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This work examines how the optimization of molecular dimensions and chemical functionality of the organic ligands of quantum dots (QDs) can be explored for dramatic enhancement of the optical properties of QD films, particularly, optical gain. We show that the replacement of traditional QD organic ligands with a much shorter ligand, butylamine, yields a dense QD-packing that results in a two-fold increase in optical gain. Overall, the highly packed QD films exhibit very large net gain values (∼500 cm−1) which greatly exceed typical Cd-based QD films with traditional ligands. In addition, thresholds for amplified-spontaneous emission (ASE) down to 50 μJ cm−2 were observed, which is exceptionally low for ns-pulse pumped QD systems. Our results confirm an additional route for obtaining high optical gain using QDs, and outline a strategy for modifying the optical gain characteristics by ligand exchange without needing to modify the QD selection. Consideration of the ligands along with QD compositional design could make it possible to fabricate photonic systems with exceptionally low lasing thresholds, and offers a route toward achieving high gain using steady state pumping, an extremely difficult feat to achieve in traditional QD systems. [ABSTRACT FROM AUTHOR]

We demonstrate herein the design and fabrication of a highly efficient yellow organic light-emitting diode (OLED) with a balanced carrier injection device architecture having a zero electron-injection-barrier host blended with a hole-injection aiding co-host. The resultant yellow OLED showed, at 1000 cd m−2 for example, an efficacy of 59 lm W−1, current efficiency of 71 cd A−1 and external quantum efficiency (EQE) of 23%, with values of 42 lm W−1, 47 cd A−1 and 15% EQE without a co-host. The co-host effect that resulted in very balanced carrier injection was also valid for other yellow OLED devices and their efficiency improvement was also very marked. With the use of a micro-lens, the device efficiency is further improved to 79 lm W−1, 96 cd A−1 and 30% EQE. [ABSTRACT FROM AUTHOR]

Low color temperature (CT) lighting sources are crucial for their low suppression of melatonin secretion, and high power efficiency is essential for energy-saving. This study demonstrates the incorporation of a blend interlayer between emissive layers to improve the device performance of low CT organic light emitting diodes. The resulting devices exhibit a CT much lower than that of incandescent bulbs, which is ∼2500 K with a ∼15 lm W−1efficiency, and even as low as that of candles, which is ∼2000 K with ∼0.1 lm W−1. The best device fabricated shows an external quantum efficiency of 22.7% and 36 lm W−1(54 cd A−1) with 1880 K at 100 cd m−2, or 20.8% and 29 lm W−1(50 cd A−1) with 1940 K at 1000 cd m−2. The high efficiency of the proposed device may be attributed to its interlayer, which helps effectively distribute the entering carriers into the available recombination zones. [ABSTRACT FROM AUTHOR]

Nitroxide polymer brushes were covalently patterned on flexible conducting substrates viasurface-initiated atom transfer radical polymerization and microcontact printing. As a cathode of organic radical batteries, the nitroxide polymer brushes prevent the nitroxide polymer from dissolving into electrolyte solvents, which improves the cycle-life performance of batteries. [ABSTRACT FROM AUTHOR]