Synthetic chlorophyll shows promise for solar cells

Researchers at Massey University’s Nanomaterials Research Centre (NRC) in New Zealand have developed a range of coloured dyes for use in dye-sensitised organic solar cells. The work is at an early stage, but the aim is to generate electricity at a tenth of the cost of current silicon-based cells.

Massey chemist Wayne Campbell’s research follows on from 10 years’ work led by former NRC Director David Officer. Campbell’s group is also collaborating closely with that of Michael Grätzel, a photonics expert at the École Polytechnique Fédérale de Lausanne in Switzerland.

Porphyrin-based demonstration photovoltaic cell (© Wayne Campbell, Massey University)

Campbell’s synthetic dyes are made from simple organic compounds closely related to those found in nature. One particular green dye is a form of synthetic chlorophyll derived from the light-harvesting porphyrin pigments plants use for photosynthesis.

Like other types of organic photovoltaics, the demonstration cells developed at the NRC are well-suited to generating electricity in low-light conditions. The photosynthesising dyes could be incorporated into tinted windows, roofing materials and walls, and Campbell’s group has received expressions of interest from New Zealand companies.

‘There are still many obstacles to be overcome in cell construction,’ says Campbell. ‘We are currently not at the stage of commercialisation, and are primarily involved in the design and synthesis of the dye. The solar cell technology that uses the dye, known as the Grätzel Cell, is currently well developed, and a number of companies already have commercial licenses to produce these cells (e.g., Dyesol and Konarka).’

Campbell claims that the green solar cells are more environmentally friendly than silicon-based photovoltaics as they are made from titanium dioxide – a non-toxic white mineral in plentiful supply in New Zealand’s black sand. Titanium dioxide is already widely used in consumer products such as toothpaste, white paints and cosmetics.

A proof-of-concept cell has been developed by Dyesol using one of the green dyes, and Campbell and his colleagues are currently gathering data on cell lifetimes.

Figure: Porphyrin-based demonstration photovoltaic cell (© Wayne Campbell, Massey University).

Further reading: Porphyrins as light harvesters in the dye-sensitised TiO2 solar cell, Campbell et al., Coordination Chemistry Reviews 248, 1363 (2004) (subscription required).

Article first published in Nanomaterials News.