Nanorods for solar cells

Commercial solar cells could have double the efficiency in five years' time with novel research into nanomaterials.

The EU-funded project, called ROD-SOL (Rods for Novel Solar Cells), aims to create large-scale methods for growing arrays of small, 3D silicon cylinders known as nanorods. This would replace conventional silicon-growing techniques that involve casting ingots and cutting wafers.

A solar cell based on arrays of 3D nanorods will absorb more photons than regular 2D wafers because it scatters less light, said Juhana Kostamo, managing director of

, an atomic layer deposition (ALD) systems manufacturer based in Finland. The company is one of several industrial partners involved in ROD-SOL. 'Current solar cells in mass production have an efficiency typically ranging from five per cent to 10 per cent. With this technology it is possible to double that efficiency.'

While several companies and research groups have produced working prototypes of solar cells based on silicon nanorods, the technology has yet to be commercialised. One reason is cost. Silicon nanorods are currently grown on silicon wafers, but the ROD-SOL team hopes to optimise a method for growing silicon nanorods on larger, less expensive substrates, such as glass or synthetic foil that could be fashioned into thin-film solar cells. Silicon nanorods are typically grown using a process common in the semiconductor industry known as chemical vapour deposition (CVD). In this process, a substrate is exposed to vapourising compounds that either react or decompose on its surface to produce a deposit. Once the nanorods are grown, they are joined together to form a matrix using atomic layer deposition (ALD).