Fraunhofer ISE has achieved a breakthrough with the world's most efficient silicon perovskite tandem solar module, boasting 25% efficiency and 421 W output on a 1.68 m2 area. The module, produced at its factory in Brandenburg, Germany, incorporates perovskite silicon tandem solar cells from Oxford PV, reaching 26.8% efficiency. Oxford PV aims for commercial production this year. Overcoming challenges, the research team optimized the manufacturing processes at Fraunhofer ISE's Module-TEC, using existing mass production equipment. It addressed perovskite layer temperature sensitivity through innovative low-temperature interconnection and encapsulation methods. Calibration involved a new multispectral solar simulator, and ongoing efforts focus on certifying the PV module and ensuring long-term stability through intensive climate chamber tests at TestLab PV Module, Fraunhofer ISE.