Realization of high-performance blue organic light-emitting diodes using multi-emissive layers

High-performance blue organic light-emitting diodes （OLEDs） are developed. A concept of using multiple-emissive layer （EML） configuration is adopted. In this letter, bis（2-methyl-8-quinolinolate）-4- （phenylphenolato）A1 （BAlq） and 9,10-di（naphtha-2-yl）anthracene （ADN）, which serve n- and p-type EMLs, respectively, are used to evaluate and demonstrate the multi-EML concept for blue OLEDs. The thickness effect of individual EMLs and the number of EMLs, e.g., triple and quadruple EML components, on the power efficiency of blue OLEDs are systematically investigated. To illustrate the point, the total thickness of the emissive region in different blue OLEDs are kept contact at 30 nm for comparison. The power efficiency of blue OLEDs with a quadruple EML structure of BAlq/ADN/BAlq/ADN is about 40% higher than that of blue OLEDs having a single EML unit. The Commission Internationale deL＇eclairage color coordinates of multi-EML OLEDs have values that represent the average of blue emissions from individual EMLs of BAlq and ADN.

Discovery of Single-Atom Catalyst:Customized Heteroelement Dopants on Graphene

CONSPECTUS:Single-atomic catalyst(SAC)incorporated in graphene plays an increasingly significant role in many applications,including sustainable energy conversion/storage and environmental systems.Such a synergistic structure commonly consisting of atomic metal active sites stabilized on a robust graphene support,is breaking through the intrinsic limitations of precious-metalbased catalysts and broadening a spectrum of applications,while attaining high atom utilization,remarkable novel catalytic activity,and conformational flexibility.Motivated from the unprecedented attractive features of SAC in graphene,enormous research efforts have been devoted to the development of this ultimate catalytic system.For the further advance and eventual success in this field,a general rule for the rational design of SAC is the first prerequisite.Unfortunately,the research effort for the exploration of the fundamental reaction mechanism and rational design principle has been frequently overlooked in spite of the significantly accumulated research efforts thus far.In this Account,we highlight a new perspective for the rational design of SAC in graphene,conceptually centered on the atomistic level heteroelement dopants of graphene.To provide the intuitive viewpoint on the SAC from the scientific perspective,we suggest a new classification scheme for versatile SACs reported thus far into“dopant catalyst”and“dopant-assisted catalyst”,based on the detailed role of dopant in the catalyst system.Thereafter,we highlight the crucial influencing factors on the catalytic activity of the dopant-induced-catalyst system and toward rational designing rule for high performance catalysts.The recent progress in the dopantinduced-catalyst system for a wide spectrum of catalytic applications,including oxygen reduction,oxygen evolution,hydrogen evolution,and CO_(2)reduction is summarized.Finally,we briefly discuss the challenges and opportunities for the future research direction.The exciting expectation for the well-defined,specifically tailored,high performance dopant-induced-catalyst system is anticipated to address global challenges,including climate change,energy crisis and worldwide pandemics.

Solution processed high performance perovskite quantum dots/ZnO phototransistors

Phototransistors that can detect visible light have been fabricated using solution processed zinc oxide channel/zirconium oxide gate insulator thin film transistors(TFTs)and room temperature synthesized perovskite quantum dots(PeQDs)as active layer.Typical ZnO thin film transistors did not show a photocurrent under visible light illumination.However,ZnO TFTs decorated with PeQDs exhibited enhanced photocurrent upon exposure to visible light.The device had a responsivity of 567 A/W(617 A/W),a high detectivity of 6.59×10^(13)Jones(1.85×10^(14)J)and a high sensitivity of 10^(7)(10^(8))under green(blue)light at a low drain voltage of 0.1 V.The high photo-responsivity and detectivity under green light resulted from the combination of short ligands in the QDs films and the high mobility of the spray coated ZnO films.Those results are relevant for the development of low cost and low energy consumption phototransistors working in the visible range.