Bendy solar cells that can be printed onto paper

Imagine decorating your bedroom walls with paper made from the same solar cells that now power your home.

That's the tantalising possibility thrown up by the development of lightweight solar cells that can be printed on paper, be scrunched up like an accordion and still conduct electricity. Researchers at the Massachusetts Institute of Technology printed them on untreated copy paper using a technique that could help slash the cost of producing solar cells.

The glass or plastic backing typically used for solar cells accounts for 25 to 60 per cent of the total cost for materials and so lightweight paper-based cells could significantly reduce photovoltaic production, transportation and installation costs.

A team led by Vladimir Bulović and Karen Gleason changed an ingredient in the material sandwich that makes up a solar cell. They used a flexible conducting polymer as the bottom electrode in the sandwich instead of a transparent metal oxide.

The researchers constructed the solar cell using a dry fabrication process, depositing each layer as a vapour dispersed in a vacuum. A thin mask patterned with holes restricted the placement of the five separate layers of material into cells: the polymer electrode, three energy-collecting materials and the metal electrode at the top of the sandwich. The fact that the vapour was deposited at a relatively low temperature means that the technique allows solar cells to be created on fabric, plastic, tissue paper and even printed newspaper.

At the moment, these paper solar cells are only about 1 per cent efficient. But that's still enough to run small electronics like an alarm clock. A lightweight solar cell could be used for wallpaper or window shades and simply installed using staples or glue.
ture of other compounds. The average temperature is – 235°C. It is 38.87 times bigger and 17.132 times more massive than the Earth.

The First Real Brain-Like Computer Could be Made of the Same Material That Makes DVDs

Scientists in the UK and in California may have found a holy grail of brain-like computing--a material that can both simulate the behavior of neurons and run on very low power--in an abundant and familiar medium. The very same phase-changing material that allows us to record on DVDs could be used to build a low-power brain-like processor capable of learning and adapting without the need for extensive pre-programming.

The material is GST--so named for the materials it contains (germanium, antimony, and tellurium--and it possesses just the kind of phase-changing properties that researchers are looking for. Phase-change alloys like GST can exist in various phases, ranging from crystalline, ordered structures to chaotic, amorphous structures. Their states depends on various external factors, like heat or charge.

In DVDs, GST allows discs to be embedded with binary ones and zeros that can later be read by a laser. That’s fine for film screening purposes, but GST can actually exist in various degrees of phase change between completely crystalline and completely amorphous, and thus it can store information across a wider range of values--just like a neuron, which fires only when a build-up of incoming signals reaches a certain threshold.

The GST neurons/synapses developed by the University of Exeter and Stanford team also can adjust the strength of the synapses between them--a key characteristic of inter-neuron communication--because of its inherent ability to modify its electrical resistance. This allows the GST neurons to adjust the strength of the connections between them to signify the importance of incoming signals and prioritize signals flowing through a neural network.

All said, those two qualities--the ability to store information across a range of phase states, and a low-power, adjustable-strength synapse--make for a pretty nice electronic analog for a working brain. But the work is very preliminary, and it’s one thing to have a few working synthetic neurons in the lab, and quite another to have a working network of thousands or millions (much less hundreds of millions).

In other words, it’s pretty amazing that DVD tech can do these things, but a proper brain-like computer is still many years and several breakthroughs distant