Use of CsPbCl₃ Quantum Dots as a Chlorine Source Enables Formation of Thick Quasi‐2D Perovskite Films for High‐Performance Blue Light Emitting Diodes

Achieving efficient and stable blue-emitting quasi-two-dimensional (quasi-2D) perovskite light-emitting diodes (LEDs) remains a challenge due to the poor solubility of conventional chloride precursors and the difficulty to form thick, uniform films with a well-controlled phase distribution. A new strategy is proposed to address this challenge using CsPbCl₃ quantum dots (QDs) capped with oleylamine (OLA) ligands as an alternative chlorine source. It is demonstrated how the use of these QDs enables formation of quasi-2D perovskite films with vertically aligned crystalline structure, thickness over 100 nm, and improved stability. OLA ligands regulate the crystal phase distribution and grain boundaries, suppressing the appearance of small-n 2D phases and reducing the number of crystal defects, while inorganic CsPbCl₃ QD cores induce vertical crystallization of quasi-2D perovskite films, endowing them with enhanced structural stability. The use of this non-conventional chlorine source is proven instrumental in improving external quantum efficiency of quasi-2D perovskite sky-blue LEDs, reaching 26.2% at 485 nm, with significantly enhanced electroluminescence stability both in terms of peak position and brightness. This study demonstrates a novel methodology using CsPbCl₃ QDs capped with conventional organic ligands to achieve thick quasi-2D perovskite layers for blue LEDs, addressing existing limitations in perovskite optoelectronics.