In an era when the space industry is experiencing unprecedented expansion, and the number of satellites in orbit is growing at an exponential rate, the issue of the sustainability of space technologies is ceasing to be just a futuristic concept and is becoming a necessity. While public attention is often directed towards spectacular rocket launches, the real revolution is taking place in the silence of laboratories, at the microscopic level of the components that keep these satellites alive. At the center of this quiet revolution lies a key component of every space system – the solar cell.

For decades, highly efficient III-V multi-junction solar cells have represented the gold standard for powering satellites. Their superior efficiency and outstanding resistance to extreme radiation conditions in space make them indispensable. However, behind these performances lies a "dirty" secret: their production is extremely resource-intensive, energy-intensive, and generates significant amounts of chemical waste. Such practice comes into direct conflict with the new, ambitious goals of the "Green Space" initiative and the general trend of sustainability in technology.

In response to this challenge, a team of experts from the German institute Fraunhofer ISE, with strong support from the European Space Agency (ESA) through its "Discovery & Preparation" program, is developing an innovative approach to microfabrication. Their goal is radical: to replace traditional, expensive processes with a new "mask-and-plate" method that promises a transformation of the way we produce energy for space.

Dominance of III-V technology and its cost

Ever since the late 1990s, photovoltaic cells based on III-V semiconductors have sovereignly ruled the space sector. Unlike the silicon panels we see on house roofs, these cells use complex combinations of elements from the third and fifth groups of the periodic table of elements. The reason for their dominance lies in physics: they are capable of converting a significantly higher percentage of sunlight into electrical energy and, what is even more important, they can survive bombardment by high-energy particles in orbit without drastic loss of performance.

These devices are produced by the process of epitaxy – the precise growth of extremely thin semiconductor layers on a germanium (Ge) substrate. Imagine it as stacking layers of a cake at the atomic level, where every layer must be perfect. After the growth of layers, the phase of manufacturing the cells themselves follows. Although this approach is technologically mature and compatible with the harsh conditions of vacuum and extreme temperatures, it carries a high price, not only financial but also environmental.

Intensive resource consumption stems from three key factors that are deeply rooted in today's industrial practice:

• Dependence on germanium: Germanium substrates are rare and expensive, and their processing requires significant energy.


• Epitaxial growth: The process of creating layers itself consumes vast amounts of energy to maintain the necessary conditions of high temperatures and vacuum.


• Microfabrication: Final processing includes photolithography and metal evaporation. These steps are production bottlenecks – they are slow, expensive, and energy-inefficient.

The Challenge: How to reconcile efficiency and sustainability?

While on Earth the production of silicon solar cells has developed into a highly optimized industry that pays attention to material utilization, these processes cannot simply be copied for space needs. Materials and techniques that function in mild conditions on Earth would often fail in the ruthless environment of space, where drastic temperature fluctuations and cosmic radiation rule. Therefore, mere adaptation of terrestrial technologies is not an option.

Researchers have already achieved certain progress in the area of substrate reuse and more efficient epitaxial processes. However, the third pillar – microfabrication – remained largely untouched by innovations, until now. Traditional photolithography, the process of transferring geometric patterns onto a substrate using light, requires the use of photoresists, developers, and solvents, creating toxic liquid waste.

Precisely here steps in the team from the Fraunhofer ISE institute with a revolutionary idea that was originally submitted via ESA's "Open Discovery Ideas Channel" (OSIP). Their solution, named "AlternateSpace", has the potential to redefine industrial standards.

Inkjet printing: From office printers to space laboratories

The core of the innovation lies in abandoning photolithography in favor of a technology that most of us associate with printing documents or photos – inkjet printing. But, here it is not about ordinary ink. The research team developed a method that uses specialized inks (hotmelt inks) as a mask for further processing.

This approach, known as "mask-and-plate", brings a series of key advantages that directly address sustainability problems:

Primarily, the use of "hotmelt" inks eliminates the need for toxic and photoactive materials that are inevitable in photolithography. The ink is applied directly to the surface of the cell in a precisely controlled pattern. Since it is an additive process – material is added only where it is needed – the amount of waste is drastically reduced.

Furthermore, this method removes the need for steps of wet-chemical development. In classic production, after illuminating the photoresist, it is necessary to chemically remove unnecessary parts, which creates significant amounts of hazardous waste. Inkjet printing simply skips that step, significantly simplifying the production chain and reducing the factory's ecological footprint.

Revolution in metallization: Galvanization instead of evaporation

The second key element of this innovation relates to the way metal contacts are created on the solar cell. In the conventional process, metal evaporation in a vacuum is used, a process that consumes a lot of energy and materials because the metal is deposited over the entire surface, and then the excess is removed (lift-off process).

Fraunhofer ISE's new approach replaces evaporation with a process of galvanization (electroplating). Here, metal is deposited electrochemically exclusively on areas where the semiconductor material is not covered by ink. This means there is no waste of precious metals and no need for subsequent removal of excess material.

However, the path to this solution was not simple. It required extensive optimization of every parameter. Researchers had to test different types of inks and adjust variables such as print resolution and temperature to achieve reliable, microscopically small openings for contacts. The chemical compatibility of the mask was a critical point; it had to withstand different electrolytes, temperatures, and pH values during the galvanization process without degradation.

Quest for the perfect metal: Nickel-Phosphorus

A special challenge was presented by the metallization itself. For space applications, materials must not be ferromagnetic because they could interfere with the magnetic field of the Earth (or other bodies) and cause unwanted rotations or disturbances in satellite navigation. Standard nickel, which is often used in electronics, is a magnetic material.

The team therefore explored and successfully implemented nickel-phosphorus (NiP) as a non-ferromagnetic alternative. This material serves as a barrier and adhesive layer. The final pattern design includes front contacts made of silver applied onto a layer of nickel-phosphorus. Tests have shown that this combination is not only electrically efficient but also completely compatible with the extreme requirements of the space environment.

Expected results and a look into the future

After defining a complete process route that integrates all newly developed steps – from inkjet printing of the mask to selective galvanization – the project enters the final phase of demonstration. According to the team's announcements, a fully functional photovoltaic cell produced without photolithography, with metal contacts applied by space-compatible galvanization, is expected as the crown of this research cycle.

This technological breakthrough comes at a crucial moment, today, December 5, 2025, when the space industry is under increasing pressure to reduce costs and increase sustainability. Massive satellite constellations in low orbit require thousands of solar panels, and current production capacities and costs represent a bottleneck.

Oliver Höhn, head of the group for III-V semiconductor technology at the Fraunhofer ISE institute, emphasizes the importance of this achievement: "By replacing photolithography and metal evaporation with scalable inkjet printing and galvanization, Fraunhofer ISE demonstrates a simplified process with significantly reduced chemical waste. This approach is aligned with the goals of 'green space' sustainability and cost reduction. After the successful demonstration of this approach, our goal is collaboration with the industry to further develop, stabilize, and finally scale the process towards industrial realization."

Similar optimism is shared by Erminio Greco, engineer for solar generators at the European Space Agency (ESA): "This work marks a key step towards cost-effective, sustainable, and efficient III-V solar cell technology. It paves the way for a scalable and economically viable production route for the next generation of space photovoltaics. The results of the activity highlight the key role of ESA's Discovery & Preparation program in generating new ideas that can spur the development of future space technologies."

Broader context: Green Space

The "AlternateSpace" project is not an isolated incident of innovation, but part of a broader strategy. The "Clean Space" initiative of the European Space Agency has already been working for years on assessing the impact of space missions on the environment, both on Earth and in space. The introduction of technologies that reduce the energy footprint of component production directly contributes to these goals.

The transition to inkjet printing and galvanization could reduce energy consumption in solar cell production by a significant percentage, while the elimination of toxic chemicals would facilitate compliance with strict EU environmental regulations, such as the REACH regulation. Besides ecological benefits, the economic calculation is clear: cheaper production means cheaper satellites, which ultimately enables more affordable space services, from internet and communications to Earth observation and climate change monitoring.

In a world where resources must be used ever more smartly, technology that combines the precision of German engineering with the vision of a sustainable space shows that it is possible to reach the stars without destroying the planet we start from. Fraunhofer ISE and ESA prove with this project that the future of space energy is not only in greater efficiency, but also in smarter, cleaner, and more responsible production.