We demonstrate efficient, stable, and fully RoHS-compliant near-infrared (NIR) light-emitting diodes (LEDs) based on InAs/ZnSe quantum dots (QDs) synthesized by employing a commercially available amino-As precursor. They have a record external quantum efficiency of 5.5% at 947 nm and an operational lifetime of ∼32 h before reaching 50% of their initial luminance. Our findings offer a new solution for developing RoHS-compliant light-emitting technologies based on Pb-free colloidal QDs.

https://pubs.acs.org/doi/pdf/10.1021/acsenergylett.2c02070

Near-Infrared Light-Emitting Diodes Based on RoHS-Compliant InAs/ZnSe Colloidal Quantum Dots

Highly bright and stable single-crystal perovskite light-emitting diodes

Perovskite light-emitting diodes (LEDs) have attracted broad attention due to their rapidly increasing external quantum efficiencies (EQEs)1-15. However, most high EQEs of perovskite LEDs are reported at low current densities (<1 mA cm-2) and low brightness. Decrease in efficiency and rapid degradation at high brightness inhibit their practical applications. Here, we demonstrate perovskite LEDs with exceptional performance at high brightness, achieved by the introduction of a multifunctional molecule that simultaneously removes non-radiative regions in the perovskite films and suppresses luminescence quenching of perovskites at the interface with charge-transport layers. The resulting LEDs emit near-infrared light at 800 nm, show a peak EQE of 23.8% at 33 mA cm-2 and retain EQEs more than 10% at high current densities of up to 1,000 mA cm-2. In pulsed operation, they retain EQE of 16% at an ultrahigh current density of 4,000 mA cm-2, along with a high radiance of more than 3,200 W s-1 m-2. Notably, an operational half-lifetime of 32 h at an initial radiance of 107 W s-1 m-2 has been achieved, representing the best stability for perovskite LEDs having EQEs exceeding 20% at high brightness levels. The demonstration of efficient and stable perovskite LEDs at high brightness is an important step towards commercialization and opens up new opportunities beyond conventional LED technologies, such as perovskite electrically pumped lasers. 

https://www.repository.cam.ac.uk/bitstream/1810/348319/3/198.pdf

Bright and stable perovskite light-emitting diodes in the near-infrared range

Quasi‐2D Ruddlesden‐Popper perovskites receive tremendous attention for application in light‐emitting diodes (LEDs). However, the role of organic ammonium spacers on perovskite film has not been fully‐understood. Herein, a spacer cation assisted perovskite nucleation and growth strategy, where guanidinium (GA+) spacer is introduced into the perovskite precursor and at the interface between the hole transport layer (HTL) and the perovskite, to achieve dense and uniform perovskite films with enhanced optical and electrical performance is developed. A thin GABr interface pre‐formed on HTL provides more nucleation sites for perovskite crystal; while the added GA+ in perovskite reduces the crystallization rate due to strong hydrogen bonding interacts with intermediates, which promotes the growth of enhanced‐quality quasi‐2D perovskite films. The ionized ammonium group (NH3+) of GA+ also favors formation of polydisperse domain distribution, and amine or imine (NH2 or NH) group interact with perovskite defects through coordination bonding. The spacer cation assisted nucleation and growth strategy is advantageous for producing efficient and high‐luminance perovskite LEDs, with a peak external quantum efficiency of over 20% and a luminance up to 100 000 cd m−2. This work can inform and underpin future development of high‐performance perovskite LEDs with concurrent high efficiency and brightness.

/pdf/a-spacer-cation-assisted-nucleation-and-growth-strategy-2kbpc9am.pdf

A Spacer Cation Assisted Nucleation and Growth Strategy Enables Efficient and High‐Luminance Quasi‐2D Perovskite LEDs

Zero‐dimensional (0D) organic metal halide hybrids (OMHHs) have recently emerged as a new class of light emitting materials with exceptional color tunability. While near‐unity photoluminescence quantum efficiencies (PLQEs) are routinely obtained for a large number of 0D OMHHs, it remains challenging to apply them as emitter for electrically driven light emitting diodes (LEDs), largely due to the low conductivity of wide bandgap organic cations. Here, the development of a new OMHH, triphenyl(9‐phenyl‐9H‐carbazol‐3‐yl) phosphonium antimony bromide (TPPcarzSbBr4), as emitter for efficient LEDs, which consists of semiconducting organic cations (TPPcarz+) and light emitting antimony bromide anions (Sb2Br82−), is reported. By replacing one of the phenyl groups in a well‐known tetraphenylphosphonium cation (TPP+) with an electroactive phenylcarbazole group, a semiconducting TPPcarz+ cation is developed for the preparation of red emitting 0D TPPcarzSbBr4 single crystals with a high PLQE of 93.8%. With solution processed TPPcarzSbBr4 thin films (PLQE of 86.1%) as light emitting layer, red LEDs are fabricated to exhibit an external quantum efficiency (EQE) of 5.12%, a peak luminance of 5957 cd m−2, and a current efficiency of 14.2 cd A−1, which are the best values reported to date for electroluminescence devices based on 0D OMHHs.

Efficient Red Light Emitting Diodes Based on a Zero‐Dimensional Organic Antimony Halide Hybrid

Perovskite light-emitting diodes are an emerging light source technology. However, similar to perovskite solar cells, poor operational stability remains an obstacle for commercial applications. Here we demonstrate ultrastable and efficient near-infrared (~800 nm) perovskite light-emitting diodes with record-long operational lifetimes (T50, extrapolated) of 11,539 h (~1.3 years) and 32,675 h (~3.7 years) for initial radiance (or current densities) of 3.7 W sr−1 m−2 (~5.0 mA cm−2) and 2.1 W sr−1 m−2 (~3.2 mA cm−2), respectively, with even longer lifetimes forecasted for lower radiance. Key to this stability is the introduction of a dipolar molecular stabilizer, which interacts with the cations and anions at the perovskite grain boundaries. This suppresses ion migration under electric fields, preventing the formation of lead iodide, which mediates the phase transformation and decomposition of α-FAPbI3 perovskite. These results remove the critical concern that halide perovskite devices may be intrinsically unstable, paving the path towards industrial applications. Near-infrared perovskite light-emitting diodes with extrapolated device lifespans on the scale of years are achieved by the use of a dipolar molecular stabilizer. 

/pdf/efficient-and-ultra-stable-perovskite-light-emitting-diodes-774nyao6.pdf

Efficient and ultra-stable perovskite light-emitting diodes

/pdf/ultrastable-near-infrared-perovskite-light-emitting-diodes-2x5ct5k6.pdf

Ultrastable near-infrared perovskite light-emitting diodes

Instability caused by the migrating ions is one of the major obstacles toward the large-scale application of metal halide perovskite optoelectronics. Inactivating mobile ions/defects via chemical passivation, e.g., amino acid treatment, is a widely accepted approach to solve that problem. To investigate the detailed interplay, L-phenylalanine (PAA), a typical amino acid, is used to modify the SnO2/MAPbI3 interface. The champion device with PAA treatment maintains 80% of its initial power conversion efficiency (PCE) when stored after 528 h in an ambient condition with the relative humidity exceeding 70%. By employing a wide-field photoluminescence imaging microscope to visualize the ion movement and calculate ionic mobility quantitatively, we propose a model for enhanced stability in perspective of suppressed ion migration. Besides, we reveal that the PAA dipole layer facilitates charge transfer at the interface, enhancing the PCE of devices. Our work may provide an in-depth understanding toward high-efficiency and stable perovskite optoelectronic devices.

Manipulating Ion Migration and Interfacial Carrier Dynamics via Amino Acid Treatment in Planar Perovskite Solar Cells.

The effective utilization of wave energy is one of the important means to solve the shortage ofresources. The dual hydraulic PTO floating system (floating system hereinafter), is an important device for converting wave energy. The system is mainly composed of an energy extraction system (PTO system), float, and vibrator. Under the action of wave energy, the floater and vibrator of the floating body system move relatively, which drives the PTO system to generate electricity. Many researchers have studied the motion characteristics ofa floating body system in a heave state and calculated the energy conversion characteristics accordingly. In practice, the floating body system heaves and pitches due to wave energy. We propose an improved motion simulation algorithm for the Double Floating Body System based on the original researchers. The improved motion simulation algorithm adds the floating body’s pitch motion state, considers the floating body’s motion under both heave and pitch, and further analyzes the power conversion characteristics based on the motion characteristics.

Analysis and Research of Moving Simulation Improvement Algorithms Based on Two-body Floating System


 
 
 
Purpose: To investigate the protective effect of Crataegus songarica extract (CSCE) against traumatic brain injury (TBI) in rats, and the underlying mechanism of action. 
Methods: A rat model of TBI was established via tracheal intubation procedure, and the rats were treated with graded doses of CSCE. Neuronal survival was determined by Nissl staining, while neuronal apoptosis was measured using TUNEL-staining. Neurological impairments were determined based on neurological severity score (NSS). 
Results: Treatment of TBI rats with CSCE enhanced neuronal survival and decreased TUNEL-positive cell fraction in the brain cortex. The treatment prevented elevation of NSS and suppressed mRNA and protein expression levels of IL-6 and TNF-α in brain cortex. Moreover, CSCE treatment prevented TBI-mediated suppression of activities of superoxide dismutase (SOD) and glutathione peroxidase (GPx), and attenuated hydrogen peroxide (H2O2) levels in TBI rat brain cortex. Treatment of TBI rats with CSCE down-regulated NF-κB expression, increased Nrf2 expression and up-regulated mRNA expressions of heme oxygenase 1 (HO-1) and quinine oxidoreductase 1 (NQO-1). 
Conclusion: These results suggest that CSCE prevents TBI-mediated reduction in neuronal survival and inhibits brain cortical neuronal death in rats. It improves NSS and inhibits inflammatory response via activation of Nrf2 pathway and targeting of NF-κB expression. Therefore, CSCE is a potential therapeutic agent for TBI. 
 
 
 


Puyang Li

Papers

Efficient and ultra-stable perovskite light-emitting diodes

Ultrastable near-infrared perovskite light-emitting diodes

Manipulating Ion Migration and Interfacial Carrier Dynamics via Amino Acid Treatment in Planar Perovskite Solar Cells.

Analysis and Research of Moving Simulation Improvement Algorithms Based on Two-body Floating System

Neuroprotective effects of crude extract of Crataegus songarica on a rat model of traumatic brain injury