Scalenano is a FP7 funded project with a large consortium of partners. The main aim of the project is to raise the efficiency of thin film photovoltaic devices made from chemical low cost processing methods. In particular the aim of LEM within the project is to create high quality earth abundant p-type absorber layers by using electrodeposition and annealing.
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The aim of the LASER project is to investigate whether lasers can be used to

  • synthesise high quality semiconductors from electrodeposited precursors and
  • anneal out defects in already completed semiconductor absorber layers



The CEDIL project aims to investigate the suitability of ionic liquids to electrodeposit semiconductor precursors or even semiconductors directly. Ionic liquids have two main advantages over aqueous solvents. They may be used at much higher temperatures, up to 200°C, and have much wider windows of electrochemical stability. This means that elements such as gallium can be easily deposited using ionic liquids.



Electrochemical deposition

The low cost process: Thin film semiconductors can be fabricated using a two stage process known as electrodeposition and annealing. In the first stage the elements required for the semiconductor are deposited onto a conducting substrate from a solution to form precursor layers. The precursor layers are taken from solution, dried, and transferred into an annealing oven. Inside the annealing oven they are heated for a short period of time up to temperatures of between 500 and 600 °C. During the annealing process the semiconductor is formed, and once it is cooled down to room temperature it can be subsequently further processed to make a full solar cell.

The substrates for the precursor layer must be conducting, and can be metal layers on glass, or consist of a flexible metal foil. The precursor layers consist of the elements required to form the semiconductor. These elements can be deposited onto the substrate in a number of ways. All the elements may be deposited together at once, or they can be deposited separately in a stacking process. Thin film semiconductors that we make contain metals and either sulfur or selenium. These elements can be electrodeposited directly, or later introduced in the annealing process. The precursors are annealed in an oxygen and water free environment, normally with a background vapor of sulfur or selenium.