Researchers at Linköping University in Sweden have developed efficient blue LEDs based on halide perovskites. The new LEDs could open the door to cheap and energy-efficient illumination.

Schematic of the PeLED structure and the HAADF cross-sectional device image. Image from Nature Communications

Illumination is responsible for approximately 20 percent of global electricity consumption, a figure that could be reduced significantly if all light sources consisted of light-emitting diodes (LEDs). The blue-white LEDs currently in use, however, need complicated manufacturing methods and are expensive, which makes it more difficult to achieve a global transition. LEDs manufactured from halide perovskites could be a cheaper and more eco-friendly alternative for both illumination and LED-based monitors.

Australian scientists at the University of Queensland have designed a perovskite solar cell based on a mix of 2D and 3D salts. By adding a fluorinated lead salt in the processing solution ' normally used to form 3D methylammonium lead iodide ' they were able to achieve a 21.1% efficiency, an open-circuit voltage of 1.12'V, a short-circuit current of 22.4'mA/cm², and a fill factor of 84%.

The scientists stated that the new cell is more moisture-resistant and durable than 'conventional' perovskite cells based on 3D materials alone. The cell is meant to include the advantages of cells based on two-dimensional (2D) perovskites, which generally provide more hydrophobicity and thermal stability than 'conventional' 3D structures. But it should also include the benefits of 3D perovskite cells, which can offer strong light absorption, good charge carrier transport, and higher power conversion efficiencies.

The University of Macau (UM) Institute of Applied Physics and Materials Engineering (IAPME) and Nanjing Tech University jointly developed a method to prepare phase-pure quasi two-dimensional (2D) metal-halide perovskites, which could be used for constructing stable perovskite solar cells.

The very low formation energy of the typically used three-dimensional (3D) perovskites accounts for their low stability and hinders the commercialization of perovskite optoelectronic devices. Recent studies show that the dimensionality of deposited perovskites could be reduced from 3D to quasi 2D by introducing an appropriate amount of long organic cations into the precursor solution, which can greatly improve the stability of perovskites thanks to the protection offered by the organic cation layer on the surface. However, such 2D perovskites typically consist of multiple quantum wells with a random well width distribution because of the thermodynamic stability of compounds in the solution. The thick quantum wells and 3D perovskite within the deposited film will still limit the overall stability of the material. Therefore, the deposition of phase-pure quasi 2D perovskite remains a key scientific challenge.

China-based Zhijing Nanotech develops perovskite-QD film (PQDF) technologies for the display industry, and the company demonstrated its first prototypes in 2018.

Perovskite-Info has talked with the company's management, which updated us that it recently concluded a successful pilot with TCL. TCL, in collaboration with Zhijing Nanotech, produced 500 75-inch QD-enhanced LCD TVs (TCL 4K 75M10) with Zhijing's PQDF films. The company reports that the TVs featured a wide color gamut, 147% BT709 - which is higher than most QD TV's on the market, and higher than TCL's original 75M10 TVs.

An international team of scientists, including ones from King Abdullah University of Science & Technology (KAUST) and University of Toronto, set out to increase the performance of solar panels by creating a bifacial (two-sided) tandem solar cell, made of perovskite and silicon materials.

Image credit: U of T

In outdoor environments, light primarily comes directly from the sun. Conventional tandem solar cells can already convert this light into electricity more efficiently compared to traditional silicon-only solar cells by absorbing additional wavelengths of light. Now, the researchers have realized that even more energy can be gathered using a two-sided tandem configuration. Light reflected and scattered from the ground ' referred to as 'albedo' ' can also be collected to significantly increase the current of a tandem solar cell. The new research outlines how the team engineered the perovskite/silicon device to exceed the currently accepted performance limits for the tandem configuration.

An international group of researchers, led by the University of Padova in Italy, has designed a hole extraction layer with water-splitting additives to reduce the impact of moisture in perovskite solar devices. They reported that the method ensured a power conversion efficiency of more than 9% in perovskite cells stored for a month in a water-saturated atmosphere.

There is an ongoing search for moisture stability in perovskite solar cells (PSCs), as protecting the perovskite layer from moisture is key to preventing excess water from forming on the layer itself and affecting overall performance. The new proposed solution to this issue integrates water-splitting (WS) hydrophobic layers to the perovskite absorber of a standard perovskite cell. The ancillary layers can purportedly convert incoming water into oxygen and hydrogen.

Venture Kick, a private consortium that aims to push forward young entrepreneurs with high-potential business ideas, has selected Perovskia, a nascent perovskite-based solar cells company, to receive CHF40,000 (around USD$45,170).

Perovskia is a young startup that has developed a digital printing technology to fabricate efficient and stable perovskite solar cells with custom design capability. The fabrication techniques they developed are reportedly highly efficient and flexible, which could reduce the production cost considerably, even for customized items. The team plans to use its technology to cater to the diverse needs of Internet of Things, electronic goods, sensors, and ultimately designer solar tiles industries.

A collaboration between University of Pennsylvania, Seoul National University, the Korea Advanced Institute of Science and Technology, the Ecole Polytechnique Fédérale de Lausanne, the University of Tennessee, the University of Cambridge, the Universitat de Valencia, the Harbin Institute of Technology, and the University of Oxford has yielded an understanding of how a class of electroluminescent perovskite materials can be designed to work more efficiently.

This latest work is based on a past endeavor by Penn theoretical chemist Andrew M. Rappe and Tae-Woo Lee at Seoul National University to develop a theory to help explain experimental results. The material that was studied was formamidinium lead bromide, a type of metal-halide perovskite nanocrystal (PNC). Results collected by the Lee group seemed to indicate that green LEDs made with this material were working more efficiently than expected. 'As soon as I saw their data, I was amazed by the correlation between the structural, optical, and light-efficiency results. Something special had to be going on,' says Rappe.

Researchers at the Department of Energy's SLAC National Accelerator Laboratory and Stanford University have used the lab's X-ray laser to watch and directly measure the formation of polarons for the first time. Polarons are fleeting distortions in a material's atomic lattice that form around a moving electron in a few trillionths of a second, then quickly disappear. Despite their transient nature, they do affect a material's behavior, and may even be the reason that solar cells made with lead hybrid perovskites achieve extraordinarily high efficiencies in the lab.

Polaron 'bubbles' of distortion form around charge carriers ' electrons and holes that have been liberated by pulses of light ' which are shown as bright spots here. Image by SLAC

Perovskite materials are famously complex and hard to understand, according to Aaron Lindenberg, an investigator with the Stanford Institute for Materials and Energy Sciences (SIMES) at SLAC and associate professor at Stanford who led the research. While scientists find them exciting because they are both efficient and easy to make, raising the possibility that they could make solar cells cheaper than today's silicon cells, they are also highly unstable, break down when exposed to air and contain lead that has to be kept out of the environment.

Perovskite-Info is happy to announce the 2021 edition of The Perovskite Handbook. This book is a comprehensive guide to perovskite materials, applications and industry. Perovskites are an exciting class of materials that feature a myriad of exciting properties and are considered the future of solar cells, displays, sensors, LEDs and more. The handbook is now updated to January 2021 and lists recent developments and new companies, initiatives and research activities.

Reading this book, you'll learn all about:

• Different perovskite materials, their properties and structure
• How perovskites can be made, tuned and used
• What kinds of applications perovskites may be suitable for
• What the obstacles on the way to a perovskite revolution are
• Perovskite solar cells, their merits and challenges
• The state of the perovskite market, potential and future