Efficient Violet 3D Perovskite Light‐Emitting Diode Driven by Frenkel Excitons

ABSTRACT Using quantum confinement and mixed halides has now enabled efficient blue to near‐infrared perovskite light‐emitting diodes (PeLEDs). However, achieving highly effective violet emission using these methods is challenging due to the inefficient radiative recombination and intrinsic phase segregation. Here we report an approach for violet PeLEDs with efficient radiative recombination and excellent spectral stability, by using B‐site compositional engineering. By substituting Pb 2+ with environmentally benign Sr 2+ , we fabricate films with tunable emission covering the spectral region from 400 to 500 nm. More importantly, this approach promotes the excitons converting from Wannier‐Mott to Frenkel, known for its high exciton binding energy (E b ), which effectively accelerates the radiative recombination. The approach allows us to fabricate spectral stable violet perovskite films with photoluminescence quantum yields (PLQYs) exceeding 90% across the spectral region from 420 to 450 nm. Meanwhile, the incorporation of Sr 2+ significantly suppresses ion migration while maintaining phase stability under severe circumstances. As a result, we achieve violet PeLED with a peak external quantum efficiency (EQE) of 0.69%, ranking as one of the most efficient violet PeLED reported to date. These findings provide valuable insights for advancing the development of violet PeLEDs.