A lithium-oxygen battery would deliver the highest energy density of a rechargeable battery, but the multiphase electrochemical reaction on the air cathode has difficulty proceeding when operated with only solid catalysts. We report here the organic-electrolyte-dissolved iron phthalocyanine (FePc) as a shuttle of (O2)(-) species and electrons between the surface of the electronic conductor and the insulator Li2O2 product of discharge. The Li2O2 is observed to grow and decompose without direct contact with carbon, which greatly enhances the electrochemical performance. Our results signal that the use of molecular shuttles that are catalytically active may prove to be enablers of a practical lithium-air rechargeable battery.

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White organic light‐emitting diodes (WOLEDs) are highly attractive in the fields of solid‐state lighting. The biggest challenge that is facing at present is how to maximize the exciton utilization to further enhance the efficiency, while taking into account the stability. Here, highly efficient all‐fluorescence and fluorescence/phosphorescence (F/P) hybrid WOLEDs with low efficiency roll‐off by designing exciplex‐sandwich emissive architecture and precisely manipulating the exciton allocation are demonstrated. The resulting complementary‐color hybrid WOLEDs realize the maximum external quantum efficiency of 28.3% and power efficiency of 102.9 lm W−1, and remain 26.9% and 73.5 lm W−1 at 500 cd m−2 and yet as high as 25.8% and 63.5 lm W−1 at 1000 cd m−2, respectively, revealing very low roll‐off. By using the efficient blue exciplex combined with red and green phosphorescent emitters, the three‐color WOLEDs yield a high color rendering index of 86, an external quantum efficiency of 29.4%, and a power efficiency of 75.5 lm W−1. It is anticipated that the exciplex engineering will open an efficient avenue to precisely allocate excitons, and finally producing high‐performance WOLEDs for next‐generation solid‐state lighting technology.

wileyonlinelibrary.compast few years, hybrid WOLEDs, combining the blue fl uorophors and longwavelength phosphors, have attracted substantial attention owing to the unique merits of high effi ciency and excellent stability. [ 2 ] In principle, to achieve a theoretical maximum internal quantum efficiency for hybrid WOLEDs, a prerequisite key is that all electrically generated singlet and triplet excitons must be effectively utilized for the white emission. [ 2,3 ] Enormous efforts have been devoted to simultaneously harvest both the singlet and triplet excitons in single-emissive-layer (single-EML), [ 4 ] and multi-emissive-layer (multi-EML) hybrid WOLEDs. [ 5 ] In the single-EML hybrid WOLEDs, the precise manipulation of phosphorescent emitter concentration in blue fl uorophore host is very necessary to suppress the singlet exciton transfer from the blue fl uorophore to the phosphors via Förster energy transfer. In this case, the phosphorescent dopant concentration and the property of used blue fl uorophore host have obvious effects on the device performance and there exist the problems of notorious spectrum shift with the increased operational voltages. Alternatively, the multi-EML counterparts provide a reliable strategy Thermally activated delayed fl uorescence (TADF)-based white organic lightemitting diodes (WOLEDs) are highly attractive because the TADF emitters provide a promising alternative route to harvest triplet excitons. One of the major challenges is to achieve superior effi ciency/color rendering index/ color stability and low effi ciency roll-off simultaneously. In this paper, highperformance hybrid WOLEDs are demonstrated by employing an effi cient blue TADF emitter combined with red and green phosphorescent emitters. The resulting WOLED shows the maximum external quantum effi ciency, current effi ciency, and power effi ciency of 23.0%, 51.0 cd A −1 , and 51.7 lm W −1 , respectively. Moreover, the device exhibits extremely stable electroluminescence spectra with a high color rendering index of 89 and Commission Internationale de L'Eclairage coordinates of (0.438, 0.438) at the practical brightness of 1000 cd m −2 . The achievement of these excellent performances is systematically investigated by versatile experimental and theoretical evidences, from which it is concluded that the utilization of a blue-green-red cascade energy transfer structure and the precise manipulation of charges and excitons are the key points. It can be anticipated that this work might be a starting point for further research towards high-performance hybrid WOLEDs.

The photophysical properties of four new quinoxaline derivatives featuring both AIE and TADF characteristics were controlled to give high EQEs.