confirmation of the Los Alamos work is at hand, which should clear up the debate as to the existence of the effect.

TU Delft Professor Laurens Siebbles who ran the tests and authors the paper asserts that his results are the most reliable to date thanks to careful and more detailed measurement using ultra fast laser methods. Siebbles thinks that this research can pave the way to further research that can unravel the secrets of the effect.

This development and the layering techniques using ever increasing segments of the available wavelengths to energize solar voltaic cells bodes well for the future. This press release and the paper offer another path to higher efficiencies in solar voltaic and one can expect improvements in the combined technologies on a single installation in the future. I suspect it will be sooner than one might think, the opportunity to provide some part of one’s electrical needs and add to the overall available energy supply is a strong incentive for saving money.


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