Researchers in China have developed a novel 2D seeding agent, CsPb2Br5, to regulate crystallization in wide-bandgap perovskite films, achieving an efficiency of 31.13% in perovskite-silicon tandem devices. This seeding agent addresses issues of uncontrollable crystallization and phase separation, promoting top-down vertical crystal growth to enhance charge transport and suppress phase separation. The optimized wide-bandgap perovskite also shows high power conversion efficiency and stability compared to control devices, with potential for use in large area devices. Co-corresponding author Wei Huang emphasized the focus on optimizing long-term stability for future applications.