UCLA makes 11.5 percent efficient triple-junction organic PV cell

Materials scientists at the University of California, Los Angeles (UCLA) have produced a demonstrator of an organic solar cell that converts 11.5% of light into electricity.

Triple tandem
The new photovoltaic unit has a triple-junction tandem design. This was inspired by the multi-junction solar cells based on III-V semiconductors used to power satellites. Details of the new device, which currently measures only 1cm2, were given in a paper published in the journal Advanced Materials on 14 July.

The cell is made of three separate optimised polymer bandgaps sandwiched between layers of zinc oxide, Pedot:PSS, and tungsten oxide.

Once the triple-junction cell can be scaled up, the developers believe it will be able to compete with existing inorganic photovoltaics in high performance applications. Major challenges to doing this involve improving processing compatibility, allowing each layer to be constructed using solution processing, and the design of the interfacial layer.

Scale-up savings
UCLA Researcher Johnny Chen notes that the project benefited from encapsulation technology originally developed for OLED consumer devices by Sumitomo Chemical.

The potential for printing tandem organic solar cells at low-cost has already been demonstrated this year. In June, a team from the Technical University of Denmark produced a double-layer tandem cell in a roll to roll process - though it had a much lower energy conversion rate.