Perovskites are materials that share a crystal structure similar to the mineral called perovskite, which consists of calcium titanium oxide (CaTiO3).
Depending on which atoms/molecules are used in the structure, perovskites can possess an impressive array of interesting properties including superconductivity, ferroelectricity, charge ordering, spin dependent transport and much more. Perovskites therefore hold exciting opportunities for physicists, chemists and material scientists.
Lasers are devices that stimulate atoms or molecules to emit light at particular wavelengths and amplify that light, typically producing a very narrow beam of radiation. The emission usually focuses on an extremely limited range of visible, infrared, or ultraviolet wavelengths.Laser is an acronym for “light amplification by the stimulated emission of radiation”. Lasers are used in extremely diverse industries and applications, like optical disk drives, laser printers, barcode scanners, DNA sequencing instruments, fiber-optics, laser surgery and other medical applications, military and law enforcement devices and much more.
As direct bandgap semiconductors, perovskites exhibit the unique optical properties of bandgap tunability, charge-carrier mobility, defect tolerance, photoluminescence quantum efficiency and power conversion efficiency. These properties make them promising light-emitting materials for high optical gain, low-threshold and multicolor laser applications. The fact that they can be fabricated from low-cost precursors via simple processes makes them attractive as well.
Lower dimensionality perovskite materials, like nanoplatelets, dots, disks, wires etc., can be tailored to be highly desirable for controlled lasing because of their optical cavities and feedback architectures.
Despite their promising features, there are several challenges, for example low exciton binding energy, environmental stability, and formation of trap states at the vicinity of grain interfaces, that need to be addressed when considering perovskite use in lasers. In that respect, 2D perovskites and triple/mixed cation perovskites appear to have potential.
The latest Perovskite lasers news:
Researchers from Penn State and Princeton University have made strides in creating a diode laser based on a perovskite material that can be deposited from solution on a laboratory benchtop.
Organic diode lasers, that are extremely hard to make, are sought after since they have many advantages. First, because organic semiconductors are relatively soft and flexible, organic lasers could be incorporated into new form factors not possible for their inorganic counterparts. While inorganic semiconductor lasers are relatively limited in the wavelengths, or colors, of light they emit, an organic laser can produce any wavelength a chemist cares to synthesize in the lab by tailoring the structure of the organic molecules. This tunability could be very useful in applications ranging from medical diagnostics to environmental sensing.
Researchers from KU Leuven from the Roeffaers Lab and the Hofkens Group have discovered a new way to create the sought-after dark alpha-phase perovskite. They used direct laser writing (tuned intense laser light) to locally heat the perovskite surface, making it change from the (useless) delta state to the (highly desirable) alpha state.
Furthermore, they also found that the material now remained in this state for many weeks, even at room temperature, without further need of a stabilizing treatment. The scientists further managed to use the laser beam to rapidly micro-fabricate complex patterns of the dark FAPbI3 state. "These findings are a big step forward in locally tailoring the structural, electrical, and optical properties of an important new class of materials and provides an avenue for making customised optical devices, all on demand".
Researchers at the Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) have demonstrated that halide perovskites are capable of discharging multiple, bright colors from just one nanowire at resolutions as small as 500 nm. This work could impact the development of new applications in optoelectronics, nanoscopic lasers, photovoltaics and more.
The team used electron beam lithography to fabricate halide perovskite nanowire heterojunctions, the junction of two types of semiconductors. The researchers analyzed cesium lead halide perovskite, and then used a common nanofabrication method integrated with anion exchange chemistry to switch out the halide ions to form cesium lead bromide, cesium lead iodide and cesium lead chloride perovskites. Each difference resulted in a different color discharged.
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.
Researchers at Nanyang Technological University in Singapore have fabricated high-performance green light-emitting diodes based on colloidal organometal perovskite nanoparticles. The devices have a maximum luminous efficiency of 11.49 cd/A, a power efficiency of 7.84 lm/W and an external quantum efficiency of 3.8%. This value is said to be about 3.5 times higher than that of the best colloidal perovskite quantum-dot-based LEDs previously made.
The team developed a simple way to make a series of colloidal (CH3NH3)PbX3 nanoparticles with an amorphous structure that can be tuned to emit light in the ultraviolet to near-infrared range. They studied the photoluminescence properties of the nanoparticles and found that the PLQE of the perovskite NP film is much higher than that of the bulk film. They then made the highly efficient green LED.
Researchers from the King Abdullah University of Science and Technology (KAUST) have designed a system that uses an innovative color converter based on luminescent materials known as phosphors, which are commonly used in LED lights, and combines them with nanocrystals of perovskite. This system has achieved record bandwidth, providing a data transmission rate of 2Gbit per second.
The major achievements in this work are breaking the record for data communication using visible light and, even more impressively, producing white light with a very high color-rendering index of 89, by designing a special color converter based on hybrid perovskite nanocrystals. The work demonstrates white light as both a lighting source and a system for ultra-high-speed data communications.
Scientists at Syracuse University and Brookhaven National Laboratory found a new way to visualize and monitor chemical reactions in real time using perovskites. They have designed a nanomaterial that changes color when it interacts with ions and other small molecules during a chemical reaction, allowing to monitor reactions qualitatively with the naked eye and quantitatively with simple instrumentation.
The researchers explain that many chemical reactions occur in a solution that is colorless and transparent so the only way to know if a reaction has occurred or not is to perform extensive analysis after a multi-step purification. This new method represents a simpler way to investigate why and how fast a reaction occurs (if at all). The group has designed a nanoparticle that reacts with by-products of the reaction. When the reaction occurs, the nanoparticle fluoresces at a different color, allowing to gauge kinetics by eye, instead of using special equipment.
Researchers at the University of California at Berkeley and the Lawrence Berkeley National Lab have made novel high-performance and robust lasers from caesium lead halide perovskites nanowires, that could be used in on-chip photonic and spectroscopic applications, such as optical communications, imaging and sensing. The lasing color of the devices can also easily be tuned from green to blue by changing the halide ion.
Nanowire lasers show great promise as miniaturized light sources for optoelectronics. Since they act as both the laser cavity and gain medium, nanowires can be easily incorporated into electronic circuits. Optical gain is the ability of a material to 'amplify' light or to generate more photons than the number of photons it absorbs. A typical laser usually consists of a gain medium encased in an optical cavity containing two opposing mirrors. The gain medium contains two electronic energy levels, and the lower energy level naturally contains more electrons than the upper level. However, by exciting the cavity ' either electrically or by using light ' some electrons can be 'pumped' into the upper state.
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.