Power/Performance Bits: March 11

Multiferroic materials
In an advance aimed at making future electronic devices far more energy-efficient than current technologies, researchers from the UCLA Henry Samueli School of Engineering and Applied Science have made major improvements in computer processing using an emerging class of magnetic materials called multiferroics.

The team used multiferroic magnetic materials to reduce the amount of power consumed by logic devices, which can be switched on or off by applying alternating voltage. It then carries power through the material in a cascading wave through the spins of electrons, a process referred to as a spin wave bus.

A spin wave can be thought of as similar to an ocean wave, which keeps water molecules in essentially the same place while the energy is carried through the water, as opposed to an electric current, which can be envisioned as water flowing through a pipe, the researchers explained. Spin waves open an opportunity to realize fundamentally new ways of computing while solving some of the key challenges faced by scaling of conventional semiconductor technology, potentially creating a new paradigm of spin-based electronics.

The UCLA researchers were able to demonstrate that using this multiferroic material to generate spin waves could reduce wasted heat and therefore increase power efficiency for processing by up to 1,000 times.

A picture of spin wave devices, showing magneto-electric cells used for voltage-controlled spin wave generation in the spin wave bus material (yellow stripe). The yellow stripe is about four micrometers in diameter. (Source: UCLA)

Electrical control of magnetism without involving charge currents is a fast-growing area of interest in magnetics research, as it can have major implications for future information processing and data-storage devices.

Fusing energy and beauty
Colorful, see-through solar cells invented at the University of Michigan could one day be used to make stained-glass windows, decorations and even shades that turn the sun’s energy into electricity.

The cells are believed to be the first semi-transparent, colored photovoltaics, and have the potential to vastly broaden the use of the energy source, the researchers said, and offer a very different way of utilizing solar technology rather than concentrating it in a small area. Comparatively, today’s solar panels are black and placed on rooftops of buildings.

The researchers think they can make solar panels more beautiful—any color a designer wants to be deployed even indoors.

The researchers envision them on the sides of buildings, as energy-harvesting billboards and as window shades—a thin layer on homes and cities. Such an approach could be especially attractive in densely populated cities.

Below, in a palm-sized American flag slide, the team demonstrated the technology.

(Source: University of Michigan)

All the red stripes, the blue background and so on are working solar cells.

The Stars and Stripes achieved 2% efficiency. A meter-square panel could generate enough electricity to power fluorescent light bulbs and small electronic gadgets, whereas state-of-the art organic cells in research labs are roughly 10% efficient.

The researchers are working to improve their numbers with new materials, but there will always be a tradeoff between beauty and utility in this case. Traditional black solar cells absorb all wavelengths of visible light but these are designed to transmit, or—in other versions—reflect certain colors, so by nature they’re kicking energy from those wavelengths back out to our eyes rather than converting it to electricity.

Unlike other color solar cells, these don’t rely on dyes or microstructures that can blur the image behind them: the cells are mechanically structured to transmit certain light wavelengths. To get different colors, the researchers varied the thickness of the semiconductor layer of amorphous silicon in the cells. The blue regions are six nanometers thick while the red is 31 (the team also made green, but that color isn’t in the flag).