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(Nanowerk News) IMEC has realized a single-junction GaAs solar cell on a Ge substrate with a record conversion efficiency of 24.7%. The efficiency was measured and confirmed by NREL (National Renewable Energy Laboratory, US). GaAs solar cells are used in satellite solar panels and earth-based solar concentrators.
IMEC realized this record on a single-junction GaAs cell, grown epitaxially on a Ge substrate with an improved micro-defect distribution. The record cell measures 0.25cm², and shows an efficiency of 24.7%, with an open-circuit voltage (Voc) of 999 mV, a short-circuit current (Jsc) of 29.7 mA/cm², and a fill factor of 83.2%. The cell was made under the ESA-IMAGER project. Umicore, a leading materials technology group, produced the Ge substrate through an optimized manufacturing technology, aimed at improving the intrinsic germanium crystal quality.
Improving the efficiency of this single-junction GaAs cell is a further step in the development of a hybrid monolithic/mechanically stacked triple-junction solar cell. This type of solar cells consists of stacks of solar cells made of different semiconductors, carefully chosen to absorb the solar spectrum as efficiently as possible. Among the many possible combinations, IMEC focuses on stacked cells consisting of top cells with III-V materials and bottom cells made from Ge. With this combination, IMEC is targeting a conversion efficiency of 35% and more. The resulting stacks can be used in satellites and earth-based concentrators, where high-efficiency energy conversion is paramount.
In contrast to earlier approaches for anode coating, the Northwestern nickel oxide coating is cheap, electrically homogeneous and non-corrosive. In the case of model bulk-heterojunction cells, the Northwestern team has increased the cell voltage by approximately 40 percent and the power conversion efficiency from approximately 3 to 4 percent to 5.2 to 5.6 percent.
The researchers currently are working on further tuning the anode coating technique for increased hole extraction and electron blocking efficiency and moving to production-scaling experiments on flexible substrates.
Graphene--a flat single layer of carbon atoms--can transport electrons at remarkable speeds, making it a promising material for electronic devices. Until recently, researchers had been able to make only small flakes of the material, and only in small quantities. However, Rutgers University researchers have developed an easy way to make transparent graphene films that are a few centimeters wide and one to five nanometers thick.
Thin films of graphene could provide a cheap replacement for the transparent, conductive indium tin oxide electrodes used in organic solar cells. They could also replace the silicon thin-film transistors common in display screens. Graphene can transport electrons tens of times faster than silicon, so graphene-based transistors could work faster and consume less power.
The potential of plug-in hybrids and electric vehicles to curb petroleum use has grabbed a lot of attention lately. But there is still a big obstacle to clear before such cars can become the dominant vehicles on the road: automakers will need to find an efficient way to supply them with heat and air conditioning. That's because conventional heating and cooling systems either don't work or are inefficient in such vehicles, significantly lowering their range in hot and cold weather.
One of the leading candidates for an alternative system is based on thermoelectrics, semiconductor devices that can provide either heat or cooling, depending on the direction the electric current is flowing. Major automakers, such as GM and Ford, are now developing systems based on existing thermoelectric semiconductors, and experimental materials that use nanotechnology promise to make such systems even more appealing.
Originally posted by Voxel
This entire thread is off topic. It starts with an article about impractical thermoelectric materials and then every other post afterwards deals with the topic of solar panels.
Converting heat into electricity is not new. Most of NASA's remote controlled rovers have some sort of nuclear battery on them. A nuclear batter is nothing but a sandwich of some radioisotope (making heat) and thermoelectric materials.
Now some common sense. Most of the uses of thermoelectric material posited by people in this thread will never work.
Thermoelectric materials work because there is a strong temperature gradient present in the material. Most of the uses cited in this thread attempt to take waste heat from something that is doing work and returning the waste heat as electricity to help it do said work.
The problem with this is easy to see in the computer example. Computers have fans and heat sinks on their hot components to keep them within a usable temperature range. The whole purpose of those heat sinks is to pull the heat away from the chips and transmit it to the air.
This goes against the very nature of thermoelectric materials which would require you to keep the heat on one side and NOT transmit it to the other side. They say in the article that the challenge is finding a good electrical conductor that is a poor thermal conductor. Put a poor thermal conductor on top of a computer chip and watch what happens.
So you could not use thermoelectric materials to make use of waste heat from a processor, or a motor, or even a gas-burning engine with any efficiency because all of those things need to be actively cooled and not encased in a thermal insulator.
Finally, the idea that you can power a house off the temperature gradient present between hot-air and air-conditioned-air is completely bonkers. You are using massive amounts of energy to cool the air in the first place and will only get a few watts per hour out of it.
Solar panels just make sense. Provided we can make them cheaply. Not cheap as in end-user cost but cheap in resources and energy requirements for manufacture. It doesn't really matter if a roof full of solar panels could provide for all the energy requirements of a home if the factory making them consumes 100kw/h in the manufacture of one sq. ft. of panel.
Sunrgi estimates that its system will be capable of producing electricity at a wholesale cost of five cents per kilowatt-hour. Prototypes have been built and tested both in the laboratory and in the field, and the company expects to start commercial production in 12 to 15 months. "It's quite an aggressive claim," says Daniel Friedman, a solar-energy researcher at the U.S. National Renewable Energy Laboratory (NREL). He says that most others in the space are still working toward seven or eight cents per kilowatt-hour. "I can't say Sunrgi won't achieve what it's claiming, but right now, it's just on paper, and costs like that are only going to be a reality at the large manufacturing level," he says. "Even then, the five-cent figure sounds really optimistic."
In conventional solar cells, one photon (light particle) can release precisely one electron. The creation of these free electrons ensures that the solar cell works and can provide power. The more electrons released, the higher the output of the solar cell.
In some semiconducting nanocrystals, however, one photon can release two or three electrons, hence the term avalanche effect. This could theoretically lead to a maximum output of 44 percent in a solar cell comprising the correct semiconducting nanocrystals. Moreover, these solar cells can be manufactured relatively cheaply.
Researchers are working on a thermoelectric generator that converts the heat from car exhaust fumes into electricity. The module feeds the energy into the car’s electronic systems. This cuts fuel consumption and helps reduce the CO2 emissions from motor vehicles.
Posted by Martin Roscheisen, CEO
As we are busy ramping our operation, we almost forgot to recognize achieving a major milestone in solar technology: The solar industry's first 1GW production tool.
Nanosolar Achieves 1GW CIGS Deposition Throughput
San Jose, CA | Posted on June 18th, 2008
Most production tools in the solar industry tend to have 10-30MW in annual production capacity. How is it possible to have a single tool with Gigawatt throughput?
This feat is fundamentally enabled through the proprietary nanoparticle ink we have invested so many years developing. It allows us to deliver efficient solar cells (presently up to more than 14%) that are simply printed.
Printing is a simple, fast, and robust coating process that in particular eliminates the need for expensive high-vacuum chambers and the kinds of high-vacuum based deposition techniques from industries where there's a lot more $/sqm available for competitive manufacturing cost.
Our 1GW CIGS coater cost $1.65 million. At the 100 feet-per-minute speed shown in the video, that's an astonishing two orders of magnitude more capital efficient than a high-vacuum process: a twenty times slower high-vacuum tool would have cost about ten times as much per tool.
Plus if we cared to run it even faster, we could. (The same coating technique works in principle for speeds up to 2000 feet-per-minute too. In fact, it turns out the faster we run, the better the coating!)