Chinese OPV achieves 10% efficiency

Dan Rogers - 26 Aug 2009

A new organic dye developed in China could compete with conventional solar cell technology.

In tests at the Chinese Academy of Sciences, the metal-free, organic dye almost reached 10% efficiency at converting light into electricity - the level required to be competitive in PV applications.

Dye-sensitised solar cells are considered to be a cheaper alternative to silicon cells and can be printed on flexible substrates for potential applications in building-integrated PVs (BIPVs) and additional power sources for consumer electronics.

Peng Wang, the chemistry professor at the academy who led the research, explains the benefits of the organic dye:
'Considering the limited global ruthenium resource, metal-free organic dyes with a high molar extinction coefficient have attracted considerable attention in recent years.

'In addition, the cost of purification of our metal-free donor-conjugated linker-acceptor (D-p-A) organic dye is much lower than that for ruthenium dyes.'

Organic dyes

The research team developed an organic dye molecule that increased the cell's efficiency by pushing electrons to the semiconductor particles more quickly and stopping electrons and holes from recombining in the cell. The molecule also means that cells absorb more red light than previous technologies.

Peng adds: 'I developed new dyes, one of the key components in dye-sensitised solar cells and combined with other state-of-the-art materials, for cell fabrication and testing the performance of new materials.'

The team also replaced the use of a volatile acetonitrile electrolyte - toxic materials that can evaporate and leak in high temperatures - which are typically used in dye-sensitised solar cells.

This reduced efficiency to 8.1%, but Peng argues that this remains 'impressive' and makes for 'a practical cell.'

'The next step of boosting efficiency will rely mainly on extending the spectral response of sensitisers to the infrared,' adds Peng. 'This should be possible in the coming years.'
'We are now doing some systematic work on the design, synthesis and optoelectronic characterisation of metal-free organic dyes, with a hope to boost the performance of dye-sensitised solar cells,' Peng comments.

Another area of development is in making the dyes suitable for commercial levels of production.

'We are now working on mild synthetic routes to make the large-scale production of this new dye applicable,' he adds.