Improving efficiency, brightness of perovskite LEDs

Advances in organic phosphorescent materials are opening new opportunities for organic light-emitting diodes for combined electronics and light applications, including solar cells, photodiodes, optical fibers and lasers.

Tuning the energy levels of organic semiconductors

Physicists from the Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and the Center for Advancing Electronics Dresden (cfaed) at the TU Dresden, together with researchers from Tübingen, Potsdam ...

LED device could increase memory retention among astronauts

Hanli Liu, a professor of bioengineering at The University of Texas at Arlington, is working to improve memory and cognitive function in astronauts during space missions by directing light onto their brains.

Substrate defects key to growth of 2-D materials

Creating two-dimentional materials large enough to use in electronics is a challenge despite huge effort but now, Penn State researchers have discovered a method for improving the quality of one class of 2-D materials, with ...

Smart pill bottle keeps drugs safe

Low-cost, stretchy sensors can be assembled inside the lid of a drug container to help monitor patient safety.

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Light-emitting diode

A light-emitting diode (LED) (pronounced /ˌɛliːˈdiː/, or just /lɛd/), is an electronic light source. The LED was first invented in Russia in the 1920s, and introduced in America as a practical electronic component in 1962. Oleg Vladimirovich Losev was a radio technician who noticed that diodes used in radio receivers emitted light when current was passed through them. In 1927, he published details in a Russian journal of the first ever LED.

All early devices emitted low-intensity red light, but modern LEDs are available across the visible, ultraviolet and infra red wavelengths, with very high brightness.

LEDs are based on the semiconductor diode. When the diode is forward biased (switched on), electrons are able to recombine with holes and energy is released in the form of light. This effect is called electroluminescence and the color of the light is determined by the energy gap of the semiconductor. The LED is usually small in area (less than 1 mm2) with integrated optical components to shape its radiation pattern and assist in reflection.

LEDs present many advantages over traditional light sources including lower energy consumption, longer lifetime, improved robustness, smaller size and faster switching. However, they are relatively expensive and require more precise current and heat management than traditional light sources.

Applications of LEDs are diverse. They are used as low-energy indicators but also for replacements for traditional light sources in general lighting and automotive lighting. The compact size of LEDs has allowed new text and video displays and sensors to be developed, while their high switching rates are useful in communications technology.

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