The material has a detectivity level comparable to amorphous silicon, which is widely used in large-area electronics applications, such as liquid-crystal displays (LCDs).
Stupp and his research team designed a novel nanoscale architecture that places the inorganic component (zinc oxide) right next to the organic component, with this pattern alternating over and over, like pages in a book. The pages are packed very tightly.
Each organic page -- which can be one of thousands of different types of molecules -- absorbs light, and an electron is transferred directly to the zinc oxide page, generating current. This works -- and works extremely efficiently -- because the organic and inorganic components are so close together.
To build a book, the researchers grow a precursor material to zinc oxide in the presence of self-assembling organic molecules. (The material can be grown on any metallic or conducting substrate.) The precursor, zinc hydroxide, is formed using electrodeposition and then thermally converted to zinc oxide. Each zinc oxide page is a nanometer thick while the organic page is one to two nanometers thick, depending on the molecule being used.
In the Nature Materials paper the researchers demonstrate that they can build orderly books with high detectivity. But in order for their materials to be used for solar energy, Stupp says, they must build entire "macroscopic libraries" of these books. And, like the books, the libraries must be highly ordered.
"Right now our library is a little disordered, but we are working on optimizing our materials for use in solar energy devices," said Stupp, director of the Institute for BioNanotechnology in Medicine at Northwestern.
|Contact: Megan Fellman|