Christopher Höfener and the price of a yellow crystal

Christopher Höfener wanted to make hydrogen in a country that could hardly be accused of having too much sunshine. Germany was part of the point. In 2023, the co-founder of The Yellow SiC Group was explaining an ambition to produce renewable hydrogen at a competitive price even where the weather offered less assistance. The proposed shortcut was a yellow semiconductor. Sunlight would meet water at a specially engineered material, and hydrogen would emerge without a separate electrolyzer.

It was an arresting proposition from someone who had spent years in private equity. Höfener had helped finance and manage companies through difficult changes. Now he was helping build a business around a different kind of change: persuading a material to perform reliably, then finding a way to manufacture it. A financing model can be revised before lunch. A reactor generally requires more notice.

His career makes the move less improbable than it first appears. Before the investment firms came mathematics and physics. Before the yellow crystal became a company, he had worked on the practical business of making other companies function. The connection is production: what something can do, what it costs to make, and whether anyone will buy enough of it.

The factory before the fund

Höfener studied mathematics and physics at the University of Bielefeld and earned his doctorate at the Technical University of Darmstadt. His early career took him to McKinsey. His later Perusa biography named Munich, Düsseldorf and Chicago among the places where he had worked for the consultancy. That combination put technical study beside the less orderly problems of running a business.

By 2003, he was advising Bally Wulff, the Berlin gaming-machine manufacturer, following a change of ownership. In September 2005, his appointment to its management from January 2006 was announced. The work described around that appointment was specific: equipment development, a surface-mount electronics production line, a new IT system and changes to sales processes. Semiconductor materials were still years away, but electronic manufacturing was already on the agenda.

At Bally Wulff, his tasks crossed the usual borders between strategy and operations. A product had to fit its market; the factory had to make it; information had to travel through the business. There is nothing particularly glamorous about an IT rollout arriving alongside a production line. There is, however, a considerable amount of management in it.

In June 2006, the company appointed Axel Herr, whose experience included Nintendo and Konami. Höfener remained a managing director but returned to owner Orlando Management in Munich, retaining responsibility for the investment. His career already moved between the investor’s chair and the operating company’s desk. The two offered different views of the same machinery.

A career in companies that needed changing

Perusa, founded in 2007, brought Höfener together with Christian Hollenberg and Hanno Schmidt-Gothan. Its founding trio offered investment and management experience to medium-sized businesses facing transitions. Their brochure dealt in expansion, succession, acquisitions and turnarounds. These were companies with existing histories, employees and problems, rather than an invention awaiting its first customer.

The firm described a fund with a term of up to 14 years. That was an explicit allowance for work that could take time: restructuring, financing growth or arranging a handover. Höfener’s biography emphasized experience with companies in challenging situations since 2003. His expertise sat at the junction where capital had to become a workable plan inside an organization.

He subsequently co-founded Marondo Capital with Stefan Elsser, Marko Maschek and Hansjörg Ruof. Marondo pursued technology-focused growth businesses in Germany and the wider German-speaking market. Its stated interests included environmental technologies, new materials, software and industrial technology. The connection to his later work was already visible in the investment brief: engineering knowledge could become the basis of a growing company.

Marondo’s model combined capital with support for development, through both majority and minority investments. For Höfener, this was another setting in which technical distinction needed a commercial route. The question carried forward into Yellow SiC: having something different is a beginning. Making the difference useful to a customer is a much longer assignment.

A yellow crystal, with two possible customers

Yellow SiC paired Höfener with Professor Siegmund Greulich-Weber, whose silicon-carbide expertise had developed at Paderborn University. Greulich-Weber supplied the material-science background and led development; Höfener was identified as co-founder and CEO in the company’s early fundraising account. Their raw material supplied a conveniently literal name. Cubic silicon carbide, abbreviated 3C-SiC, is yellow.

The energy proposition centered on photocatalysis. Instead of turning sunlight into electricity and then using that electricity in a separate electrolyzer, the proposed system would split water at a silicon-carbide electrode. It promised a shorter route from sunlight to hydrogen. The commercial challenge was to make that shorter route productive and economical outside the laboratory.

There was also a second route to revenue. In January 2023, Höfener described plans to sell silicon carbide to the ingot and wafer industry while developing hydrogen generation. The company had raised €4 million from investors including PVS Investments, conenergy, Vireo Ventures and its founders. Its ambitions therefore included both an energy system and the material from which other manufacturers could build.

Conenergy’s investment announcement that month highlighted Höfener’s desire to make the hydrogen economics work in less sunny countries. The geography mattered: a design dependent on exceptional sunshine would answer a narrower question. Germany was to be a proving ground for the idea, with an Osnabrück pilot then planned for early 2025.

The figures attached to the hydrogen proposal were projections. Six cents per kilowatt-hour in Germany was a company target. A proposed installation date described an intended next step. Both belonged to a development program, where the distance between an attractive calculation and a repeatable result must be crossed with equipment.

The material gets a vote

The technical work gives this career change its substance. A DBU-funded project developed and tested silicon-carbide electrodes, with attention to porosity, electrical behavior and unwanted impurities. The research described microscopic structures that increased active surface area by more than a factor of 200 compared with flat layers. More surface was useful only alongside the other properties the electrode needed.

Doping, the deliberate introduction of selected atoms, required careful control. Aluminium was used for p-type doping; unwanted nitrogen had to be reduced. Measurements investigated residual impurities into the sub-parts-per-million range. Such details are where the neat phrase “sunlight and water” acquires its engineering bill. The simplicity belongs to the intended user experience. Producing the material is exacting work.

“We are now working on scaling up the manufacturing processes for the electrodes.”Christopher Höfener, 2024

By late 2024, more than €8 million had been raised for development, with a substantial contribution from Höfener’s own assets. He described the immediate task as increasing electrode production beyond laboratory quantities. His investment experience had become personal financial exposure to the work. That is a concrete commitment, without requiring a heroic account of what it felt like.

A subsequent DBU-supported project ran from October 2023 to January 2025. It optimized electrode production and developed a prototype while investigating efficiency, durability and economics. One design idea proved too costly and complicated: routing a separate solar-thermal circuit through the electrodes. An external heat exchanger offered a better arrangement. The engineering changed in response to the experiment.

The project’s conclusion placed the prototype near the beginning of its development. This is a useful measure of progress: processes had been developed, laboratory systems assembled and design choices revised. The machine was becoming more specific. A prototype can be valuable precisely because it reveals which appealing ideas should leave the drawing.

The next address is a steelworks

In September 2026, the business acquired a new industrial setting. Saarland’s steel industry and the state participated in Y-SIC, supporting its first commercial silicon-carbide production plant on Dillinger’s works premises. The announced purpose was continuous production of high-purity powder at industrial scale, creating a European supply option for a strategically important material.

This brought the material-sales strand of the early plan into sharper focus. Today Y-SIC presents its process around semiconductor feedstock and the beginning of the production chain. Powder quality feeds into crystal growth, wafer quality and device yield. For Höfener, the commercial problem now has a familiar industrial shape: turn a distinctive process into dependable supply.

The leadership description has also changed. The September announcement names Alexander Zeyss as CEO. The company’s imprint continues to list Höfener and Greulich-Weber as authorized managing directors. The distinction matters in a career story that spans several stages of a company: co-founding, early fundraising and the next phase of industrial production involve overlapping people and changing responsibilities.

Höfener’s route to this point runs through consulting offices, gaming machines, investment partnerships and electrode development. Its continuity is practical. He has repeatedly worked where a technical or organizational proposition needs money, management and a means of delivery. At Yellow SiC, those questions converge on a powder and the machinery that must produce it.

The yellow crystal has already carried a large ambition: hydrogen made where the sunshine is imperfect. It now carries a factory plan as well. For an investor who became a co-founder, that is a demanding place to stand. The next argument will be made by the production process, one run after another.