Franklin's Plansee Shows Way to Future Solar Tech

Imagine hiking through remote landscapes and charging your smartphone with a flexible solar panel on your backpack. Or picture an aircraft that needs less fuel thanks to solar energy. All this is possible, according to a story posted by Austrian firm Plansee,  with CIGS (copper indium gallium selenide) thin-film technology, which works where conventional silicon modules reach their limits.

An indispensable component in realizing this is a defined molybdenum layer, applied in a precise coating process. This layer ensures stability, a high degree of conductivity, and enhanced efficiency of the solar cell—even in extreme conditions.

Why CIGS? The advantages at a glance

In contrast to traditional silicon modules, CIGS modules are up to twenty times thinner, significantly lighter, and in some cases even flexible. They deliver reliable performance even in diffuse light conditions, meaning that they work on cloudy days and in shaded urban areas, for example.

Thanks to these properties, CIGS modules can be used for new and additional applications where silicon modules are unsuitable:

• Building integration: Facades and roofs with seamlessly integrated solar modules
• Mobility: Integration into car roofs or truck trailers
• Outdoor applications & emergency assistance: Folding solar panels for camping, parasols or carports, and in disaster zones
• Aviation and aerospace: Drones, satellites, and experimental aircraft

Molybdenum—the backbone of CIGS technology

At the heart of CIGS solar cells is a molybdenum layer just under 100 nm thick, which serves as a counter electrode for current collection. It ensures:

• Thermal stability during the manufacture of solar cells
• Sufficient adhesion and conductivity between the substrate (glass or plastic) and the active layer
• Lower electrical resistance thanks to an MoSe₂ intermediate layer

The molybdenum layer is applied by sputtering—a process in which molybdenum atoms are removed from a sputtering target in a vacuum chamber and transferred to the substrate. Modern tubular and rotary targets increase material utilization and reduce production costs in comparison to plate-shaped static targets.

Plansee innovation: precision in molybdenum

For CIGS to work, it requires a perfect counter electrode—and this is where Plansee comes in.

Our products and solutions:

1. Molybdenum sputtering targets

• Molybdenum sputtering targets: high purity: ≥ 99.97%, maximum density: > 99.5%, homogeneous microstructure, high sputtering speed, and flawless thin film production
• Monolithic molybdenum rotary sputtering targets: high metallic purity (> 99.97%), high density (> 99.5%), homogeneous microstructure, high production throughput for customers thanks to increased power consumption
• Sodium-doped molybdenum sputtering targets: increased efficiency of CIGS solar cells through sodium doping. Homogeneous and targeted sodium distribution for stable coating, high purity and density for homogeneous microstructure, available in various dopant levels (e.g., 5% or 10% Na), suitable for planar and rotating targets

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  Molybdenum planar target

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  Molybdenum sputtering target

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  Molybdenum-sodium sputtering target

2. Components for vacuum coating systems

• Heat-resistant components such as shields, crucibles, evaporation boats, and carriers made of molybdenum or tungsten for the evaporation of CIGS layers at temperatures above 500 °C

Innovations for enhanced efficiency and greater sustainability

Groundbreaking developments such as monolithic rotary targets made entirely of molybdenum simplify manufacturing, improve recyclability, and reduce material consumption. Alkali-doped molybdenum layers made of MoNa are used for flexible modules with plastic or stainless steel substrates, which increase the efficiency of solar cells.

Molybdenum also plays a central role in the manufacture of evaporation systems for the CIGS absorber layer—for example, as a material for shields, crucibles, and carrier structures that are capable of withstanding high temperatures and harsh chemical conditions.

Looking to the future: tandem cells and a growing market

In future, CIGS could also be used in tandem solar cells together with other cell technologies such as silicon and perovskites—a promising technology that utilizes different parts of the light spectrum, thereby increasing the energy yield. While thin-film modules currently account for less than 3% of the total solar market, demand for these new technologies is growing rapidly.

According to the International Energy Agency (IEA), around 2.2 trillion US dollars will be invested worldwide in low-carbon technologies in 2025, with solar energy leading the way with a share of 450 billion US dollars. CIGS modules with molybdenum are poised to play a central role in this development for innovative niche products.