Synergistic Bulk and Interfacial Defect Control Boosts Voltage and Efficiency in Perovskite/Silicon Tandem Solar...

Open-circuit voltage (V_OC) losses caused by defect-assisted recombination and interfacial energy misalignment in wide-bandgap perovskites remain a critical obstacle for high-efficiency perovskite/silicon tandem solar cells (PSTSCs). Here, we report a synergistic bulk-to-surface defect passivation strategy that simultaneously suppresses defect formation during the crystallization and optimizes the perovskite/C₆₀ interface. The incorporation of Dicyandiamide into the precursor significantly improves vacancy formation energies and enhances perovskite crystallinity, while subsequent surface treatment with ethane-1,2-diamine diacetate enables the concurrent passivation of cationic and anionic defects and induces favorable energy-level alignment. This coordinated defect management substantially reduces nonradiative recombination loss, yielding monolithic PSTSCs with a champion power conversion efficiency of 32.03% and a high open-circuit voltage of 1.95 V along with exceptional storage stability under ambient conditions. These results demonstrate that the integrated bulk and interfacial defect control is essential for approaching the voltage and efficiency limitation of the wide-bandgap perovskite top cells for tandem photovoltaics.