German researchers develop solvent-free perovskite-silicon tandem solar cells

Researchers in Germany have developed a fully solvent-free perovskite-silicon tandem solar cell, achieving a power conversion efficiency of 27.1%. The manufacturing process, led by the University of Freiburg and the Fraunhofer Institute for Solar Energy Systems (Fraunhofer ISE), utilizes physical vapor deposition (PVD) and sequential evaporation to deposit the perovskite layer.

This solvent-free approach is designed to be industrially scalable, as it eliminates the need for liquid carriers, reduces contamination risks, and removes the requirement for subsequent drying steps. The technology also demonstrated significant stability, retaining 97.06% of its initial efficiency after 6,800 hours of dark storage under nitrogen.

Tandem solar cells aim to overcome the physical limitations of traditional silicon cells by combining materials with different bandgaps. While silicon absorbs a large portion of the solar spectrum, much of the energy in the short-wave spectrum is lost as heat. By layering a wide-bandgap material like perovskite over a narrow-bandgap material like silicon, the cells can capture a broader spectrum of sunlight, significantly increasing potential energy yield.