Synergistic coordination competition and steric hindrance for crystallization control in CsPbBr3 perovskite solar cells

The performance of solution-processed CsPbBr 3 perovskite solar cells is limited by uncontrolled crystallization kinetics. Herein, we introduced acetaminophen (APAP) as a dual-functional additive that combined competitive coordination and steric hindrance. Density functional theory (DFT) calculations revealed that the carbonyl group displaced dimethylformamide (DMF) from the Pb 2+ coordination shell, reducing the coordination number from 6.0 to 4.8, whereas the rigid phenyl ring restricted ion diffusion, decreasing the Pb 2+ diffusion coefficient from 0.039 to 0.003 Å 2 ·ps −1 . This synergy suppressed burst nucleation and retarded excessive crystallization. At the optimal 5% APAP loading, the film became pinhole-free with average grain size increasing from 516 to 816 nm, and residual APAP molecules passivated Pb 2+ dangling bonds and promoted a (002)-preferred orientation. The resulting solar cells achieved a power conversion efficiency (PCE) of 9.82% with a open-circuit voltage (V OC ) of 1.53 V, significantly outperforming the control devices (7.6%, 1.37 V), and retained 98% of their initial efficiency after 30 days in ambient air. This work provides a generalizable molecular design principle integrating a coordinating carbonyl group with a bulky phenyl backbone for crystallization control in all-inorganic perovskites, offering a versatile route to simultaneously suppress trap-assisted recombination and reduce bulk defect density in solution-processed optoelectronic devices.