Fraunhofer Institute for Microstructure of Materials and Systems IMWS
The aesthetic integration of photovoltaics into buildings and urban spaces is considered a key factor in unlocking previously unused solar potential. Especially in cities, with listed buildings, or in the area of balconies and façades, conventional dark-colored standard modules often face acceptance issues. This is where the new project “COLIPRI” of the Fraunhofer Center for Silicon Photovoltaics CSP in Halle (Saale) comes in. The project explores a coloring process that enables commercially available, cost‑effective PV modules to be individually retrofitted with color while keeping color‑related efficiency losses low.
In 2023, more than one million new PV systems were installed in Germany. Despite this momentum, the potential remains far from exhausted, particularly in urban areas and in building‑integrated (BIPV) and building‑attached photovoltaics (BAPV). The Solar Atlas of the German Aerospace Center indicates an annual potential of around 22 TWh from solar roofs in Saxony‑Anhalt. However, from an architectural perspective, the standard modules available today are not always suitable. “If photovoltaics are to become part of our built environment, they must be practically adaptable in design - without causing excessive efficiency losses,” emphasizes Dr. Charlotte Pfau, project manager at Fraunhofer IMWS. Existing solutions for colored PV modules are either costly, limited to standardized designs, or associated with significant performance losses. Against this background, there is strong interest in individually customizable, efficient, and cost‑effective photovoltaic modules.
The goal of the project is therefore to develop a process for retrofittable, individually customizable coloring of commercially available PV modules that ensures high module efficiency (> 75% compared to unprinted reference modules). The core approach is the combination of low‑cost standard modules with printed front sheets or cover glass, which can be produced independently of large‑scale module manufacturing and subsequently retrofitted without causing damage.
Technically, the focus is on researching novel ceramic colors and digital printing processes. A glass‑ceramic matrix of the color layer is intended to achieve high reliability and long‑term stability, while spectrally selective pigments - including ceramic interference pigments - are used to minimize efficiency losses. In addition, new printing grid concepts are being developed to reduce coverage and absorption, thereby further optimizing the energy yield of colored modules. Laminating and alternative module assembly processes for glass, thin glass, and polymer films are being investigated in parallel, tailored to different applications such as facade, roof, or balcony modules.
Within the project, Fraunhofer CSP is responsible for the overall design and evaluation of the colored retrofit solutions for PV modules. The institute develops efficiency‑optimized printing grids and optical layer stacks for an appealing appearance with minimal power loss and generates the high‑resolution data sets required for this. In parallel, new, fast, and large‑area measurement methods as well as suitable test objects (laminates and mini‑modules) are being established to quantitatively capture color effect, glare, and resulting module performance - including angular dependency. A simulation tool is being developed for accelerated assessment, enabling quick estimation of expected performance losses based on image or print files and module layouts. Fraunhofer CSP also supports the project with lamination tests and process optimization on a laboratory scale and characterizes colors and printing grids regarding performance impact, appearance, damage‑free integration, and UV stability.
The project opens up the possibility of making cost‑effective PV modules with a high degree of design freedom available for the growing market of urban and decentralized photovoltaics. This not only fills an existing market gap, but also contributes to design acceptance and the continued accelerated expansion of solar energy.