09 August 2012
Plansee today announced it has developed two molybdenum alloys: molybdenum-sodium (MoNa) and molybdenum-tantalum (MoTa).
Plansee will present the alloys at the EU PVSEC 2012 in Frankfurt, 24-28 September, hall 3.0, F29.
Because of its good adhesion to glass and high level of electrical conductivity, molybdenum is used as a CIGS back contact.
Small amounts of sodium in the CIGS absorber improve the efficiency of the solar cell. In the case of glass-based CIGS modules, the soda-lime glass usually also acts as the sodium source. During the production process, sodium from the glass diffuses through the molybdenum back contact into the absorber layer.
However, this process is not easy to control and the sodium is often unevenly distributed.
Sputtering targets made from sodium-doped molybdenum (MoNa) offer an alternative. A thin MoNa layer is sputtered above or below the molybdenum back contact. This MoNa layer is then responsible for the controlled release of sodium that occurs as the CIGS absorber is being formed. The concentration of sodium in the absorber can be precisely adjusted by varying the thickness of the layer.
Tests conducted in cooperation with EMPA, the Swiss Federal Laboratories for Materials Science and Technology, have confirmed the effectiveness of sodium doping using MoNa layers, according to Plansee.
Molybdenum can oxidize in corrosive atmospheres, which the company says it why it has developed targets made from molybdenum-tantalum, a corrosion resistant material.
In addition to MoTa and MoNa, Plansee will present its coating material for CIGS absorber layers and chromium targets for the production of diffusion barriers at EU PVSEC.
At the PV Production Forum held during EU PVSEC, Dr. Christoph Adelhelm, application group manager for solar at Plansee, will talk more about the new materials for CIGS layers. His address will take place 26 September from 3:40 p.m. to 4:00 p.m. in hall 4.