Synergistic Modulation of Crystallization Kinetics and Interface Energy-Level Alignment for Efficient Perovskite/Silicon Tandem Solar Cells.

Abstract

Increasing bromine content is a common strategy for widening the bandgap of perovskite materials. However, this often accelerates crystallization, thereby degrading film quality and energy-level alignment. To address this, we introduce the multifunctional molecule 2-amino-4-cyanobenzoic acid (2A4CBA) into a 1.68 eV perovskite precursor to simultaneously modulate crystallization and energy-level. The 2A4CBA interacts with perovskite precursors via coordination and hydrogen bonding through its amino, cyano, and carboxyl groups. These interactions significantly delay crystallization, broaden the processing window, and promote complete reaction between lead halide and salt, thereby reduced residual unreacted lead iodide and ultimately yielded high-quality perovskite films with larger grains and lower defect state density. Moreover, 2A4CBA differentially modulates the work functions of top surface and buried interface, establishing a graded energy-level alignment that facilitates separate extraction of electrons and holes. As a result, the single-junction inverted wide-bandgap (WBG) perovskite solar cell (PSC) achieved a power conversion efficiency (PCE) of 23.44% along with markedly improved storage and operational stability. Furthermore, a 1 cm² perovskite/silicon tandem solar cell (TSC) integrating this optimized WBG perovskite reached a PCE of 33.20% (certified 32.88%) and exhibited excellent operational stability.