The seeded growth method offers an efficient way to design core–shell semiconductor nanocrystals in the liquid phase. The combination of seed and shell materials offers wide tunability of morphologies and photophysical properties. Also, semiconductor nanorods (NRs) exhibit unique polarized luminescence which can potentially break the theoretical limit of external quantum efficiency in light emitting diodes based on spherical quantum dots. Although rod‐in‐rod core–shell NRs present higher degree of polarization, most studies have focused on dot‐in‐rod core–shell NRs due to the difficulties in achieving uniform NR seeds. Here, this study prepares high‐quality uniform CdSe NRs by improving the reactivity of the Se source, using a secondary phosphine, namely diphenylphosphine, to dissolve the Se power, along with the conventional tertiary phosphine, namely trioctylphosphine. Starting from these high‐quality NR seeds, this study synthesizes CdSe/CdxZn1−xS/ZnS core–shell NRs with narrow emission bandwidth (29 nm at 620 nm), high PLQY (89%) and high linear polarization (p = 0.90). This study then assembles these core–shell NRs using the confined assembly method and fabricates long‐range‐ordered microarrays with programmable patterns and displaying highly polarized emission (p = 0.80). This study highlights the great potential of NRs for application in liquid crystal displays and full‐color light emitting diodes displays.
Radiation detectors are widely used in physics, material science, chemistry, and biology. Halide perovskites are known for their superior properties including tunable bandgaps and chemical compositions, high defect tolerance, solution-processable...
Formamidinium lead bromide (FAPbBr3) nanocrystals
(NCs)
have been demonstrated to exhibit ideal ultrapure green luminescence
at 530 nm and to hold great potential in light-emitting diodes, by
potentially overcoming the difficulties facing cesium lead bromide
(CsPbBr3) NCs. However, compared to all-inorganic lead
halide perovskite NCs, organic–inorganic hybrid FAPbBr3 NCs are sensitive to moisture, oxygen, and heat due to their
intrinsic instability caused by the organic cations (FA+). Herein, we present an epitaxial growth method for the overgrowth
of a large-band-gap cesium lead halide (Cs4PbBr6) shell on the surface of FAPbBr3 NCs. The resulting core/shell
NCs show a near-unity photoluminescence quantum yield (PLQY) of 97.1%,
the emission with full width at half-maxima of 88 meV, and long-term
environmental stability. The introduction of Cs+ into FAPbBr3 NCs can inhibit the migration of FA+ and suppress
the phase transformation from cubic phase to tetragonal phase at 60
°C. Furthermore, the existence of shell can provide stronger
exciton confinement and improve the thermal stability of FAPbBr3 NCs. The core/shell perovskite NCs developed in this study
have the advantages of high PLQY and good stability and may contribute
to the field of light-emitting diodes (LEDs).
Quantum dot (QD) based light-emitting diodes (QLEDs) hold great promise for next-generation lighting and displays. In order to reach a wide color gamut, deep red QLEDs emitting at wavelengths beyond 630 nm are highly desirable but have rarely been reported. Here, we synthesized deep red emitting ZnCdSe/ZnSeS QDs (diameter ∼16 nm) with a continuous gradient bialloyed core− shell structure. These QDs exhibit high quantum yield, excellent stability, and a reduced hole injection barrier. The QLEDs based on ZnCdSe/ZnSeS QDs have an external quantum efficiency above 20% in the luminance range of 200−90000 cd m −2 and a record T 95 operation lifetime (time for the luminance to decrease to 95% of its initial value) of more than 20000 h at a luminance of 1000 cd m −2 . Furthermore, the ZnCdSe/ZnSeS QLEDs have outstanding shelf stability (>100 days) and cycle stability (>10 cycles). The reported QLEDs with excellent stability and durability can accelerate the pace of QLED applications.
Lead-free copper halide perovskite nanocrystals (NCs) are emerging materials with excellent photoelectric properties. Herein, we present a colloidal synthesis route of orthorhombic Cs2CuCl4 NCs with well-defined cubic shape and an average diameter of 24 ± 2.1 nm. The Cs2CuCl4 NCs exhibit bright deep blue photoluminescence, which is attributed to the Cu(II) defects. In addition, passivating the Cs2CuCl4 NCs by Ag+ can effectively improve the photoluminescence quantum yield (PLQY) and environmental stability.
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