[amor de cosmos]

Nanostructures improve the efficiency of solar cells
25 April 2013

Researchers have been able to improve the efficiency of solar cells by coating the cell surface with extremely small nanoscale structures. The new technology has been shown to nearly eliminate the reflection losses of solar radiation. Cost-effective solar photovoltaic materials are being developed within the Academy of Finland’s research programme Photonics and Modern Imaging Techniques.

The nanostructured black silicon coating features very low reflectivity, meaning that a larger portion of the Sun’s radiation can be exploited. At Aalto University, a research team led by Assistant Professor Hele Savin is conducting studies on crystalline silicon solar cells, which are the main type of solar cells that are currently on the market.

“The advantages of silicon include the long-term stability, sufficiency, low cost and non-toxicity of the element, as well as the advanced production technology. Another benefit of these solar cells is their relatively high efficiency and technological compatibility with the manufacturing technologies currently used by the semiconductor industry,” Savin explains. The technology, however, still calls for development and improvement.

http://www.aka.fi/en-GB/A/Academy-of...f-solar-cells/

Sharp Achieves 37.9% Solar Cell Conversion Efficiency
26 APRIL 2013

Sharp Corporation has achieved solar cell conversion efficiency*1 of 37.9%*2 using a triple-junction compound solar cell in which three photo-absorption layers are stacked together.

Sharp achieved this latest breakthrough as a result of a research and development initiative promoted by Japan’s New Energy and Industrial Technology Development Organization (NEDO)*3 on the theme of "R&D on Innovative Solar Cells." Measurement of the value of 37.9%, which sets a new record for the world's highest conversion efficiency, was confirmed at the National Institute of Advanced Industrial Science and Technology (AIST).

Compound solar cells utilize photo-absorption layers made from compounds consisting of two or more elements, such as indium and gallium. The basic structure of this latest triple-junction compound solar cell uses proprietary Sharp technology that enables efficient stacking of the three photo-absorption layers, with InGaAs (indium gallium arsenide) as the bottom layer.

By optimizing the relative proportions of indium, gallium, and arsenide, Sharp succeeded in increasing the efficiency with which the cell absorbs sunlight at its various wavelengths. This improvement enabled Sharp to achieve solar cell conversion efficiency*1 of 37.9%*2.

http://www.solarnovus.com/index.php?...rticle&id=6492

Pentacene Coating Could Push Solar Cell Efficiency Beyond Shockley-Queisser Limit
WRITTEN BY SANDRA HENDERSON | 24 APRIL 2013

Thanks to a new coating developed at the Massachusetts Institute of Technology (MIT), solar cells could produce two electrons for every particle of light harvested at the green and blue wavelengths. The research advance could be the key to solar cell efficiencies beyond the Shockley-Queisser limit, which proposes that the ultimate conversion efficiency can never exceed 34% for a single optimised semiconductor junction.

The MIT researchers use the organic molecule pentacene to demonstrate singlet exciton fission, where two electrons are produced for each photon, instead of one. “The physics of what happens to an excited electron — or exciton — in this molecule is different from that of a typical semiconductor such as silicon,” says MIT engineering graduate student Nicholas J. Thompson, who is also a first author of the paper “External Quantum Efficiency Above 100% in a Singlet-Exciton-Fission-Based Organic Photovoltaic Cell,” published in Science. Typically, when a blue or green photon is absorbed and an electron is exited, much of its energy is lost in form of heat. “In our singlet fission device, the excited electron transfers some of its energy to another electron, both of which can be collected as current,” Thompson explains. “This process loses significantly less energy to heat, allowing for more sunlight to be captured and a more efficient cell.”

http://www.solarnovus.com/index.php?...rticle&id=6486