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Gradient multilayer nanofilm
From Wikipedia, the free encyclopedia
Gradient multilayer (GML) nanofilm is an assembly of quantum dot layers with a built-in gradient of nanoparticle size, composition or density.
Properties of such nanostructure are finding its applications in design of solar cells[1][2][3] and energy storage devices.[4]
The GML nanostructure can be embedded in the organic material (polymer), or can include quantum dots made of two or more types of material.
![](http://upload.wikimedia.org/wikipedia/commons/c/c1/GMLnanofilm.png)
Photovoltaic applications
The GML nanofilm only 100 nanometers thick can absorb the entire Sun spectrum (0.3–2.0+ eV). At the same time, gradient of the quantum dots size can create a gradient of the electrochemical potential, acting as an equivalent of built-in electric field inside a nanofilm. This enhances transport of electrons and holes, and improves internal quantum efficiency (IQE) and photocurrent.
Manufacturing
The industrial manufacturing of GML nanofilms represents a challenge. Traditional methods of building nanostructured materials (like spin coating) can't form GML nanostructures, while more effective methods like Atomic Layer Deposition (ALD) or Langmuir-Blodget "microchemical" method.[5] are expensive.