Laser-assisted growth of ligand-free nanocrystals for grain-boundary passivation and suppression of non-radiative defects in lead-free Cs₃Sb₂I₉ solar cells

Antimony-based lead-free perovskite Cs₃Sb₂I₉ suffers from poor formation of the two-dimensional layered phase, high defect density, and limited photovoltaic performance. Here, we reported a synergistic strategy combining SbI₃ vapor-assisted annealing and ligand-free ultrafast femtosecond pulsed laser ablation of liquid precursor (PLALP) to regulate crystallization kinetics and defect chemistry. The SbI₃ vapor-assisted annealing suppresses SbI₃ volatilization and promotes the formation of high-quality layered Cs₃Sb₂I₉ films. Meanwhile, Cs₃Sb₂I₉ nanocrystals are generated through ligand-free PLALP to effectively passivate grain boundaries and non-radiative defects. As a result, the films exhibit enhanced crystalline, improved perovskite grain formation, reduced surface roughness, and suppressed defect states, leading to prolonged carrier lifetime and reduced non-radiative recombination. Consequently, the optimized devices delivered a short-circuit current density (J_sc) of 6.54 mA/cm², an open-circuit voltage (V_oc) of 0.893 V, a fill factor (FF) of 59.76%, and a power conversion efficiency (PCE) of 3.49%. Notably, the unencapsulated devices retain over 90% of their initial PCE after 1400 h of ambient storage based on intermittent photovoltaic measurements and exhibit reduced hysteresis as well as improved photostability under ambient conditions. This work provides a viable pathway for defect management and stability enhancement in lead-free perovskites.