Tailored colloidal size and crystallization kinetics for high-efficiency carbon-based perovskite solar cells

Although perovskite solar cells (PSCs) show great potential, their commercialization is still hindered by challenges such as non-uniform crystallization and high defect densities in perovskite films, caused by disordered colloidal aggregation and rapid crystallization processes. In this study, we introduce methylenediammonium chloride (MDACl₂) and rubidium chloride (RbCl) into the lead bromide (PbBr₂) precursor solution. The acidic environment generated by the decomposition of MDACl₂ promotes the dissolution of colloids, resulting in smaller and more uniform colloid sizes. Additionally, the decomposition products of MDACl₂ can form complexes with Pb²⁺, enhancing the stability of the colloid by increasing steric hindrance. Rb⁺ ions, acting as crystal growth inhibitors, slow the rate of crystal growth. As a result, the PbBr₂ film possesses more uniformly distributed pores, providing an excellent foundation for the subsequent formation of large-grain, low-defect perovskite films. Carbon-based CsPbBr₃ PSCs based on this crystallization approach achieve a power conversion efficiency (PCE) of 11.36 %, representing the highest PCE reported for CsPbBr₃ PSCs. And it retain over 96.4 % of its initial PCE after continuous illumination at the maximum power point (MPP) for 488 h.