At the laboratory, perovskite solar cells already reach efficiencies above 25 percent. Compared to silicon solar cells of similar efficiency, the initial materials used in the former case are cheaper and production methods are simpler. So far, however, this has only been true on the small scale. “Commerciali­zation of this technology is still prevented by lacking stability of the modules and the difficulty to transfer the high effi­ciencies reached on small to larger scales,” says Ulrich W. Paetzold from the Institute of Micro­structure Technology at Karlsruhe Institute of Techno­logy (KIT). But this is the pre­requisite for the technology to lead to the development of cost-efficient solar modules. The perspective is attractive, as many of such modules might be inte­grated in still unused parts of buildings, such as facades.

For such use, costs and efficiency play a role, as do the looks. For this reason, the team of Paetzold, in cooperation with industry partner Sunova­tion, studied an inkjet method to color the perovs­kite solar modules. Its advantage: Coloring the modules by inkjet printing is inex­pensive and also suited for larger surfaces. The chosen approach has a second major advantage: “So far, color impression of colored perovskite solar cells has been dependent on the angle of the incident light,” project coor­dinator Helge Eggers explains. “With our method, the color is nearly inde­pendent of the angle of incident solar radiation and always looks the same,” Eggers adds. In a large series of experiments, researchers proved that the method originally developed for silicon solar modules can also be applied effi­ciently to perovskite solar modules. Solar cells colored cyan, magenta, and yellow reached up to 60 percent of the original effi­ciency when converting solar energy into power.

The third advantage: As inkjet printing is used, colors can be mixed. This does not only lead to a wide spectrum of colors, but it is also possible to print complex color patterns. Researchers produced solar modules looking like various building materials. Perovskite solar modules with white marble optics reached a very high efficiency of up to 14 percent. “In case of building-inte­grated photo­voltaics, the photovoltaic system will not be installed on roofs or facades, but replaced by a module. As a result, additional costs are avoided,” Eggers says. “For building-inte­grated photo­voltaics it can be stated that an inte­grated solar cell of small efficiency is better than a wall supplying no power at all. In this respect, an efficiency of 14 percent is enormous.” (Source: KIT)

Reference: H. Eggers et al.: Perovskite Solar Cells with Vivid, Angle-Invariant, and Customizable Inkjet-Printed Colorization for Building-Integrated Photovoltaics, RRL Solar, online 8 January 2022; DOI: 10.1002/solr.202100897

Links: Light Technology Institute, Karlsruhe Institute of Technology KIT; Karlsruhe, Germany • SUNOVATION Produktion GmbH, Elsenfeld, Germany