Close to 100%! Perovskite based LED has a luminous efficiency record.

09 November 2018, 08:16 source: Science and Technology Daily
 
Original title: close to 100%! Perovskite based LED has a luminous efficiency record.

Scientists integrate calcium titanium deposits into LED.

Source: Official Website of University of Cambridge, UK

According to the official website of University of Cambridge, the scientists in the University have incorporated the calcium titanium deposit into the light-emitting diode (LED). The internal luminous efficiency of the product is close to a record 100%, which is comparable to the best organic LED (OLED). It is expected to be applied to display, lighting, communications and the next generation of solar cells in the future.

Compared with OLED, which is widely used in high-end consumer electronics products, perovskite based LED has lower manufacturing cost and can emit light with high color purity. Although scientists have previously developed perovskite LED, the products obtained will convert electricity to light less efficiently than conventional OLED. The mixed perovskite based LED, developed by Professor Richard Fred of University of Cambridge, Cavendish laboratory, has limited their luminous efficiency due to the loss of calcium and titanium deposits caused by tiny defects in their internal crystal structure.

Now, the team has proved by new research that perovskite and polymer can form a composite layer to achieve higher luminous efficiency, which is close to the theoretical efficiency limit of OLED film. The findings are published in the latest issue of nature photonics.

The perovskite polymer composite layer in the LED device is made of two dimensional, three dimensional perovskite and insulating polymer. When the ultra fast laser is irradiated on the structure, the energy carrying charge moves from the two-dimensional region to the three-dimensional region within 1/1000000000000 seconds. Then, the "self governed" charge in the three dimensional region is effectively reassembled and illuminated.

Dr David Dave, one of the authors of the paper, explained: "energy transfer from 2D to 3D occurs very fast, and the charge in the three dimensional region is isolated from the defects of polymer. These mechanisms can prevent defects from" disrupting "and thus prevent energy loss. This is the first time scientists have realized this on perovskite based products.

Although perovskite LED has begun to compete with OLED in terms of efficiency, its stability is poor at present and can not be used in consumer electronics for the time being. When the perovskite LED was first introduced, its life expectancy lasted only a few seconds. The half-life of perovskite based LED in the new research is about 50 hours. Although it has improved a lot, it is far from the commercial life requirement. To achieve this, a broad industrial development plan is needed. "Understanding the degradation mechanism of LED is the key to future improvements," Di Dawei said. (reporter Liu Xia)

(Editor: Wang Shaoshao, He Yingchun)

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