Researchers settle debate over Rashba Effect in perovskite materials

Scientists have theorized that organometallic halide perovskites are so promising due to a highly controversial mechanism called the Rashba effect. Scientists at the U.S. Department of Energy’s Ames Laboratory have now experimentally proven the existence of the effect in bulk perovskites, using short microwave bursts of light to both produce and then record a rhythm, much like music, of the quantum coupled motion of atoms and electrons in these materials.

Research thus far hypothesized that the materials’ extraordinary electronic, magnetic and optical properties are related to the Rashba effect, a mechanism that controls the magnetic and electronic structure and charge carrier lifetimes. But despite intense study and debate, conclusive evidence of Rashba effects in bulk organometallic halide perovskites, used in the most efficient perovskite solar cells, remained highly elusive.

X-rays reveal in situ crystal growth of lead-free perovskite solar panel materials

University of Groningen scientists are investigating in situ how lead-free perovskite crystals form and how the crystal structure affects the functioning of the solar cells, as part of their quest to find alternatives to lead-based perovskites.

The best results in solar cells have been obtained using perovskites with lead as the central cation. As this metal is toxic, tin-based alternatives have been developed, for example, formamidinium tin iodide (FASnI3). This is a promising material; however, it lacks the stability of some of the lead-based materials. Attempts have been made to mix the 3D FASnI3 crystals with layered materials, containing the organic cation phenylethylammonium (PEA). "My colleague, Professor Maria Loi, and her research team showed that adding a small amount of this PEA produces a more stable and efficient material," says Assistant Professor Giuseppe Portale. "However, adding a lot of it reduces the photovoltaic efficiency".

Israeli researchers examine the self-healing properties of halide perovskites

Researchers at the Weizmann Institute of Science have found that in halide perovskites, creating defects takes more effort than restoring order. This finding may explain the remarkable properties of halide perovskites and help develop a new approach to controlling the properties of these and other materials.

Much about Halide perovskites still puzzles researchers; in particular, it has been unclear why they can contain relatively few defects, on the order of 1010 per cubic centimeter (that is, one defect for every trillion atoms, instead of the one to a hundred for every million, as in regular semiconductors). This concentration of defects rivals that of germanium crystals, among the cleanest solid-state man-made materials. Getting close to such a low defect concentration in the semiconductors used in today’s electronic devices requires enormous effort and ingenuity. In contrast, halide perovskites can be produced within a fraction of a second by mixing simple chemical salt solutions at near room temperature.

New process yields oxide perovskite crystals in flexible, free-standing layers

Researchers at the University of California, Irvine and other institutions have developed a new process for producing oxide perovskite crystals in flexible, free-standing layers.

“Through our successful fabrication of ultrathin perovskite oxides down to the monolayer limit, we’ve created a new class of two-dimensional materials,” said co-author Xiaoqing Pan, professor of materials science & engineering at UCI. “Since these crystals have strongly correlated effects, we anticipate they will exhibit qualities similar to graphene that will be foundational to next-generation energy and information technologies.”

Researchers demonstrate high light extraction efficiency of perovskite photonic crystals

Researchers at NTU, lead by Assoc. Prof. Wang Hong, recently demonstrated high light extraction efficiency of perovskite photonic crystals fabricated by delicate electron-beam lithography.

Researchers demonstrate high light extraction efficiency of perovskite photonic crystals image

The perovskite photonic crystals exhibit both emission rate inhibition and light energy redistribution simultaneously. They observed 7.9-fold reduction of spontaneous emission rate with a slower decay in perovskite photonic crystals due to photonic bandgap effect (PBG).