Lowering the Crystallization Energy Barrier via In Situ Heterojunction Seeding for Controlled Phase Structures in Printed Quasi-2D Perovskites

Microelectronic printing meets the demand for patterned or large-area perovskite films and, given its low cost, holds distinct advantages in industrial production. However, the crystallinity of printed perovskite films is generally relatively inferior, especially to that of spin-coated films. Under this drive, a "self-induced heterogeneous nucleation growth" scheme is developed to orchestrate the crystallization kinetics of printed quasi-2D hybrid-halide perovskite films. In this scheme, uniformly dispersed clusters with perovskite-like structures that derive from low-cost custom-built microcrystals as the crystal nucleus establish a distinct nucleation pathway that bypasses the need for both foreign particles and high energy to nucleate, directly enabling the rapid and orderly growth of printed perovskite films. This tailored crystalline growth simultaneously induces a preferentially oriented crystal phase distribution and an optimized dimensional phase arrangement, in which synergistic structural control promotes efficient carrier transport while effectively suppressing nonradiative recombination by restraining halogen segregation and defect generation during the crystallization fundamentally. Consequently, this ambient, additive-free, and scalable ink engineering motivates the establishment of a general and mature preparation framework for advancing printed perovskite optoelectronics, and the corresponding printed PEABr(MAPbI₃) films achieve a remarkable PLQY of 46.35% at 650 nm, one of the highest photoluminescence efficiencies that has been reported.