New technology of colloidal quantum dots improves the disadvantages of high energy consumption and high cost of traditional LED displays

LED lights have become a ubiquitous lighting solution for homes and businesses, but traditional LED have documented their shortcomings when it comes to large, high-resolution displays. LED displays use high voltages and a factor called internal power conversion efficiency is low, which means that the energy cost of running the display is high, the display life is not long, and it can run too hot.

In a paper published in Nano Research, the researchers outline how a technological advance called quantum dots could address some of these challenges. Quantum dots are tiny artificial crystals that act as semiconductors. Due to their size, they have unique properties that can make them useful in display technology.


Xing Lin, an assistant professor of information science and electronic engineering at Zhejiang University, said traditional LED have been successful in fields such as display, lighting and optical communications. However, the techniques used to obtain high-quality semiconductor materials and devices are very energy-intensive and cost-intensive. Colloidal quantum dots offer a cost-effective way to build high-performance LED using inexpensive solution processing techniques and chemical-grade materials. Furthermore, as inorganic materials, colloidal quantum dots surpass emissive organic semiconductors in terms of long-term operational stability.

All LED displays are composed of multiple layers. One of the most important layers is the emissive layer, where electrical energy is turned into colorful light. The researchers used a single layer of quantum dots as the emission layer. Typically, the colloidal quantum dot emission layer is the source of voltage loss because of the poor conductivity of colloidal quantum dot solids. By using a single layer of quantum dots as the emissive layer, the researchers speculate that they could reduce the voltage to the maximum to power these displays.


Another feature of quantum dots that makes them ideal for LED is that they can be manufactured without any defects that would affect their efficiency. Quantum dots can be designed without impurities and surface defects. According to Lin, quantum dot LED (QLED) can achieve near-unity internal power conversion efficiencies at current densities suitable for display and lighting applications. Conventional LED based on epitaxially grown semiconductors exhibit severe efficiency roll-off within the same current density range. This difference stems from the defect-free nature of high-quality quantum dots.


The relatively low cost of producing emissive layers with quantum dots and the ability to use optical engineering techniques to improve the light extraction efficiency of QLED, the researchers suspect, could effectively improve traditional LED used in lighting, displays, and more. But there is still more research to be done, and current QLED have some shortcomings that need to be overcome before they can be widely adopted.


According to Lin, the research has shown that thermal energy can be extracted to improve the efficiency of electro-optical power conversion. However, device performance at this stage is far from ideal in the sense of relatively high operating voltages and low current densities. These weaknesses can be overcome by seeking better charge transport materials and designing the interface between charge transport and quantum dot layers. The ultimate goal—to realize electroluminescent cooling devices—should be QLED-based.


Post time: Sep-18-2023

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