Displays - Page 8

Researchers at ETH Zurich have used perovskite materials to create ultra-pure green light for new light-emitting diodes that may pave the way for visibly improved color quality in TVs and smartphones. "To date, no one has succeeded in producing green light as pure as we have," says the ETH Zurich team.

The team explains that it is basically already possible to achieve efficient-enough red and blue light, while green light still needs to improve. This is, the team says, due mainly to human perception, since the eye is able to distinguish between more intermediary green hues than red or blue ones. "This makes the technical production of ultra-pure green very complex, which creates challenges for us when it comes to developing technology and materials," says co-lead author of the report.

Researchers from Ludwig-Maximilians-Universitaet (LMU) in Munich and the Johannes Kepler University (JKU) in Austria have designed a method to tune the color of the light emitted by a LED by altering the size of its semiconductor crystals.

The method enables the production of semi-conducting nanocrystals of defined size based on perovskites. The crystals are extremely stable, which ensures that the LEDs exhibit high color fidelity ' an important criterion of quality. Moreover, the resulting semiconductors can be printed on various surfaces, and are thus promising for the manufacture of LEDs for use in displays.

Researchers at Pohang University in Korea are reportedly the first to develop a perovskite light emitting diode (PeLED) that could replace organic LED (OLED) and quantum dot LED (QDLED).

Organic/inorganic hybrid perovskite have much higher color-purity at a lower cost compared to organic emitters and inorganic QD emitters. However, LEDs based on perovskite had previously shown a limited luminous efficiency, mainly due to significant exciton (a complex of an electron and hole that can allow light emission when it is radiatively recombined) dissociation in perovskite layers.

Scientists at Nanjing University of Science and Technology, China, and colleagues have used quantum dots based on perovskites for QD-based light-emitting devices (QLEDs). These (completely inorganic) materials reportedly solve the stability problem of previously developed hybrid organic'inorganic halide perovskites.

Quantum dots (QDs) are nanometer-sized semiconductor materials with highly tunable properties such as bandgap, emission color, and absorption spectrum. These characteristics depend on their size and shape, which can be controlled during the synthesis. The quantum dots' luminescence wavelength can be tuned by both their size and by the halide ratio. In this research, the team made blue, green, and yellow QLEDs with high quantum yields, using the perovskite quantum dots as the emitting layer. The researchers state that this development could allow the design of new optoelectronic devices, such as displays, photodetectors, solar cells, and lasers.