Imidazole additives in 2D halide perovskites: impacts of –CN versus –CH3 substituents reveal the mediation of crystal growth by phase buffering

A cyano-based DCI additive induces phase-buffering during the crystallization growth process of 2D halide perovskites, which effectively suppresses interphase strain, enhances lattice orientation and reduces trap-state density, delivering an outstanding and stable efficiency of ∼17.0% (n = 4).