ABSTRACT
Next-generation display and lighting based on quantum dot light-emitting diodes (QLEDs) require a balanced electron injection of electron transport layers (ETLs). However, classical ZnO nanoparticles (NPs) as ETLs face inherent defects such as excessive electron injection and positive aging effects, urgently requiring the development of new types of ETL materials. Here, we show that high stability SnO2 NPs as ETL can significantly improve the QLED performance to 100567â cd·m-2 luminance, 14.3% maximum external quantum efficiency, and 13.1â cd·A-1 maximum current efficiency using traditional device structures after optimizing the film thickness and annealing the temperature. Furthermore, experimental tests reveal that by doping Zr4+ ions, the size of SnO2 NPs will reduce, dispersion will improve, and energy level will shift up. As expected, when using Zr-SnO2 NPs as the ETL, the maximum external quantum efficiency can reach 16.6%, which is close to the state-of-the-art QLEDs based on ZnO ETL. This work opens the door for developing novel, to the best of our knowledge, type ETLs for QLEDs.
ABSTRACT
CuInS2 (CIS) quantum dots (QDs) represent an important class of colloidal materials with broad application potential, owing to their low toxicity and unique optical properties. Although coating with a ZnS shell has been identified as a crucial method to enhance optical performance, the occurrence of cation exchange has historically resulted in the unintended formation of Cu-In-Zn-S alloyed QDs, causing detrimental blueshifts in both absorption and photoluminescence (PL) spectral profiles. In this study, we present a facile one-pot synthetic strategy aimed at impeding the cation exchange process and promoting ZnS shell growth on CIS core QDs. The suppression of both electron-phonon interaction and Auger recombination by the rigid ZnS shell results in CIS/ZnS core/shell QDs that exhibit a wide near-infrared (NIR) emission coverage and a remarkable PL quantum yield of 92.1%. This effect boosts the fabrication of high-performance, QD-based NIR light-emitting diodes with the best stability of such materials so far.
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 Cs2 AgInx Bi1- x Cl6 (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 Cs2 AgIn0.9 Bi0.1 Cl6 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.
