Regulating Asynchronous Crystallization via Additive Coordination Enables Efficient Perovskite/Silicon Tandems

Abstract Wide-bandgap perovskites are essential for high-efficiency perovskite/silicon tandem solar cells but are limited by halide segregation and a narrow crystallization temperature window. Although temperature is known to influence perovskite film formation, its role in driving asynchronous crystallization between I-rich and Br-rich domains—and thus the extent of phase segregation—remains insufficiently understood. Here, we reveal that substrate temperature critically regulates these asynchronous crystallization pathways and propose an additive-engineering strategy to overcome this bottleneck. By introducing 2-mercapto-4-(trifluoromethyl) pyrimidine (2-MTP), the strong PbX2 coordination regulates DMSO–PbX2 intermediates, substantially broadening the processing temperature window. This controlled coordination modulates precursor conversion kinetics, mitigates asynchronous halide-rich domains crystallization, and effectively suppresses phase segregation in wide-bandgap perovskite films. As a result, 2-MTP-modified wide-bandgap devices achieve PCEs of 23.79% (1.67 eV; certified 23.02%) and 19.81% (1.84 eV). When implemented in perovskite/silicon tandem architectures, additive-regulated crystallization delivers 32.48% PCE (certified 31.60%) and markedly improved operational stability.