Metal-halide perovskites are an emerging class of semiconductors with outstanding optoelectronic properties, facile solution processability, and tunable bandgaps, making them highly attractive for solar cells, lasers, photodetectors, and light-emitting diodes (LEDs). Among these, perovskite LEDs (PeLEDs) are highly promising candidates for next-generation displays and solid-state lighting due to their high color purity. However, while green and red PeLEDs have achieved remarkable progress in efficiency and stability, blue PeLEDs remain a critical challenge. Current devices suffer from poor operational lifetimes, electroluminescence instability under bias, and efficiency losses associated with unbalanced charge injection and non-radiative recombination pathways.

Previous studies have reported that the trap density in blue 3D perovskites can be significantly reduced by introducing a B-site alloy (Pb/Sr), resulting in improved color stability and enhanced efficiency of LEDs. In this study, we propose a dual strategy to address the limitations. First, substituting Pb²⁺ with strontium ions in quasi-2D perovskites aims to reduce trap density in blue perovskite LEDs. Moreover, introducing small amounts of Sr²⁺ has a minimal impact on the crystal structure due to its similar ionic radius to Pb²⁺, while promoting the formation of continuous and denser perovskite films with fewer defects. This leads to an enhanced photoluminescence quantum yield, longer photoluminescence lifetimes and improved spectral stability of blue perovskite films. Second, we incorporate (2-(3,6-dibromo-9H-carbazol-9-yl)ethyl)phosphonic acid, a carbazole-based molecule with a deep HOMO level, into the precursor solution. This additive facilitates balanced hole injection and passivates trap states, thereby suppressing non-radiative recombination and offering a viable strategy for enhancing the performance of blue perovskite LEDs. The combination of Sr²⁺ substitution and carbazole-based additive engineering yields blue perovskite LEDs with improved efficiency, stability, and emission quality. These findings provide valuable insights into material design and device engineering strategies, advancing the development of reliable blue PeLEDs for future display and lighting technologies.

Keywords: metal-halide perovskites, blue emission, Sr²⁺ doping, carbazole-based additive, PeLEDs.