The CIGS solar cell consists of several thin layers which are applied by different coating processes. In a typical production process, after the contact layer of molybdenum is sputtered, the absorber materials, copper, indium and gallium are thermally evaporated and later selenized in a gas atmosphere. In various process chambers and around the evaporation sources, there are metal shields, heating elements and other parts. High demands are placed on them:
A reaction between the materials in the chambers and the aggressive process gas during the selenization results in critical contamination in the highly sensitive coating process.
Moreover, the components are regularly heated and cooled. Thermal deformation can be the result. Furthermore, process-related deposits may limit the function of the components over time. Damaged or worn parts must be replaced, repaired or cleaned.

By using refractory metals such as molybdenum, plant operators can increase the lifetime of coating systems significantly. Molybdenum not only holds up to the highest temperatures to 1800 ° C, but is exceptionally suited for use in vacuum, nitrogen, hydrogen, argon and many corrosive gas atmospheres because of its low reactivity.
The material has a very low heat capacity and thermal expansion. As a result, it can be heated and cooled quickly with low energy demand and without distortion.

The high melting point of molybdenum leads to vapour pressures which are some orders of magnitude lower compared to steel and other metals. It guarantees a clean atmosphere   and ultra-high vacuum capabilities at elevated temperatures.

Molybdenum-Lanthanum: Dimensionally stable for a longer service time
The service time of molybdenum components can additionally be improved by utilizing molybdenum-lanthanum (ML) material instead of pure molybdenum.
Doping molybdenum with small quantities of La2O3 increases the recrystallisation temperature to 1400°C / 2552°F. The resultant elongated grain structure with jagged grain boundaries improves the mechanical properties and increases the ductility considerably.

The fine La2O3 particles in ML reinforce the molybdenum matrix resulting in beneficial properties which are superior to those of pure molybdenum.
Forming must take place above the brittle-to-ductile transition temperature. This temperature depends on the deformation history and material thickness.
ML can be, like pure molybdenum, easily joined by riveting and folding. Due to their enhanced ductility ML can be machined - unlike to pure Mo – even after high temperature use, e.g. drilling for repair work. Also mechanical cleaning and sand blasting for maintenance purpose can applied to ML with less risk of part damage. Due to oxidation effects the molybdenum materials cannot be used in air above 350 °C (662 °F).

High quality molybdenum components from PLANSEE
The Austria-based company PLANSEE not only is one of the world’s leading suppliers of metallic sputtering targets. The company has also been operating high temperature processes since 1921 and delivers a broad range of customized furnace components made of molybdenum, tungsten, tantalum and their alloys.

A good number of engineers devote themselves to engineered components for highly demanding equipment in coating and thermal processes every day. They are experts in refractory metals and know exactly which factors need to be considered in order to optimize functionality. PLANSEE customizes each product to the special demands of the customer. The product portfolio covers complete heating and shielding concepts for new equipment as well as rebuilding and upgrading of existing machines.

Sheets, foils, rod and wire made of tungsten, tantalum, molybdenum and its alloys such as ML and TZM are available in different dimensions. Standard sizes can be ordered online at www.plansee-express.com.