Image caption Gratzel cells mimic natural plant photosynthesis

The inventor of a low-cost solar cell that could be used to build electricity generating windows has been awarded this year's Millennium Technology Prize.

Professor Michael Gratzel of the Lausanne Federal Technology Institute received the €800,000 (£660,000) prize at a ceremony in Helsinki.

Professor Gratzel's innovation mimics the way plants turn light into energy.

Two British inventors also won prizes of €150,000 (£124,000) each.

The three shortlisted entries were all vying for the world's biggest technology prize, which is awarded every other year by Finland's Technology Academy.

Big honour

Professor Gratzel expressed his excitement to BBC News: "It was a wonderful experience to win the grand prix, and of course a tremendous honour".

"The constraint of solar energy has traditionally been its price. 'Gratzel cells' provide a more affordable way of harnessing solar energy," said Dr Ainomaija Haarla, President of Technology Academy Finland.

"Gratzel's innovation is likely to have an important role in low-cost, large-scale solutions for renewable energy."

You could think that the glass of all high-rises in New York would be electricity generating panels Professor Michael Gratzel, Millennium Technology Prize winner

Explaining his inspiration, he said: "I was always intrigued by the way plants capture sunlight and turn it into fuels like sugar.

"Natural photosynthesis was the inspiration, and our solar cell is the only one that mimics the natural photosynthetic process."

Gratzel cells rely on nanotechnology to produce power from sunlight. "We are using nanocrystal films in which the particles are so small, they don't scatter light," said Professor Gratzel.

"You can imagine using those cells as electricity producing windows.

"What's very exciting is that you collect light from all sides, so can capture electricity from the inside as well as the outside.

"You could think that the glass of all high-rises in New York would be electricity generating panels," he said.

Gratzel cells have recently been launched in consumer products, including as battery charging backpacks, and Professor Gratzel said that the €800,000 prize would benefit his research and go back into science.

The shortlist

Both the other shortlisted nominations for the prize were British inventors, each of whom won €150,000.

Professor Sir Richard Friend of the University of Cambridge invented organic Light Emitting Diodes, which Finland's Technology Academy said was "a crucial milestone in plastic electronics".

"Electronic paper, cheap organic solar cells and illuminating wall paper are examples of the revolutionary future products his work has made possible," it said.

And Professor Stephen Furber of Manchester University is the principal designer of the ARM 32-bit RISC microprocessor, an innovation found in gadgets ranging from Apple's iPhone to Microsoft's Zune. The Academy said it "revolutionised mobile electronics".

It said: "The ingeniously designed processor enabled the development of cheap, powerful handheld, battery-operated devices".

Previous winners of the prize have included Sir Tim Berners-Lee, who is widely credited as having invented the web, and Professor Shuji Nakamura, who invented blue and white Light Emitting Diodes.