Solar cell paint developed

Suppose if the next coat of paint you put on the outside of your home generates electricity from light -- electricity that can be used to power the appliances and equipment on the inside.

A team of researchers at the University of Notre Dame has made a major advance toward this vision by creating an inexpensive material that uses semiconducting nanoparticles to produce energy.

By incorporating power-producing nanoparticles, called quantum dots, into a spreadable compound, a one-coat solar paint was produced that can be applied to any conductive surface without special equipment.

The team's search for the new material, described in the journal ACS Nano, centered on nano-sized particles of titanium dioxide, which were coated with either cadmium sulfide or cadmium selenide. The particles were then suspended in a water-alcohol mixture to create a paste. When the paste was brushed onto a transparent conducting material and exposed to light, it created electricity.

The best light-to-energy conversion efficiency achieved by this is 1 percent, which is well behind the usual 10 to 15 percent efficiency of commercial silicon solar cells; but this paint can be made cheaply and in large quantities. If efficiency can be improved, it would be worthwhile to use in day-today activities.

Nanomechanical oscillator

Physicists, have shown how a nanomechanical oscillator can be used for detection and amplification of feeble radio waves or microwaves. A measurement using such a tiny device, resembling a miniaturized guitar string, can be performed with the least possible disturbance.

The researchers cooled the nanomechanical oscillator, thousand times thinner than a human hair, down to a low temperature near the absolute zero at -273 centigrade. Under such extreme conditions, even nearly macroscopic sized objects follow the laws of quantum physics which often contradict common sense. In the Low Temperature Laboratory experiments, the nearly billion atoms comprising the nanomechanical resonator were oscillating in pace in their shared quantum state.

The scientists had fabricated the device in contact with a superconducting cavity resonator, which exchanges energy with the nanomechanical resonator. This allowed amplification of their resonant motion. This is very similar to what happens in a guitar, where the string and the echo chamber resonate at the same frequency. Instead of the musician playing the guitar string, the energy source was provided by a microwave laser.

Newest Energy Material: Application in Computer, Lighting Technologies

Arizona State University researchers have created a new compound crystal material that promises to help produce advances in a range of scientific and technological pursuits.

The newest material, called erbium chloride silicate, can be used to develop the next generations of computers, improve the capabilities of the internet, increase the efficiency of silicon-based photovoltaic cells to convert sunlight into electrical energy, and enhance the quality of solid-state lighting and sensor technology.

Ning's research team of team of students and post-doctoral degree assistants help synthesize the new compound in ASU's Nanophotonics Lab in the School of Electrical, Computer and Energy Engineering, one of the university's Ira A. Fulton Schools of Engineering.

The breakthrough involves the first-ever synthesis of a new erbium compound in the form of a single-crystal nanowire, which has superior properties compared to erbium compounds in other forms.

Erbium is one of the most important members of the rare earth family in the periodic table of chemical elements. It emits photons in the wavelength range of 1.5 micrometers, which are used in the optical fibers essential to high-quality performance of the Internet and telephones.

Erbium is used in doping optical fibers to amplify the signal of the internet and telephones in telecommunications systems. Doping is the term used to describe the process of inserting low concentrations of various elements into other substances as a way to alter the electrical or optical properties of the substances to produce desired results. The elements used in such processes are referred to as dopants.

With the new erbium compound, 1,000 times more erbium atoms are contained in the compound. This means many devices can be integrated into a chip-scale system. Thus the new compound materials containing erbium can be integrated with silicon to combine computing and communication functionalities on the same inexpensive silicon platform to increase the speed of computing and internet operation at the same time. Erbium materials can also be used to increase the energy-conversion efficiency of silicon solar cells.

Silicon does not absorb solar radiation with wavelengths longer than 1.1 microns, which results in waste of energy -- making solar cells less efficient. Erbium materials can remedy the situation by converting two or more photons carrying small amounts of energy into one photon that is carrying a larger amount of energy. The single, more powerful photon can then be absorbed by silicon, thus increasing the efficiency of solar cells.

Erbium materials also help absorb ultraviolet light from the sun and convert it into photons carrying small amounts of energy, which can then be more efficiently converted into electricity by silicon cells. This color-conversion function of turning ultraviolet light into other visible colors of light is also important in generating white light for solid-state lighting devices.

While erbium's importance is well-recognized, producing erbium materials of high quality has been challenging. The standard approach is to introduce erbium as a dopant into various host materials, such as silicon oxide, silicon, and many other crystals and glasses. One big problem has been that we have not been able to enough erbium atoms could not be introduced into crystals and glasses without degrading optical quality, because too many of these kinds of dopants would cluster, which lowers the optical quality.

What is unique about the new erbium material synthesized here is that erbium is no longer randomly introduced as a dopant. Instead, erbium is part of a uniform compound and the number of erbium atoms is a factor of 1,000 more than the maximum amount that can be introduced in other erbium-doped materials. Increasing the number of erbium atoms provides more optical activity to produce stronger lighting. It also enhances the conversion of different colors of light into white light to produce higher-quality solid-state lighting and enables solar cells to more efficiently convert sunlight in electrical energy. In addition, since erbium atoms are organized in a periodic array, they do not cluster in this new compound. The fact that the material has been produced in a high-quality single-crystal form makes the optical quality superior to the other doped materials.

This new erbium compound can be used for various applications, such as increasing silicon solar cell efficiency and making miniaturized optical amplifiers for chip-scale photonic systems for computers and high-speed internet.