Fig. 3: Competition of crystal growth models and suppressed nucleation by AX salts.

a, b Illustration of the 3D-like perovskites defined nucleation and growth of RP crystals from precursor solution without (a) or with (b) excessive AX additives; c influence of the AX additives (AX/PbI₂ = 0.5) on the critical concentration of precursor solution for the nucleation of PbI₂-DMF solvated phase in DMF, the error bars represent the s.d. of three measurements; d, e cross-sectional SEM images of BA-based RP perovskite films spun from precursor solution (<n> = 4) without (d) or with (e) NH₄Cl additives. The scale bar is 500 nm; f photos of BA-based RP perovskite precursor solutions (<n> = 4, 210 μL) without additive or with AX additives (AX/PbI₂ = 0.5) before the injection of chlorobenzene; g precursor solutions after injecting 540 μL CB as antisolvent, in which the precipitation of PDS was suppressed in the solutions with AX additives, as indicated by Tyndall effect.