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The efficiency and operational lifetime of quantum dot (QD) based light-emitting diodes (QLEDs) are essentially affected by the electron–hole charge balance. Although various methods have been reported to improve the charge balance, these methods cause issues at the same time, such as increasing a driving voltage and complicating a device structure. In this work, we introduce hybrid InP/ZnSeS/ZnS QDs, in which the oleic acid ligands are substituted with semiconducting diblock copolymer units possessing hole-transporting carbazole groups, to facilitate hole injection and to reduce electron leakage. As a result, the efficiency and the operational lifetime were improved by 1.4-fold and 4-fold, respectively, with lower driving voltages. Origins of the results were systematically investigated, and we found that the diblock copolymer units surrounding the QDs made the inter-dot distance farther apart from one another, leading to reduced Forster resonance energy transfer between QDs which can cause reduced photoluminescence quantum yields. Also, the hole transporting ability of carbazole groups facilitated hole injection into QDs and blocked excess electron leakage at the same time. The impedance spectroscopy on the devices with the pristine and hybrid QDs before and after bias stress revealed that hole accumulation at the hole transport layer/QD interface significantly affected the operational lifetime of the QLEDs. This work offers a design for the QD emission layer to achieve efficient and stable QLEDs with systematic understanding of the origins.

We report the photocatalytic conversion of CO2 to CH4 using CuPt alloy nanoclusters anchored on TiO2. As the size of CuPt alloy nanoclusters decreases, the photocatalytic activity improves significantly. Small CuPt nanoclusters strongly bind CO2 intermediates and have a stronger interaction with the TiO2 support, which also contributes to an increased CH4 generation rate. The alloying and size effects prove to be the key to efficient CO2 reduction, highlighting a strategic platform for the design of photocatalysts for CO2 conversion.

We demonstrate QLEDs implementing wider active layers (50 nm) based on QD–conducting polymer nanohybrids, which exhibit a stable operational device performance across a wide range of current densities and brightness. A comparative study reveals that the significant suppression of efficiency roll-off in the high current density regime is primarily attributed to a sufficient charge carrier distribution over the wider active layer and improved charge carrier balance within QDs enabled by the hybridization of QDs with conducting polymers. Utilization of this finding in future studies should greatly facilitate the development of high performance, stable QLEDs at high current density or luminance regime toward displays or solid-state lighting applications.

Robust, processable, and bright quantum dot/organosilicate (QD/OS) hybrid films with uniform QD distribution are successfully demonstrated by grafting thiol-containing polymeric organosilicate (OS) ligands to the surface of QDs. It is found that the surface modified QDs show almost the same optical properties (i.e., in terms of emission PL spectra and quantum yields (QYs)) as those of pristine QDs initially covered with oleic acids. The QD/OS hybrid films based on the surface modified QDs show the uniform distribution of QDs within the films with all the beneficial properties such as high QY, improved environmental resistance against hydrochloric acid, and excellent optical transparency in the visible range. In addition, red, green, blue, and white QD/OS hybrid films with high color purity and a down-conversion film, based on a mixture of red and green QDs, placed on top of a blue LED chip showing white emission were also successfully demonstrated with the QD/OS hybrids. We further demonstrate that cylinder-patterned QD/OS hybrid films are possible simply by applying unconventional imprint lithography. The QD/OS hybrid films with uniform distribution of QDs within the films could thus be applied as practical platforms, which have easy processability, high QY, and environmental stability, for optical devices based on functional nanocrystals.

Semiconducting hole transporting block copolymers were chemically modified to adjust their energy levels to that of CdSe/CdS/CdZnS red quantum dots. Hybrids with optimized energy levels could be used to build strongly improved quantum dot based LEDs (QLEDs).