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).

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Researchers develop a cryogenic process for PSC production without anti-solvents

Researchers from Nazarbayev University in Kazakhstan and Hong Kong Polytechnic University have demonstrated a new 4-step process including (i) spin-coating of the precursors; (ii) cryogenic treatment; (iii) blow-dry process for the removal of the solvent; and (iv) thermal annealing. This process is a straightforward and effective technique which can yield homogenous perovskite films without the use of anti-solvents and regardless of the complexity of the precursor compositions.

Researchers develop a cryogenic process for PSC production without anti-solvents image

When mixed perovskite precursor solutions are evaporated, usually non-uniform films with poor morphology are obtained due to coalescence of perovskite crystallites during rapid solvent removal. Therefore, anti-solvents are usually used to preapare mixed perovskite thin films. However, this technique is not convenient for large-scale manufacturing in industry since the final perovskite film quality critically depends on multiple parameters while adding the anti-solvent. Inaccurate control of the mixing process will cause gradients in over-saturation of the precursor solution, leading to spatially inhomogeneous nucleation of the perovskite and deterioration of the resultant film quality. Furthermore, commonly used anti-solvents such as chlorobenzene or toluene are environmentally harmful and highly toxic. The team's new method circumvents these issues and offers an improved alternative that enhances the control over the perovskite growth process, decoupling the nucleation and crystallization phases.