In what is considered to be a first in new materials science, a team of engineers at the Brookhaven and Los Alamos National Laboratories have created a light-absorbing material that efficiently generates charge and charge separation. What’s more, these “films” are transparent, making them perfect for windows. Soon, perhaps, your windows will be your main source of household power.
The thin film material is a blend of semiconducting polymer doped with fullerenes (a fullerene*, C6o, is an ordered, 60-sided, “spheric”, carbon structure). Under strictly controlled conditions, the concoction self-assembles into a regular pattern of micron-sized, hexagonal cells (see diagram below). The film thus “grows” to cover a relatively large area of several millimeters.
- Top: Scanning electron microscopy image and zoom of conjugated polymer (PPV) honeycomb. Bottom (left-to-right): Confocal fluorescence lifetime images of conjugated honeycomb, of polymer/fullerene honeycomb double layer and of polymer/fullerene honeycomb blend. Efficient charge transfer within the whole framework is observed in the case of polymer/fullerene honeycomb blend as a dramatic reduction in the fluorescence lifetime.
The next logical step in this pioneering effort is a large-scale patterning process to efficiently cover larger areas — such as a pane of glass. The honey-comb patterning and “packing” of the thin-film, manufacturing technique relies on the evaporative effects of water (the solvent) when combined with the polymer/fullerene solution. This evaporative effect of water on the polymer solution also determines the rate of charge transport through the material. Thus, also, water usage may become an issue for large scale production of these films.
Buckminsterfullerene C60 (top), “buckyball”, and carbon nanotubes (bottom) are two examples of structures in the fullerene family.
The material remains transparent because the polymer chains are most densely packed at the edges of the hexagons, with very low density packing in their centers, allowing ample light to pass through the tiny, geometrical structure.
Engineering team members are Mircea Cotlet, Ranjith Krishna Pai, and Zhihua Xu.
The research was conducted jointly at The Center for Functional Nanomaterials at Brookhaven National Laboratory and the Center for Integrated Nanotechnologies Gateway to Los Alamos facility. These are two of the five DOE Nanoscale Science Research Centers (NSRCs), our nation’s top user facilities for interdisciplinary research at the nanoscale.
The NSRCs constitute the largest infrastructure investment of the National Nanotechnology Initiative. The five NSRCs are located at DOE’s Argonne, Brookhaven, Lawrence Berkeley, Oak Ridge, and Sandia and Los Alamos national laboratories.
Read more about this new material development (and manufacturing process) at Transparent Conductive Material Could Lead to Power-Generating Windows
*The fullerene takes its name from R. Buckminster Fuller, inventor of the geodesic dome and many other concepts, who predicted its existence years before its discovery; the predicted polyhedral (60 Carbon atom) structure was based upon his Synergetics system of geometry. Fuller took up the issue of sustainability, and long-term evolutionary utility, in his 1981 book Critical Path. He also coined the phrase “spaceship Earth”.
Top Image: Etan J. Tal; cc – by 3.0
Microscopy Images: the authors, DOE Broohaven/Los Alamos Laboratatories
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