Blue light means a big improvement for perovskite-based LEDs

Researchers at Linköping University, Sweden, have developed effective blue light emission codes based on halide perovskites. “We are delighted with this progress,” said Feng Gao, a professor at Linköping University, whose new LEDs may open the way to cheap and energy-efficient lighting.

Lighting accounts for around 20% of global electricity consumption, a figure that could be reduced to 5% if all light sources had light emitting codes (LEDs). The blue-and-white LEDs currently in use, however, require complex and expensive manufacturing methods, which makes it more difficult to achieve global transition.

LEDs made with halide perovskites could be a cheaper and friendlier option for both lighting and LED-based monitors. Perovskites as a family of semiconducting materials are defined by their cubic crystal structure. They have good lighting properties and are easy to make. Using elements from the halogen group, ie fluorine, chlorine, bromine and iodine, perovskites can be assigned properties that are dependent on the chemical composition of the crystal.

LEDs for green and red light have already been created by perovskites, but so far the lack of a single color, blue, makes it impossible to achieve white light.

“Blue light is the key to bringing light-emitting perovskites to practical applications. Our latest step is one step along the way,” said Feng Gao, a professor at the Department of Physics, Chemistry and … Biology at Linköping University.

Feng Gao research group, in collaboration with colleagues in Lund, Britain, Germany, China and Denmark, has created halide perovskites that provide stable emissions in the 451- wave area. 490 nanometers – corresponds to deep blue to the blue colors of the sky. Max Karlsson is a doctoral student at Linköping University and the first author of the now published article Nature Communication. He says:

“Metal-halide perovskites are easily stained over the entire visible spectrum by the use of a simple alloy. Unfortunately, and a blue LED turns green during operation. We have found a way which prevents this color shift by controlling the film crystal dynamics when creating perovskite.These decisions pave the way for stable perovskite alloys, not only for LEDs but also for solar cells. “

The challenge of creating blue light in perovskites is that it requires a chemical composition with a large fraction of chloride, which makes the perovskite unstable. Perovskite-based blue LEDs have previously been created using what is referred to as the “quantum limiting mechanism,” which provides high-intensity LEDs with poor efficiency. However, stable perovskites with the desired chloride level can be created with the help of the “valve-assisted crystallization mechanism.” In addition, researchers at Linköping University have achieved energy efficiencies of up to 11% for the perovskite-based blue LEDs.

“We have shown that halide perovskites-based blue light emitting diodes can be both efficient and stable over a broad spectrum, without the use of quantum limiting. We have developed one of the most efficient perovskite-based blue LEDs. a hitherto well – known creation, “said Weidong Xu, a postdoc at Linköping University.

The science of perovskites is a relatively new field of research that has aroused considerable international interest, as it offers great potential for the development of cheap and effective materials. Feng Gao, however, will quickly say that the work they have done is fundamental research, and claims are still a long way off in the future.

“Perovskite LEDs are a young technology and have a way to go before they see the light of day. Currently, the short life and poor performance of blue LEDs are the main obstacles for perovskite light emitting diodes before for them to start competing with existing technologies such as light emitting diodes based on organic and inorganic semiconductors. We will continue to work on that to make PeLEDs comparable to other technologies, “said Feng Gao.