Engineers Double Efficiency of Solar Film Cells


nanomanufacturing-6Engineers and materials scientists at University of California in Los Angeles improved the design of solar cells built in a thin semi-transparent film that nearly doubles their ability to generate power. A team from the lab of engineering professor Yang Yang described its findings online in Friday’s issue of the journal Energy and Environmental Science (free registration required).

Yang’s lab developed an earlier form of the solar cell with a near-infrared light-sensitive polymer. The cell produces energy by absorbing mainly infrared light, not visible light. The cell developed in that first round was 70 percent transparent, and achieved a power-generating efficiency of 4 percent.

The new version of the solar cell from Yang’s lab is a tandem device with two thin light-activated polymer solar cells that absorb more light than the single-cell version. The new device also combines transparent and semi-transparent polymer cells, and a layer between the two cells to reduce energy loss.

Tests conducted by Yang’s team show the tandem device achieves a conversion rate — percentage of energy from the sun converted to electric power — of 7.3 percent, compared to 4 percent in the earlier version. The new device captures up to 80 percent of infrared light, with a small amount of light from the visible spectrum, compared to about 40 percent of infrared light absorbed in the earlier single-cell version.

The process to generate the solar cells, say the researchers, uses low temperatures, which makes production of the cells more feasible. The cells can also be produced to appear in various shades of light gray, green, or brown to blend in with building exteriors, windows, or electronic surfaces.

“We anticipate this device,” says Yang, “will offer new directions for solar cells, including the creation of solar windows on homes and office buildings.”

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New 2-D Material for Next Generation High-Speed Electronics


QDOTS imagesCAKXSY1K 8Jan. 21, 2013 — Scientists at CSIRO and RMIT University have produced a new two-dimensional material that could revolutionise the electronics market, making “nano” more than just a marketing term.

 

 

The material — made up of layers of crystal known as molybdenum oxides — has unique properties that encourage the free flow of electrons at ultra-high speeds.

In a paper published in the January issue of materials science journal Advanced Materials, the researchers explain how they adapted a revolutionary material known as graphene to create a new conductive nano-material.

Graphene was created in 2004 by scientists in the UK and won its inventors a Nobel Prize in 2010. While graphene supports high speed electrons, its physical properties prevent it from being used for high-speed electronics.

The CSIRO’s Dr Serge Zhuiykov said the new nano-material was made up of layered sheets — similar to graphite layers that make up a pencil’s core.

“Within these layers, electrons are able to zip through at high speeds with minimal scattering,” Dr Zhuiykov said.

“The importance of our breakthrough is how quickly and fluently electrons — which conduct electricity — are able to flow through the new material.”

RMIT’s Professor Kourosh Kalantar-zadeh said the researchers were able to remove “road blocks” that could obstruct the electrons, an essential step for the development of high-speed electronics.

“Instead of scattering when they hit road blocks, as they would in conventional materials, they can simply pass through this new material and get through the structure faster,” Professor Kalantar-zadeh said.

“Quite simply, if electrons can pass through a structure quicker, we can build devices that are smaller and transfer data at much higher speeds.

“While more work needs to be done before we can develop actual gadgets using this new 2D nano-material, this breakthrough lays the foundation for a new electronics revolution and we look forward to exploring its potential.”

In the paper titled ‘Enhanced Charge Carrier Mobility in Two-Dimensional High Dielectric Molybdenum Oxide,’ the researchers describe how they used a process known as “exfoliation” to create layers of the material ~11 nm thick.

The material was manipulated to convert it into a semiconductor and nanoscale transistors were then created using molybdenum oxide.

The result was electron mobility values of >1,100 cm2/Vs — exceeding the current industry standard for low dimensional silicon.

The work, with RMIT doctoral researcher Sivacarendran Balendhran as the lead author, was supported by the CSIRO Sensors and Sensor Networks Transformational Capability Platform and the CSIRO Materials Science and Engineering Division.

It was also a result of collaboration between researchers from Monash University, University of California — Los Angeles (UCLA), CSIRO, Massachusetts Institute of Technology (MIT) and RMIT.