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.

Bilayer phosphine oxide modification toward efficient and large-area pure-blue perovskite quantum dot light-emitting diodes.

Blue emissive halide perovskite light-emitting diodes (LEDs) are gaining increasing attention. Reducing defects in halide perovskites to improve the performance of the resulting LEDs is a main research direction, but there are limited passivation methods for achieving efficient and spectrally-stable pure-blue LEDs based on mixed-halide perovskites. In this work, double modification layers containing phosphine oxides, i.e., diphenyl[4-(triphenylsilyl)phenyl]phosphine oxide (TSPO1) and 2,7-bis(diphenylphosphoryl)-9,9'-spirobifluorene (SPPO13), are developed to passivate mixed-halide perovskite quantum dot (QD) films. The comprehensive spectroscopic and structural characterization results indicate the presence of strong interactions between TSPO1/SPPO13 and the QDs. Besides, the combination of the bilayer exhibits a synergistic hole-blocking effect, improving the charge balance of the LEDs. LEDs based on the QD/TSPO1/SPPO13 films deliver stable electroluminesence at 469 nm and present a maximum external quantum efficiency (EQE) and luminance of 4.87% and 560 cd m-2, respectively. Benefiting from the uniform QD/TSPO1/SPPO13 film over a large area, LEDs with an area of 64 mm2 show a maximum EQE of 3.91%, which represents the first efficient large-area mixed-halide perovskite LED with stable pure-blue emission. This work provides a method to improve the perovskite QDs-based film quality and optoelectronic properties, and is a step toward the fabrication of highly-efficient large-area blue perovskite LEDs.

[Longitudinal analysis of endemic situation of schistosomiasis in Fu River system in Yangxin County, 2003-2012].

OBJECTIVE: To understand the endemic situation and control effect of schistosomiasis in the Fu River system in Yangxin County in recent 10 years. METHODS: The data of endemic situation and control of schistosomiasis in this area from 2003 to 2012 were collected, and the variation trends of morbidity and snail situation were analyzed longitudinally. RESULTS: Compared to 2003, the infection rates of human and cattle decreased by 97.50% and 99.44%, respectively. The total number of patients with acute schistosomiasis and advanced schistosomiasis decreased by 100% and 21.09%, respectively, and the number of schistosome infection of cattle decreased by 99.85%. Meanwhile, the Oncomelania snail area and the infection rate of snails decreased by 26.97% and 100%, respectively. CONCLUSION: Though the endemic situation of schistosomiasis in the Fu River system in Yangxin County decreased obviously year by year, the comprehensive control measures and management of floating population in this arrea should still be strengthened to prevent the endemic situation from rebounding.

[Effect of comprehensive control of schistosomiasis in Yangxin County, Hubei Province].

Since 2005, the project of comprehensive control of schistosomiasis has been implemented in Yangxin County. In 2010, the infection rates of residents and domestic animals were both below 2%, comparing to 2004, the rates decreased by 92.42% and 92.91%, respectively, and the area of susceptible zone and the infection rate of Oncomelania snails decreased by 86.25% and 84.93%, respectively. The county achieved the objective of endemic control in 2008.