A light-emitting diode (LED) is a semiconductor that emits light when an electric current flows through it. The first practical application of LEDs was in the remote control circuits as an infrared (IR) source. Modern LEDs are available in all visible, ultraviolet, and infrared spectrums. Pretty much every electronic device that we use today contains LEDs – lights, displays, indicator lights in electronics, to name a few.
High quality LED that is both energy efficient and bright requires a higher temperature and an elaborate deposition technique to fabricate them, which entails high production costs.
Recent joint research led by Chair Professor from the Department of Materials Science and Engineering at CityU and Professor Yang Xuyong from Shanghai University focuses on perovskite. Perovskites are a class of compounds with the same crystal structure as calcium titanium oxide (CaTiO3). The researchers have developed a LED using a 2-D perovskite material that is highly energy-efficient and offers bright colors. More importantly, the LEDs can be fabricated at room temperature, reducing the overall production costs.
The researchers published their findings in the scientific journal Nature Communications.
In this study, the team used a 2-D perovskite that is about a nanometre thick. An addition of around 10% of methanesulfonate (MeS), a simple organic compound, reconstructs the structure and enhances the exciton energy transfer between sheets of different thicknesses, greatly enhancing the electro-luminescence. The MeS also reduces the number of defects in the 2-D perovskite material.
The LEDs produced a brightness of 13,400 candela/m2 at 5.5 V and an external quantum efficiency of 20.5%, which is close to the maximums that many existing LED technologies can achieve.
According to Professor Rogach, “The high brightness, excellent color purity, and commercial-grade operating efficiency that has been achieved marks 2-D perovskites as an extremely attractive material for future commercial LEDs, and potentially also display technology. It’s a tangible outcome from both fundamental and applied research into novel nano-scale materials.”
This research has taken perovskite LEDs on par with today’s commercial display technologies like organic LEDs.
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