Abstract
Cations with suitable sizes to occupy an interstitial site of perovskite crystals have been widely used to inhibit ion migration and promote performance and stability of perovskite optoelectronics. However, the interstitial doping accompanies inevitable lattice strain to impair long-range ordering and stability of the crystals to cause a sacrificial trade-off. Here, we unravel the evident influence of the valence states of the interstitial cations on their efficacy to suppress the ion migration. Incorporation of a trivalent neodymium cation (Nd3+) effectively mitigates the ion migration in the perovskite lattice with significantly reduced dosage (0.08%) compared to a widely used monovalent cation dopant (Na+, 0.45%). Less but better, the prototypical perovskite solar cells incorporated with Nd3+ exhibits significantly enhanced photovoltaic performance and operational stability.