Perovskite LED - Page 14

Researchers from ITMO University, along with colleagues from Sweden, Australia, the United States and Lithuania, have discovered Fano resonance in perovskite nanoparticles and gained control over the resonance spectrum for an array of inorganic nanoparticles. This newly designed method reversibly adjusts the radiation color of nanosized light sources. Previously, radiation color could be specified only during nanoparticle synthesis, but now it can be changed after synthesis. Stability and electromagnetic resonances of the particles are retained during this adjustment. This makes them promising for optical chips, LEDs and optoelectronic devices.

Resonance is the coincidence between frequencies of two oscillations increasing their intensity. A half-century ago, the Italian theoretical physicist Hugo Fano described a special type of resonance with an asymmetric profile arising from the interference of two wave processes. Since then, Fano resonance has been actively used in photonics, for example, to create fast optical switches. The reduction of such switches to nanoscale will dramatically increase the performance of photonic chips by integrating a huge number of elements in one device.

Researchers at AMOLF have found a way of turning calcium carbonate structures, such as a sea urchin skeleton, into perovskite materials, by modifying the composition of the material. The team explained that "the experiment involves no more than dripping two liquids over the calcium carbonate structure. The conversion is complete within a couple of minutes. If you shine a UV lamp on the structure, you can see the conversion taking place in front of your eyes: The sea urchin skeleton, which initially appears blue under the lamp, changes into a bright green structure with each drop".

A sand dollar skeleton gradually converting into a light emitting perovskite

The researchers estimate that the perovskite microstructures made in this process result in more stable materials. They therefore state that solar cells made from this material should last longer. "In addition, we can produce perovskite structures in every desired color. This means that the material could also be used for LEDs in various applications, such as screens," says the research team.

A team of researchers led by Professor Biwu Ma from Florida State University demonstrated a new approach to building efficient and spectrally stable red perovskite LEDs. The team developed a simple solution processing method followed by thermal annealing to prepare highly luminescent ultra-smooth polymer'perovskite composite thin films with tunable emissions from red to deep-red.

Light emitting diodes (LEDs) incorporating inorganic, organic, or nanoscale materials are highly promising for solid-state lighting and displays. Despite the significant progress achieved in green emitting perovskite LEDs in recent years, blue or red emitting LEDs still remain a challenge with regards to their performance and spectral stability during operation.

A new international study led by chemists at the Georgia Institute of Technology has observed that hybrid organic-inorganic perovskites (HOIPs) possessed a 'richness' of semiconducting physics created by what could be described as electrons "dancing" on wobbling chemical underpinnings. That contradicts established semiconductors that rely upon rigidly stable chemical foundations, or quieter molecular frameworks, to produce the desired quantum properties. This could mean that HOIPs may be used in the future as semiconductors with nuanced colors emanating from lasers, lamps, and even window glass.

HOIPs have been reported by the team to be quite challenging to examine, but the researchers from a total of five research institutes in four countries succeeded in measuring a prototypical HOIP and found its quantum properties on par with those of established, molecularly rigid semiconductors, many of which are graphene-based. 'We don't know yet how it works to have these stable quantum properties in this intense molecular motion,' said first author Felix Thouin, a graduate research assistant at Georgia Tech. 'It defies physics models we have to try to explain it. It's like we need some new physics.'

Researchers from the Russian ITMO University have developed effective nanoscale light sources based on a halide perovskite. These nanosources are subwavelength nanoparticles which serve both as emitters and nanoantennas and allow enhancing light emission inherently without additional devices. Moreover, the perovskite enables tuning the emission spectra throughout a visible range by varying the composition of the material. The new nanoparticles are a promising platform for creating compact optoelectronic devices such as optical chips, light-emitting diodes, or sensors.

The nanoscale light sources and nanoantennas have already found a wide range of applications in several areas, such as ultra compact pixels, optical detection, or telecommunications. However, the fabrication of nanostructure-based devices is rather complicated due to the limited luminescence efficiency of the materials used typically as well as non-directional and relatively weak light emission of single quantum dots or molecules. An even more challenging task is placing a nanoscale light source precisely near a nanoantenna.

Researchers at the U.S. Naval Research Laboratory (NRL) Center for Computational Materials Science, working with an international team of physicists, have found that nanocrystals made of cesium lead halide perovskites (CsPbX3), is the first discovered material which the ground exciton state is "bright," making it an attractive candidate for more efficient solid-state lasers and light emitting diodes (LEDs).

The work focused on lead halide perovskites with three different compositions, including chlorine, bromine, and iodine. Nanocrystals made of these compounds and their alloys can be tuned to emit light at wavelengths that span the entire visible range, while retaining the fast light emission that gives them their superior performance.

Researchers at Duke University have developed a method to create otherwise unattainable (or extremely hard to create) hybrid thin-film materials. The new technique could open the door to new generations of solar cells, light-emitting diodes and photodetectors.

The most common perovskite used in solar energy today, methylammonium lead iodide (MAPbI3), can convert light to energy as well as today's best commercially available solar panels. This can even be done using a fraction of the material - a piece 100 times thinner than a typical silicon-based solar cell. Methylammonium lead iodide is one of the few perovskites that can be created using standard industry production techniques, though it still has issues with scalability and durability. To truly unlock the potential of perovskites, however, new manufacturing methods are needed because the mixture of organic and inorganic molecules in a complex crystalline structure can be difficult to make. Organic elements are particularly delicate, but are critical to the hybrid material's ability to absorb and emit light effectively.

Fuji Pigment recently reported that it is researching and developing a new type of perovskite quantum dots. Fuji stated that the half width of their emission spectra is substantially narrower than that of InP; this property could very beneficial to the application of the dots in display materials, LED, bio-imaging and more.

emission spectra of perovskite quantum dots under 420 nm of irradiation light

The chemical composition of perovskite quantum dots are either CsPbX3 or CH3NH3PbX3 (X= Cl, Br, I). Their quantum efficiency is 50'80 % and their half width is 15'39 nm. Their base solvent is either hexane or toluene. However, finding alternative solvents is a challenge that is now being addressed.

EPFL researchers have designed a new type of inorganic nanocomposite that makes perovskite quantum dots (nanometer-sized semiconducting materials with unique optical properties) exceptionally stable against exposure to air, sunlight, heat, and water.

Quantum dots made from perovskites have already been shown to hold potential for solar panels, LEDs and laser technologies. However, perovskite quantum dots have major issues with stability when exposed to air, heat, light, and water. The EPFL team has now succeeded in building perovskite quantum dot films with a technique that helps them overcome these weaknesses.

Researchers at Los Alamos National Laboratory and their partners are creating innovative 2D layered hybrid perovskites that they say can allow greater freedom in designing and fabricating efficient optoelectronic devices. Industrial and consumer applications could include low cost solar cells, LEDs, laser diodes, detectors, and other nano-optoelectronic devices.

They explain that these materials are layered compounds, or a stack of 2D layers of perovskites with nanometer thickness (like a stack of sheets), and the 2D perovskite layers are separated by thin organic layers. "This work could overturn conventional wisdom on the limitations of device designs based on layered perovskites", the team says.