Technical / research - Page 58

Researchers at the Indian Institute of Technology Madras (IIT-M) have developed a perovskite-based white light emitter for use in energy-efficient Light Emitting Diodes or LEDs.

As conventional LED materials cannot emit white light, to produce white light, specialized techniques such as coating blue LED with yellow phosphor and combining blue, green, and red LEDs have been used, along with a worldwide search for materials that can directly emit white light.

The US Department of Energy (DoE) awarded nearly $40 Million for grid-decarbonizing solar technologies projects. The DoE awarded the funds to 40 research projects, several of which are perovskite related. We'll list the perovskite projects (which were awarded a total of $1.25 million) below.

The DoE also issued a request for information (RFI) to gather input on efficiency, stability and replicability performance targets for perovskite photovoltaic devices that could be utilized to demonstrate technical and commercial readiness for future funding programs.

Unlike the narrow band emission based on free excitons in lead-perovskite nanocrystals (NCs), the low electronic dimensionality in lead-free double perovskite NCs can lead to self-trapped excitons (STEs), generating a broadband emission. To date, how the singlet/triplet STEs influence the photoluminescence properties and whether triplet STEs can generate efficient emission in double-perovskite NCs has been unclear.

A research team, led by Prof. Han Keli and Yang Bin from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences, recently synthesized double perovskite nanocrystals with bright photoluminescence emission based on triplet STEs.

Scientists at MIT recently reported creating the first high-quality thin films of a new family of semiconductor materials - chalcogenide perovskites. This achievement, lead by MIT researcher Rafael Jaramillo, has the potential to impact multiple fields of technology.

Chalcogenide perovskites could have applications in solar cells and lighting, Jaramillo says. He notes, however, that "the history of semiconductor research shows that new families of semiconductors are generally enabling in ways that are not predictable."

Researchers at UC Santa Barbara recently conducted a research that disproved the common belief that organic molecules are crucial to achieving PSCs' impressive performance because they suppress defect-assisted carrier recombination. Not only was this assumption shown to be incorrect, but the team also found that all-inorganic materials have the potential for outperforming hybrid perovskites.

“To compare the materials, we performed comprehensive simulations of the recombination mechanisms,” explained Xie Zhang, lead researcher on the study. “When light shines on a solar-cell material, the photo-generated carriers generate a current; recombination at defects destroys some of those carriers and hence lowers the efficiency. Defects thus act as efficiency killers.”

A team of researchers from HZB, CNRS and Charles University used a multi-method approach to quantify and characterize defects in single crystal MAPbI₃, giving a cross-checked overview of their properties. The team characterized five different defect types and measured the interaction between these defects and the charge carriers.

MAPI semiconductors consist of organic methylammonium cations and lead iodide octahedra that form a perovskite structure. MAPI based solar cells have achieved efficiencies of 25% within a few years. But so far, the semi-organic semiconductors are still ageing rapidly.

Researchers at the University of Rome Tor Vergata's Centre for Hybrid and Organic Solar Energy (CHOSE) and ISM-CNR have tested a commercially available HTM with a new core made by low-cost fluorene'xantene units. The experimentation was conducted on small (0.09 cm²) and large area (1.01 cm²) cells.

The one-pot synthesis of this compound is said to drastically reduce its cost compared with the commonly used Spiro-OMeTAD. The optoelectronic performances and properties were characterized through JV measurement, IPCE (incident photon to current efficiency), steady-state photoluminescence and ISOS stability test. SEM (scanning electron microscope) images reveal a uniform and pinhole free coverage of the X55 HTM surface, which reduces the charge recombination losses and improves the device performance relatively to Spiro-OMeTAD from 16% to 17%. The ISOS-D-1 stability test on large area cells without any encapsulation reports an efficiency drop of about 15% after 1000 h compared to 30% for the reference case.

Researchers from the University of Surrey, University of Cambridge and University of Toronto, have explained the origin, characterization, pitfalls and opportunities for strain in perovskite materials. The team also explained their vision of how the research community can use strain to unleash the full potential of perovskite materials.

Dr. Wei Zhang, a corresponding author and Senior Lecturer from the University of Surrey, said: "Many in the photovoltaic research community are rightly excited about the potential of perovskite materials, not only when it comes to green technologies such as solar cells but other electronic devices. In this study, we look at factors that influence the efficiency and stability of devices'and explore the role strain may play on perovskites. A comprehensive understanding of strain in perovskites will lead to perovskite materials with remarkable optoelectronic novelty."

A team of researchers from the Indian Institute of Technology Bhilai has developed a perovskite solar cell with an active area of 2cm² and a back contact electrode made of copper (Cu). The team's new work utilized copper contacts instead of gold for reduction of costs.

The solar cell was fabricated via a two-step spin-coating technique with a fluorine-doped tin oxide (FTO) substrate; a methylammonium lead iodide (MAPbI₃) perovskite layer sandwiched between a titanium oxide (TiO₂) electron transport layer (ETL) and a hole transport layer (HTL) made of Spiro-OMeTA; and a copper conducting electrode. A similar device with a gold (Au) conducting electrode was also built, as a reference cell. 'Copper or gold contact electrodes were deposited through a metal shadow mask by thermal evaporation to complete the cell fabrication process,' the research group said.

A team of researchers from Oak Ridge National Laboratory, Florida State University, Argonne National Laboratory, University of Pittsburgh, Pittsburgh Quantum Institute and Sungkyunkwan University has found a rare quantum material in which electrons move in coordinated ways, essentially 'dancing.'

Straining the material creates an electronic band structure that sets the stage for exotic, more tightly correlated behavior ' similar to tangoing ' among Dirac electrons, which are especially mobile electric charge carriers that may someday enable faster transistors.