Development Of Perovskite Light-emitting Diodes Research Articles

Ca2+ induced highly fluorescent CsPb(Br/Cl)3 perovskite quantum dots via fast Anion-Exchange & Cation-Doping Inter-Promotion strategy for efficient deep-blue light-emitting diodes

Despite the impressive development of perovskite light-emitting diodes (PeLEDs), it is still challenging to achieve high-efficiency deep-blue PeLEDs using colloid perovskite quantum dots (PQDs). The efficiency of PQDs with a wavelength below 460 nm, which meets the requirements for deep-blue emission in the Telecommunication Union UHD television standard (ITU REC. 2020), lags far behind those of their sky-blue counterparts. To address this issue, a novel strategy of fast anion-exchange & cation-doping inter-promotion (FAECDIP) is proposed to achieve highly efficient deep-blue PQDs by introducing CaBr2 into the CsPbCl3 PQDs. Owing to the presence of Ca2+, the speed of ion exchange is increased, driven by the smaller cation, Ca2+, improving the preparation efficiency. Additionally, Ca2+ was doped on the surface of PQDs. Based on studies of fast anion-exchange and theoretical calculations, Ca2+ improves the optical performance by decreasing the number of traps and increasing the crystallinity of target PQDs, facilitating the stability of treated films and PeLEDs by enhancing the formation energy of halogen vacancies. Here, a high PLQY of 80.3 % CaBr2-induced CsPb(Cl/Br)3 deep-blue PQDs (∼446 nm) was achieved. The correspondent PeLEDs (∼447 nm) achieved a superior EQE of 5.88 %, which is the state-of-the-art among the reported deep-blue PeLEDs. Our strategy provides a potential route to achieve deep-blue PeLEDs, which differs from the previous tedious-complex methods.

Advancements in the Improvement of Optical Outcoupling Efficiency for Perovskite LEDs

In the past 10 years, the development of perovskite light-emitting diodes (PeLEDs) was fast. Due to the excellent properties of high brightness and color purity, multiple color emission, and cost-effective fabrication technology, PeLEDs have been very promising in semiconductor lighting and display applications. In an effort to achieve high-efficient PeLED devices, researchers have devoted themselves to explore and optimize the emitted materials and device structures. Among various research approaches, raising the optical outcoupling efficiency ( η out ) of PeLED through light management strategies is very important for further promoting device performances, which is due to that approximately 80% of the photons generated internally are captured or worn out in different optical modes in the device. In this review, the latest researches on optical outcoupling regulations in PeLED are outlined, which mainly focus on photophysical properties and implementation methods. As the key part of this review, implementation strategies are classified into the optimization of characteristics of functional materials (refractive index, film thickness, anisotropy, and photon recovery) and adjustment of device architecture (patterned nanostructures, photonic crystals, metal nanostructures, and external couplers). Additionally, a prospect of the future directions and development trend for this research field is presented in order to achieve ultra-efficient PeLED and future commercial applications.

Perovskite light-emitting diodes

Light-emitting diodes based on halide perovskites have undergone rapid development in recent years and can now offer external quantum efficiencies of over 23%. However, the practical application of such devices is still limited by a number of factors, including the poor efficiency of blue-emitting devices, difficulty in accessing emission wavelengths above 800 nm, a decrease in external quantum efficiency at high current density, a lack of understanding of the effect of the electric field on mobile ions present in the perovskite materials, and short device lifetimes. Here we review the development of perovskite light-emitting diodes. We examine the key challenges involved in creating efficient and stable devices, and consider methods to alleviate the poor efficiency of blue-emitting devices, leverage emission in the long infrared region and create spin-polarized light-emitting diodes. This Review examines the development of perovskite light-emitting diodes, exploring the key challenges involved in creating efficient and stable devices.

High brightness and stability pure-blue perovskite light-emitting diodes based on a novel structural quantum-dot film

The further development of perovskite light-emitting diodes (PeLEDs) is severely retarded by poor stability and low brightness of pure-blue emission in the range of 460–470 nm wavelength. Here, we devise a novel structure sandwich panel (SWP) of perovskite quantum dot (QD) film to modulate charge recombination, in which this structure is the first time to be used in LEDs. The SWP film is constructed by inserting a ZnCl2 ultrathin interlayer into the middle of pure-blue emitting (460 nm wavelength) CsPbBr3 QD film. The charge recombination zone is completely limited within the SWP film by the interlayer to alleviate the accumulation of carriers at interfaces of the QD film and hole transport layer, thus reducing the interfacial exciton quenching and Auger recombination. The PeLEDs based on SWP film show stabilized pure-blue emitting at 469 nm and external quantum efficiency (EQE) of 5% that shows low roll-off and maintains over 90% of the initial value at high luminance 10,000 cd m−2. The maximum luminance of the device is up to 10,410 cd m−2, which is the highest value for pure-blue PeLED reported, meeting the requirement of brightness in pixel for the augmented displays. The operational half-lifetime under continuous operation at the initial luminance of 100 cd m−2 is 59 h, which is the best operational stability for the known blue PeLEDs.

Enhanced performance of spectra stable blue perovskite light-emitting diodes through Poly(9-vinylcarbazole) interlayer incorporation

Since the emergence of organic-inorganic hybrid perovskites, the development of perovskite light-emitting diodes (PeLEDs) with green/red emission have made great progress, and the corresponding external quantum efficiency (EQE) has exceeded 20%. However, the research progress of blue-emitting PeLED still has certain challenges. In this article, a multi-cation per-bromine perovskite film is prepared by introducing polymer molecules poly(9-vinylcarbazole) (PVK) in an anti-solvent (chloroform). When the concentration of PVK is optimized to 0.1 mg/mL, a smooth, dense, high-quality film with photoluminescence quantum efficiency (PLQY) up to 20.70% is obtained. The introduction of PVK can assist the formation of perovskite films for interface modification via surface defect passivation. The optimized blue PeLED has a maximum brightness of 3136 cd/m2 and a maximum EQE of 3.49% at 488 nm. More importantly, the optimized blue PeLED has excellent color stability under high applied voltage up to 12 V or continuous operation.

Effect of chloride Ion concentrations on luminescence peak blue shift of light-emitting diode using anti-solvent extraction of quasi-two-dimensional perovskite

In recent years, Perovskite Light-Emitting Diodes (PeLEDs) have received considerable attention in academia. However, with the development of PeLEDs, commercial applications of full-color PeLED technology are largely limited by the progress of blue-emitting devices, due to the uncontrollably accurate composition, unstable properties, and low luminance. In this article, we add Cesium chloride (CsCl) to the quasi-two-dimensional (quasi-2D) perovskite precursor solution and achieve the relatively blue shifts of PeLED emission peak by introducing chloride ions for photoluminescence (PL) and electroluminescence (EL). We also found that the introduction of chlorine ions can make quasi-2D perovskite films thinner with smoother surface of 0.408 nm. It is interesting that the EL peaks and intensities of PeLED are adjustable under different driving voltages in high concentration chlorine-added perovskite devices, and different processes of photo-excited, photo-quenched, and photo-excited occur sequentially with the increasing driving voltage. Our work provides a path for demonstrating full-color screens in the future.

Metal halide perovskites for light-emitting diodes

Metal halide perovskites have shown promising optoelectronic properties suitable for light-emitting applications. The development of perovskite light-emitting diodes (PeLEDs) has progressed rapidly over the past several years, reaching high external quantum efficiencies of over 20%. In this Review, we focus on the key requirements for high-performance PeLEDs, highlight recent advances on materials and devices, and emphasize the importance of reliable characterization of PeLEDs. We discuss possible approaches to improve the performance of blue and red PeLEDs, increase the long-term operational stability and reduce toxicity hazards. We also provide an overview of the application space made possible by recent developments in high-efficiency PeLEDs.

Designing the Perovskite Structural Landscape for Efficient Blue Emission

Despite the rapid development of perovskite light-emitting diodes (PeLEDs) in recent years, blue PeLEDs’ efficiencies are still inferior to those of their red and green counterparts. The poor perfo...

Modulation of recombination zone position for quasi-two-dimensional blue perovskite light-emitting diodes with efficiency exceeding 5%

In recent years, substantial progress has been made in developing perovskite light-emitting diodes with near-infrared, red and green emissions and over 20% external quantum efficiency. However, the development of perovskite light-emitting diodes with blue emission remains a great challenge, which retards further development of full-color displays and white-light illumination based on perovskite emissive materials. Here, firstly, through composition and dimensional engineering, we prepare quasi-two-dimensional perovskite thin films with improved blue emission, taking advantages of reduced trap density and enhanced photoluminescence quantum yield. Secondly, we find a vertically non-uniform distribution of perovskite crystals in the PEDOT:PSS/perovskite hybrid film. Through modulating the position of the recombination zone, we activate the majority of quasi-two-dimensional perovskite crystals, and thus demonstrate the most efficient blue perovskite light-emitting diode to date with emission peak at 480 nm, record luminance of 3780 cd m−2 and record external quantum efficiency of 5.7%.

Boosted electroluminescence of perovskite light-emitting diodes by pinhole passivation with insulating polymer

Organic–inorganic hybrid perovskites are emerging as promising light-emitting materials due to their superior photophysical properties. Poor surface coverage creating substantial pinholes and shunt paths, nevertheless, is one of the most severe problems that hinder the further development of perovskite light-emitting diodes (PeLEDs). Here in this work, we demonstrated a fabrication of PeLEDs by using a robust, stable, and highly transparent poly(methyl methacrylate) (PMMA) polymer to passivate the pinholes of CH3NH3PbBr3 emissive layer and hence reduce the non-radiative losses through the shunt paths formed by the pinholes. Uniform surface coverage and reduced leakage current were achieved. Green electroluminescence (EL) emission centered at ~534 nm was greatly boosted by a factor of 10 at 8 V with optimizing the thickness of the PMMA modifier. This facile and universal technique provides an effective way to circumvent the poor formation of the CH3NH3PbBr3 perovskite film and may be very helpful in the development of PeLEDs.

Quasi‐2D Inorganic CsPbBr3 Perovskite for Efficient and Stable Light‐Emitting Diodes

AbstractMetal halide perovskites are rising as a competitive material for next‐generation light‐emitting diodes (LEDs). However, the development of perovskite LEDs is impeded by their fast carriers diffusion and poor stability in bias condition. Herein, quasi‐2D CsPbBr3 quantum wells homogeneously surrounded by inorganic crystalline Cs4PbBr6 of large bandgap are grown. The centralization of carriers in nanoregion facilitates radiative recombination and brings much enhanced luminescence quantum yield. The external quantum efficiency and luminescence intensity of the LEDs based on this nanocomposite are one order of magnitude higher than the conventional low‐dimensional perovskite. Meanwhile, the use of inorganic nanocomposite materials brings much improved device operation lifetime under constant electrical field.