Designing the Perovskite Structural Landscape for Efficient Blue Emission

Despite the rapid development of perovskite light-emitting diodes (PeLEDs) in recent years, blue PeLEDs' efficiencies are still inferior to those of their red and green counterparts. The poor performance is associated with, among other factors, halide segregation in bromide-chloride materials and energy funneling to lowest bandgaps in multilayered Ruddlesden-Popper (RP) systems. This study reports that compositional engineering through prudent selection of the A-site cation in a pure bromide RP system can result in a narrow distribution of layered domains. With a narrow distribution centered around the desired RP domain, efficient energy cascade to yield blue emission is ensured. Coupled with rapid nucleation induced by an antisolvent deposition technique, record efficiencies of 2.34 and 5.08%, corresponding to colorstable deep blue (similar to 465 nm) and cyan (similar to 493 nm), respectively, were attained. This composition and process engineering to design favorable structural landscape is transferrable to other material systems, which paves the way for high-performance PeLEDs.