Carbon quantum dots (CQDs) have emerged as promising materials for optoelectronic applications on account of carbon’s intrinsic merits of high stability, low cost, and environment-friendliness. However, the CQDs usually give broad emission with full width at half maximum exceeding 80 nm, which fundamentally limit their display applications. Here we demonstrate multicolored narrow bandwidth emission (full width at half maximum of 30 nm) from triangular CQDs with a quantum yield up to 54–72%. Detailed structural and optical characterizations together with theoretical calculations reveal that the molecular purity and crystalline perfection of the triangular CQDs are key to the high color-purity. Moreover, multicolored light-emitting diodes based on these CQDs display good stability, high color-purity, and high-performance with maximum luminance of 1882–4762 cd m−2 and current efficiency of 1.22–5.11 cd A−1. This work will set the stage for developing next-generation high-performance CQDs-based light-emitting diodes.

Near-infrared-emissive polymer-carbon nanodots (PCNDs) are fabricated by a newly developed facile, high-output strategy. The PCNDs emit at a wavelength of 710 nm with a quantum yield of 26.28%, which is promising for deep biological imaging and luminescent devices. Moreover, the PCNDs possess two-photon fluorescence; in vivo bioimaging and red-light-emitting diodes based on these PCNDs are demonstrated.

As an emerging building unit, carbon dots (CDs) have been igniting the revolutionaries in the fields of optoelectronics, biomedicine, and bioimaging. However, the difficulty of synthesizing CDs in aqueous solution with full‐spectrum emission severely hinders further investigation of their emission mechanism and their extensive applications in white light emitting diodes (LEDs). Here, the full‐color‐emission CDs with a unique structure consisting of sp3‐hybridized carbon cores with small domains of partially sp2‐hybridized carbon atoms are reported. First‐principle calculations are initially used to predict that the transformation from sp3 to sp2 hybridization redshifts the emission of CDs. Guided by the theoretical predictions, a simple, convenient, and controllable route to hydrothermally prepare CDs in a single reaction system is developed. The prepared CDs have full‐spectrum emission with an unprecedented two‐photon emission across the whole visible color range. These full‐color‐emission CDs can be further nurtured by slight modifications of the reaction conditions (e.g., temperature, pH) to generate the emission color from blue to red. Finally a flexible LEDs with full‐color emission by using epoxy CDs films is developed, indicating that the strategy affords an industry translational potential over traditional fluorophores.

Piezochromic materials, which show color changes resulting from mechanical grinding or external pressure, can be used as mechanosensors, indicators of mechano-history, security papers, optoelectronic devices, and data storage systems. A class of piezochromic materials with unprecedented two-photon absorptive and yellow emissive carbon dots (CDs) was developed for the first time. Applied pressure from 0-22.84 GPa caused a noticeable color change in the luminescence of yellow emissive CDs, shifting from yellow (557 nm) to blue-green (491 nm). Moreover, first-principles calculations support transformation of the sp domains into sp -hybridized domains under high pressure. The structured CDs generated were captured by quenching the high-pressure phase to ambient conditions, thus greatly increasing the choice of materials available for a variety of applications.

Light-emitting chiral carbonized polymer dots (Ch-CPDs) are attracting great interest because of their extraordinary photonic properties,b ut modulating their band-gap emission, especially at long wavelength, and maintaining their chiral structure to achieve multicolor,high-emission Ch-CPDs remains challenging.R eported here for the first time is the synthesis of red-and multicolor-emitting Ch-CPDs using the common precursors l-/d-tryptophan and o-phenylenediamine, and asolvothermal approach at one temperature.The quantum yield of the Ch-CPDs was between 31 %a nd 54 %. Supramolecular self-assembly provided multicolor-emitting Ch-CPDs showing novel circularly polarized luminescence,w ith the highest dissymmetric factor (g lum )o f1 10 À2 .I mportantly, circularly polarized white-emitting CPDs were fabricated for the first time by tuning the mixing ratio of the three colored Ch-CPDs in agel. This strategy affords exciting opportunities for designing functional chiroptical materials.

Lead halide perovskites have attracted tremendous attention because of their impressive optoelectronic properties. However, the toxicity of lead remains a bottleneck for further commercial development. Two-dimensional Ruddlesden−Popper tin-based perovskites are lead-free and more stable compared to their three-dimensional counterparts, which have great potential in the optoelectronic device field. Herein, we demonstrate high-quality two-dimensional phenylethylammonium tin-iodide perovskite (PEA 2 SnI 4 ) thin films by using toluene as the antisolvent. Furthermore, the PeLED performance is greatly improved by replacing the PEAI spacer cation with 2thiopheneethyllamine iodide (TEAI). As a result, a TEA-based PeLED device is achieved with a low turn-on voltage of 2.3 V, a maximum luminance of 322 cd m −2 , and maximum external quantum efficiency of 0.62%, which are the highest efficiency and brightness for pure red (emission peak = 638 nm) tin-based PeLEDs to date.

A recently created class of inorganic 2D materials, MXenes, has become a subject of intensive research. Reducing their dimensionality from 2D to 0D quantum dots (QDs) could result in extremely useful properties and functions. However, this type of research is scarce, and the reported Ti 3 C 2 MXene QDs (MQDs) have only shown blue fluorescence emission. This work demonstrates a facile, high‐output method for preparing bright white emitting Ti 3 C 2 MQDs. The resulting product is two layers thick with a lateral dimension of 13.1 nm. Importantly, the as prepared Ti 3 C 2 MQDs present strong two‐photon white fluorescence. Their fluorescence under high pressure is also investigated and it is found that the white emission is very stable and the pressure makes it possible to change from cool white emission to warm white emission. Hybrid nanocomposites are then fabricated by polymerizing Ti 3 C 2 MQDs in polydimethylsiloxane (PDMS) solution, and the bright white emitting hybrid materials in white light‐emitting diodes are used. This work provides a facile and general approach to modulate various nanoscale MXene materials, and could further aid the wide development of applications for MXene materials in various optical‐related fields.

Lead-free halide double perovskites have been proposed as candidates to replace Pb-halide perovskites in photovoltaic and optoelectronic applications due to their enhanced stability and nontoxicity. However, the limited understanding of the fundamental properties of halide double perovskites represents a hurdle to further improvement of their device performance. Our experimental studies demonstrate that the broad emission of Cs2AgBiCl6 with a large Stokes shift stems primarily from exciton self-trapping owing to strong electron–phonon coupling. An unusual blue shift of the emission accompanied by a red shift of the absorption edge occurred due to the reduced lattice relaxation energy upon lattice compression in the cubic phase. Electron–phonon coupling reduction is critical to the enhancement of photoluminescence intensity and tuning emission range in Cs2AgBiCl6 under high pressure. The structure–property relationships illuminated by our work can provide the basis for improving the performance of halide double perovskites.