Two‐Dimensional Cs₂AgIn_xBi_1‐xCl₆ Alloyed Double Perovskite Nanoplatelets for Solution‐Processed Light‐Emitting Diodes

Abstract

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, the first synthesis of 2D Cs2AgInxBi1‐xCl6 (0 ≤ x ≤ 1) alloyed double perovskite nanoplatelets (NPLs) with well controlled morphology and composition is demonstrated. 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. The first solution‐processed light‐emitting diodes is demonstrated using the Cs2AgIn0.9Bi0.1Cl6 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−1. This 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.

K-Alloyed Lead-free Double-Perovskite Cs2AgBiBr6 Nanocrystals for Use in Light-Emitting Diodes

“…Furthermore, temperature-dependent PL measurements were carried out for Cs 2 AgBiBr 6 NCs and Cs 2 Ag 0.64 K 0.36 BiBr 6 NCs in the temperature range of 80–300 K (Figure a–d). The PL intensity gradually decreased with increasing temperature, which was attributed to the thermally activated nonradiative recombination. , In order to extract the exciton binding energy ( E b ), the normalized PL intensity as a function of temperature for NCs was plotted (Figure e). The relationship between intensity and temperature was fitted using Arrhenius eq , , I ( T ) = I 0 1 + A e − E normalb / K b T where I ( T ) and I 0 are the PL intensities at temperatures T and 0 K, respectively.…”

“…The PL intensity gradually decreased with increasing temperature, which was attributed to the thermally activated nonradiative recombination. , In order to extract the exciton binding energy ( E b ), the normalized PL intensity as a function of temperature for NCs was plotted (Figure e). The relationship between intensity and temperature was fitted using Arrhenius eq , , I ( T ) = I 0 1 + A e − E normalb / K b T where I ( T ) and I 0 are the PL intensities at temperatures T and 0 K, respectively. A is the fitting constant, E b is the exciton binding energy, and k b is the Boltzmann constant.…”

“…The stability of optoelectronic materials is critical for their practical applications . To assess the stability of Cs 2 AgBiBr 6 and Cs 2 Ag 0.64 K 0.36 BiBr 6 NCs, we monitored their stability in toluene solution for optical properties over a period of 20 days (Figure S3).…”

“…The PL intensity gradually decreased with increasing temperature, which was attributed to the thermally activated nonradiative recombination. 42,43 In order to extract the exciton binding energy (E b ), the normalized PL intensity as a function of temperature for NCs was plotted (Figure 7e). The relationship between intensity and temperature was fitted using Arrhenius eq 3, 43,44 = +…”

“…42,43 In order to extract the exciton binding energy (E b ), the normalized PL intensity as a function of temperature for NCs was plotted (Figure 7e). The relationship between intensity and temperature was fitted using Arrhenius eq 3, 43,44 = +…”