The research team has developed a new strategy for making and attaching colored materials to the surface of titanium dioxide nanoparticles and have also shown for the first time that simple compounds of the readily available metal zinc may be used.

Dye-sensitized solar cells (DSCs) consist of a semiconductor, titanium dioxide, which is coated with a colored dye. The dye absorbs sunlight and injects an electron into the semiconductor. This is the primary event leading to the photocurrent.

Project Officer Dr Biljana Bozic for University of Basel’s research group said that the key discovery was finding a method for the simultaneous synthesis of the dye and its attachment to the semiconductor surface.  Researchers Nik Hostettler and Ewald Schoenhofer in the group of Professors Ed Constable and Catherine Housecroft from the University of Basel.

“The discovery that zinc dyes can be used is most unexpected,” explained Professor Constable  because most chemists consider zinc to be a ‘boring’ element, as most of its compounds are colourless. However, in course of other work related to next-generation lighting devices, the research team including  Nik Hostettler and Ewald Schoenhofer were led by Professors Ed Constable and Catherine Housecroft discovered new highly-colored organic compounds that could bind to zinc to give new coloured materials. Although the devices are not yet particularly efficient, the observation opens the way to new generations of DSCs with hitherto unconsidered types of dyes.

Conventional DSCs use ruthenium dyes, but ruthenium is very rare and expensive (3,500 Swiss Francs/2,990 Euro per kilogram). Recently, the research team demonstrated that dyes from abundant and relatively inexpensive copper (7.5 Swiss Francs/6.3 Euro per kilogram) were effective in DSCs and the extension to cheap zinc (1.8 Swiss Francs/1.5 Euro per kilogram) compounds further increases the sustainability of the materials science.

"This is a significant step towards our dream of coupling photovoltaics and lighting in an intelligent curtain which can store solar energy during the day and function as a lighting device at night. This is at the core of our ERC research programme Light-In, Light-Out," commented Constable.

More information about the research is published in Chemical Communications
http://dx.doi.org/10.1039/c2cc31729j