Chameleon materials: The origin of color variation in low-dimensional perovskites

Phys.org  May 11, 2020 Perovskites ability to emit light over a broad wavelength range is widely attributed to broad luminescence with a large Stokes shift to self-trapped excitons forming due to strong carrier–phonon interactions. Researchers in the Netherlands highlight the extrinsic origin of their broad band emission. As shown by below-gap excitation, in-gap states in the crystal bulk are responsible for the broad emission. This insight advances the understanding of the emission properties of low-dimensional perovskites and question the generality of the attribution of broad band emission in metal halide perovskite and related compounds to self-trapped excitons…read more. Open Access […]

A perovskite-based diode capable of both light emission and detection

Phys.org  April 10, 2020 An international team of researchers (Sweden, China, Italy, Switzerland) has developed an efficient solution-processed perovskite diode that can work in both emission and detection modes. The device can be switched between modes by changing the bias direction, and it exhibits light emission with an external quantum efficiency of over 21% and a light detection limit on a subpicowatt scale. The operation speed for both functions can reach tens of megahertz. The diodes exhibit a high specific detectivity at its peak emission (~804 nm), which allows an optical signal exchange between two identical diodes. To illustrate the potential […]

Scientists create thin films with tantalizing electronic properties

Science Daily  December 23, 2019 An international team of researchers (USA – SUNY New York, Los Alamos National Laboratory, Rensselaer Polytechnic Institute, China) has fabricated barium zirconium sulfide (BaZrS3) thin films by sulfurization of oxide films deposited by pulsed laser deposition. They showed that these films are n-type with carrier densities in the range of 1019-1020 cm−3. Temperature dependent conductivity measurements suggest shallow donor levels. By assuring that BaZrS3 is a promising candidate, these results potentially unleash a family of chalcogenide perovskites for optoelectronics such as photodetectors, photovoltaics, and light emitting diodes…read more. TECHNICAL ARTICLE

Across the spectrum: Researchers find way to stabilize color of light in next-gen material

Science Daily   February 11, 2019 Color tunability has always been possible with halide perovskites, but it’s not been stable. While the bandgap can be conveniently tuned by mixing different halogen ions, mixed-halide perovskites suffer from severe phase separation under illumination. A team of researchers in the US (Florida State University, Rensselaer Polytechnic Institute) found that phase separation can be highly suppressed by embedding nanocrystals of mixed-halide perovskites in an endotaxial matrix. The tuned bandgap remains remarkably stable under extremely intensive illumination. The agreement between the experiments and a nucleation model suggests that the size of the nanocrystals and the host-guest […]

Unleashing perovskites’ potential for solar cells

MIT News  February 7, 2019 Perovskites have attracted a great deal of attention as potential new solar-cell materials because of their low cost, flexibility, and relatively easy manufacturing process. But much remains unknown about the details of their structure and the effects of substituting different metals or other elements within the material. A team of researchers in the US (MIT, UC San Diego, Georgia Institute of Technology, Purdue University, Argonne National Laboratory) found that adding these alkali metals, such as cesium or rubidium, to the perovskite compound helps some of the other constituents to mix together more smoothly making it […]