<p>Metal halide perovskite light-emitting diodes have exhibited great potential for the next-generation displays. However, the realization of highly efficient and bright pure-blue devices with narrow emission bandwidth remains a significant challenge. Herein, we propose a controllable crystal facet growth to diminish random crystal facet-correlated defects and reveal the underlying mechanism of energy-driven facet-selective crystal growth. This strategy enables high-quality pure-blue emitters with high crystallinity, low defects, and large exciton binding energy. Consequently, we achieve highly performing pure-blue devices with a narrow emission bandwidth of 14 nm, an external quantum efficiency of 14.0% at 1699 cd m⁻², and an impressive peak brightness of 8334 cd m⁻² at an emission of 473 nm. We verify a good applicability of the strategy in achieving high-performance sky-blue devices with a narrow emission of 15 nm, a high efficiency of 23.8%, and a large luminance of 13,230 cd m^-2 at 488 nm.</p>