A novel BODIPY‐containing organic small molecule is synthesized and employed as a down‐converting layer on a commercial blue light‐emitting diode (LED). The resulting hybrid device demonstrates white‐light emission under low‐current operation, with color coordinates of (0.34, 0.31) and an efficacy of 13.6 lm/W; four times greater than the parent blue LED.

InGaN/GaN multiple quantum wells (MQWs) have been studied by using cathodoluminescence hyperspectral imaging with high spatial resolution. Variations in peak emission energies and intensities across trenchlike features and V-pits on the surface of the MQWs are investigated. The MQW emission from the region inside trenchlike features is redshifted by approximately 45 meV and more intense than the surrounding planar regions of the sample, whereas emission from the V-pits is blueshifted by about 20 meV and relatively weaker. By employing this technique to the studied nanostructures it is possible to investigate energy and intensity shifts on a 10 nm length scale.

Hyperspectral cathodoluminescence imaging provides spectrally and spatially resolved information on luminescent materials within a single dataset. Pushing the technique toward its ultimate nanoscale spatial limit, while at the same time spectrally dispersing the collected light before detection, increases the challenge of generating low-noise images. This article describes aspects of the instrumentation, and in particular data treatment methods, which address this problem. The methods are demonstrated by applying them to the analysis of nanoscale defect features and fabricated nanostructures in III-nitride-based materials.

We combine two scanning electron microscopy techniques to investigate the influence of dislocations on the light emission from nitride semiconductors. Combining electron channeling contrast imaging and cathodoluminescence imaging enables both the structural and luminescence properties of a sample to be investigated without structural damage to the sample. The electron channeling contrast image is very sensitive to distortions of the crystal lattice, resulting in individual threading dislocations appearing as spots with black–white contrast. Dislocations giving rise to nonradiative recombination are observed as black spots in the cathodoluminescence image. Comparison of the images from exactly the same micron-scale region of a sample demonstrates a one-to-one correlation between the presence of single threading dislocations and resolved dark spots in the cathodoluminescence image. In addition, we have also obtained an atomic force microscopy image from the same region of the sample, which confirms that both pure edge dislocations and those with a screw component (i.e., screw and mixed dislocations) act as nonradiative recombination centers for the Si-doped c-plane GaN thin film investigated.

The synthesis and characterisation of two novel organic down-converting molecules is disclosed, together with their performance as functional colour-converters in combination with inorganic blue light-emitting diodes (LEDs). Each molecule contains two fluorene-triphenylamine arms, connected to either a benzothiadiazole or bisbenzothiadiazole core. These molecules have been selected on the basis that they are free from absorption bands in the green region of the visible spectrum to maximise their performance and offer improvements compared with previous BODIPY-containing analogues. The inorganic InGaN/GaN LED emits at 444 nm, overlying the absorption of each of the organic molecules. The combination of the blue (inorganic) and yellow (organic) emission is shown to produce reasonable quality, white light-emitting hybrid devices for both down-converter molecules. Cool to warm white light is achieved for both molecules by increasing the concentration. An optimum colour rendering index (CRI) value of 66 is obtained for the mono-benzothiadiazole molecule. Also a high blue-to-white efficacy (defined as white luminous flux (lm)/blue radiant flux (W)) of 368 lm W⁻¹ is achieved, superseding the current phosphor converters of 200–300 lm W⁻¹. A comparison of these down-converting molecules to the older generation BODIPY-containing molecules is also provided.

One of the most important non-radiative relaxation processes that limits the quantum yield of a fluorophore is related to aggregation of the molecules in the solid-state causing excimer quenching. To limit this quenching mechanism, the fluorophore can be contained within a well-ordered 3D system that minimises aggregation through rigid bonds and spatial separation in a defined topological construct. Herein, the synthesis, characterisation and application as a down-converter of a new luminescent 3D material (MOF-BTBMBA) that incorporates a building block based on a benzothiadiazole (BT) derivative (BTBMBA) in a metal–organic framework (MOF) is presented. Notably, the photoluminescence quantum yield and hybrid LED performance are significantly improved for the MOF-based device compared to that prepared with the free ligand, highlighting the effectiveness of the rigid scaffold arrangement.