Scientists discover warm light-emitting by utilising quantum dots

A research team from Chongqing University, China, have discovered warm white light-emitting with high, efficient emission and high colour rendering index by using ligand modified CsPbBr3 quantum dots.

How does this help the world’s energy consumption?

Lighting currently accounts for roughly one-fifth of the global electricity consumption, which leads to a large increase in the emissions of Carbon Dioxide (CO2). In order to reduce the current energy demand for lighting, solid-state white light-emitting diodes (WLEDs) are becoming the most capable illumination sources.

Additionally, the WLEDs are a much more efficient source of power; the energy savings and environmental friendliness is much higher than that of traditional bulbs or fluorescent lighting sources.

What are the typical drawbacks of WLEDs?

White light emission is typically achieved through the composition of near-UV or blue LEDs with a coating of either down-conversion materials, such as YAG: Ce3+ phosphors, or a combination of red and green phosphors.

Unfortunately, WLEDs constructed through this method suffer from poor white light performance after extensive utilisation, due to the different degradation rates between the blue LEDs and phosphors.

In addition to this, WLEDs generally exhibit unsatisfactory high correlated colour temperature (CCT) value and a low colour rendering index (CRI <80) due to the facile absence of the red or green emission.

Therefore, an optimum white light emitting system needs the light source with an appropriate CCT between 2500 and 6500 K, and CRI above 80. Among the luminescent materials discovered so far, CsPbBr3 perovskite quantum dots (QDs) have been recognised as one of the most promising candidates for WLEDs due to the excellent optoelectronic properties.

How did scientists use quantum dots to create sufficient WLEDs?

Professor Zhigang Zang, leader of the study from Chongqing University, presents a facile strategy to achieve excellent stability of CsPbBr3 quantum dots, and high performance of WLEDs by using shorter 2-hexyldecanoic acid (DA) ligand to replace OA ligand for CsPbBr3 quantum dots.

The ligand modified CsPbBr3 quantum dots exhibit a high PLQY of 96% with significantly enhanced stability, even when exposed to ethanol and water environments. Consequently, modified CsPbBr3 quantum dots and red AgInZnS quantum dots are created by employing WLEDs and combining a blue InGaN LED with green ligand, which generates high quality warm white light emission.

Scientists concluded that WLEDs created from the modified CsPbBr3 quantum dots portray a good thermal performance under high driving current, therefore verifying their potential application in the field of solid-state lighting.

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