American institute of physics displays us more efficient Selenium solar cells

Did you know that many researchers would like to find light-catching materials in order to convert more of the sun’s energy into carbon-free electric power?

A new analysis announced in the magazine Applied Physics Letters in August 2010 (published by the American Institute of Physics), explains how solar power could potentially be collected by using oxide materials that have the element selenium. A team at the Lawrence Berkeley National Laboratory in Berkeley, California, inserted selenium in zinc oxide, a relatively economical material that could make more efficient use of the sun’s energy.


The team noticed that even a relatively small level of selenium, just nine per cent of the mostly zinc-oxide base, drastically boosted the material’s performance in absorbing light.

The most important author of this analysis, Marie Mayer (a fourth-year University of California, Berkeley doctoral student) states that photo-electrochemical water splitting, that signifies employing energy from the sun to cleave water into hydrogen and oxygen gases, could possibly be the most interesting future application for her work. Using this reaction is key to the eventual production of zero-emission hydrogen powered automobiles, which hypothetically will run only on water and sunlight.

The conversion effectiveness of a PV cell is the amount of sunlight energy that the solar cell converts to electric power. This is very important when discussing photovoltaic units, because boosting this efficiency is vital to making photovoltaic energy competitive with more traditional sources of energy (e.g., classic fuels).

For comparison, the very first photovoltaic units converted about 1%-2% of sunlight energy into electrical energy. Today’s photovoltaic devices convert 7%-17% of light energy into electric energy. Of course, the other side of the equation is the dollars it costs to produce the PV devices. This has been enhanced over the decades as well. In fact, today’s PV systems make electricity at a fraction of the cost of first PV systems.

In the 1990s, when silicon cells were 2 times as thick, efficiencies were much lower than these days and lifetimes were reduced, it may well have cost more energy to produce a cell than it could generate in a lifetime. In the meantime, the technology has progressed considerably, and the energy payback time (defined as the recovery time needed for generating the energy spent to make the respective technical energy systems) of a modern photovoltaic module is typically from 1 to 4 years depending on the module type and location.

Commonly, thin-film technologies – despite having reasonably low conversion efficiencies – achieve substantially shorter energy payback times than conventional systems (often < 1 year). With a common lifetime of 20 to 30 years, this means that contemporary solar cells are net energy producers, i.e. they generate significantly more energy over their lifetime than the energy expended in producing them.

Rosalind Sanders

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