Two-Dimensional Cs 2 AgIn x Bi 1-x Cl 6 Alloyed Double Perovskite Nanoplatelets for Solution-Processed Light-Emitting Diodes.

Lead-free double perovskites have emerged as a promising class of materials with potential to be integrated into a wide range of optical and optoelectronic applications. Herein, we demonstrate the first synthesis of two-dimensional (2D) Cs 2 AgIn x Bi 1-x Cl 6 (0 ≤ x ≤ 1) alloyed double perovskite nanoplatelets (NPLs) with well controlled morphology and composition. The obtained NPLs show unique optical properties with the highest photoluminescence quantum yield of 40.1%. Both temperature dependent spectroscopic studies and density functional theory calculation results reveal that the morphological dimension reduction and In-Bi alloying effect together boost the radiative pathway of the self-trapped excitons of the alloyed double perovskite NPLs. Moreover, the NPLs exhibit good stability under ambient conditions and against polar solvents, which is ideal for all solution-processing of the materials in low-cost device manufacturing. We demonstrate the first solution-processed light-emitting diodes using the Cs 2 AgIn 0.9 Bi 0.1 Cl 6 alloyed double perovskite NPLs as the sole emitting component, showing luminance maximum of 58 cd/m 2 and peak current efficiency of 0.013 cd/A. Our study sheds light on morphological control and composition-property relationships of double perovskite nanocrystals, paving the way toward ultimate utilizations of lead-free perovskite materials in diverse sets of real-life applications. This article is protected by copyright. All rights reserved.