Integrated Molecular and Optical Materials Design for High‐Efficiency Perovskite/Si Tandem Cells

ABSTRACT Perovskite/Si tandem (PST) cells have recently achieved record‐breaking efficiencies, positioning them as a leading technology in next‐generation photovoltaics. However, maintaining long‐term operational stability and ensuring consistent performance under realistic fabrication and deployment conditions remain critical challenges. To overcome these issues, we propose a dual optimization strategy that integrates electrical interface engineering with tailored optical design. First, we introduce a novel self‐assembled monolayer containing a propoxyphenyl‐based linker, which enhances molecular packing density and significantly increases the shunt resistance of the device. This interface modification improves hole selectivity and broadens fabrication tolerance by increasing the allowable range of current mismatch between sub‐cells while maintaining high efficiency. Second, we design a light‐scattering film by embedding shape‐controlled phosphor particles into a textured poly(dimethylsiloxane) (PDMS) matrix, which improves light harvesting through UV down‐conversion and diffuse transmission. As a result, we achieve a PCE of 31.66% for a 1 cm 2 device. These findings demonstrate a synergistic design approach and offer a practical route toward robust, high‐efficiency PST devices with improved fabrication tolerance.