Enhancing Efficiencyand Stability of Blue PerovskiteLight-Emitting Diodes through Hybrid A‑Site Optimization andDefect Mitigation in Pure Bromide-Based Materials

Blue perovskite light-emitting diodes (PeLEDs) have garnered significant attention for their potential in full-color electronic displays. However, issues like the formation of low-dimensional phases and defects in the perovskite emissive layer hinder their performance, leading to multiple electroluminescence (EL) peaks and increased nonradiative recombination, which limit efficiency and brightness. In this study, we demonstrate the fabrication of high-efficiency, pure-bromide-based quasi-two-dimensional (Q-2D) PeLEDs using a dual-strategy approach. By introducing CsBr into the PBABr_1.2(FAPbBr₃) system, we effectively suppress low-dimensional phase formation, resulting in devices with a single EL peak. Moreover, incorporating tetraisopropyl methylenediphosphonate (TMPP) during antisolvent treatment not only prevents the emergence of low-dimensional phases but also passivates under-coordinated Pb²⁺ defects in the perovskite layer. Detailed characterizations reveal that TMPP interacts specifically with Pb²⁺ defects, optimizing charge carrier dynamics and enhancing energy transfer efficiency. The resulting PeLEDs exhibit a maximum brightness of 678 cd/m² and a peak external quantum efficiency (EQE) of 7.30%. Compared to conventional devices, the TMPP-doped, antisolvent-treated PeLEDs show a remarkable improvement, with efficiency and brightness increasing by over 118% and 230%, respectively. This work highlights the effectiveness of defect passivation through antisolvent doping, providing valuable insights for enhancing the performance of pure-bromide-based blue PeLEDs and advancing next-generation optoelectronic devices.