All-Solution-Processed Perovskite Light-Emitting Diodes Based on a Thiol-Modified ZnO Electron-Transporting Layer

Metal Halide Perovskite LEDs for Visible Light Communication and Lasing Applications

Metal halide perovskites, known for their pure and tunable light emission, near-unity photoluminescence quantum yields, favorable charge transport properties, and excellent solution processability, have emerged as promising materials for large-area, high-performance light-emitting diodes (LEDs). Over the past decade, significant advancements have been made in enhancing the efficiency, response speed, and operational stability of perovskite LEDs. These promising developments pave the way for a broad spectrum of applications extending beyond traditional solid-state lighting and displays to include visible light communication (VLC) and lasing applications. This perspective evaluates the current state of perovskite LEDs in those emerging areas, addresses the primary challenges currently impeding the development of perovskite-based VLC systems and laser diodes, and provides an optimistic outlook on the future realization of perovskite-based VLC and electrically pumped perovskite lasers.

Synthesis and Characterization of a Semiconductor Diodic Bilayer PbS/CdS Made by the Chemical Bath Deposition Technique

In this work, we report a heterojunction formed by a PbS/CdS bilayer using the chemical bath deposition (CBD) technique because it is a relatively simple, fast, and low-cost technique; is permitted to obtain high-quality thin films (TFs); and also covers large areas. Some characterizations have been carried out to confirm the identity of the involved bilayer. For the cadmium sulfide (CdS) film, optical properties such as absorption, transmission, reflection, extinction coefficient, and refractive index were measured. Moreover, the bandgap was calculated, and morphology was obtained by scanning electron microscopy (SEM). Also, X-ray diffraction (XRD) and high-resolution transmission electron microscopy (TEM) were performed for the synthesis of CdS films. On the other hand, for the synthesis of lead sulfide (PbS) films, we performed TEM, energy-dispersive spectroscopy, and XRD. A surface morphological SEM image of the PbS film synthesized was also taken. The multiheterojunction PbS/CdS bilayer was characterized by the current-voltage (I-V) curve, and the behavior of the bilayer was evaluated under the conditions of darkness and controlled fixed lighting, detecting a very slight photosensitivity of the complete diodic device through those measurements. The calculated bandgap for the CdS TF was E g = 2.55 eV, while after a chosen thermal annealing, the bandgap decreased to 2.38 eV. On the other hand, the PbS film presented a cubic structure.

Enhanced performance of quantum dot light-emitting diodes enabled by zirconium doped SnO2 as electron transport layers

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 100567 cd·m-2 luminance, 14.3% maximum external quantum efficiency, and 13.1 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.

High-Performance All-Inorganic Architecture Perovskite Light-Emitting Diodes Based on Tens-of-Nanometers-Sized CsPbBr3 Emitters in a Carrier-Confined Heterostructure

Developing green perovskite light-emitting diodes (PeLEDs) with a high external quantum efficiency (EQE) and low efficiency roll-off at high brightness remains a critical challenge. Nanostructured emitter-based devices have shown high efficiency but restricted ascending luminance at high current densities, while devices based on large-sized crystals exhibit low efficiency roll-off but face great challenges to high efficiency. Herein, we develop an all-inorganic device architecture combined with utilizing tens-of-nanometers-sized CsPbBr3 (TNS-CsPbBr3) emitters in a carrier-confined heterostructure to realize green PeLEDs that exhibit high EQEs and low efficiency roll-off. A typical type-I heterojunction containing TNS-CsPbBr3 crystals and wide-bandgap Cs4PbBr6 within a grain is formed by carefully controlling the precursor ratio. These heterostructured TNS-CsPbBr3 emitters simultaneously enhance carrier confinement and retain low Auger recombination under a large injected carrier density. Benefiting from a simple device architecture consisting of an emissive layer and an oxide electron-transporting layer, the PeLEDs exhibit a sub-bandgap turn-on voltage of 2.0 V and steeply rising luminance. In consequence, we achieved green PeLEDs demonstrating a peak EQE of 17.0% at the brightness of 36,000 cd m-2, and the EQE remained at 15.7% and 12.6% at the brightness of 100,000 and 200,000 cd m-2, respectively. In addition, our results underscore the role of interface degradation during device operation as a factor in device failure.