New electronic films could enable lightweight night-vision glasses

Amazing stuff! Will we soon be offered smartglasses with this feature? 😊

"As a demonstration, the team fabricated a thin membrane of pyroelectric material — a class of heat-sensing material that produces an electric current in response to changes in temperature. The thinner the pyroelectric material, the better it is at sensing subtle thermal variations.

With their new method, the team fabricated the thinnest pyroelectric membrane yet, measuring 10 nanometers thick, and demonstrated that the film is highly sensitive to heat and radiation across the far-infrared spectrum.

The newly developed film could enable lighter, more portable, and highly accurate far-infrared (IR) sensing devices, with potential applications for night-vision eyewear and autonomous driving in foggy conditions.

Current state-of-the-art far-IR sensors require bulky cooling elements. In contrast, the new pyroelectric thin film requires no cooling and is sensitive to much smaller changes in temperature. The researchers are exploring ways to incorporate the film into lighter, higher-precision night-vision glasses. ...

“remote epitaxy” — a technique where semiconducting materials are grown on a single-crystalline substrate, with an ultrathin layer of graphene in between. The substrate’s crystal structure serves as a scaffold along which the new material can grow. The graphene acts as a nonstick layer, similar to Teflon, making it easy for researchers to peel off the new film and transfer it onto flexible and stacked electronic devices. After peeling off the new film, the underlying substrate can be reused to make additional thin films. ...

discovered that the key to the material’s easy-peel property was lead. As part of its chemical structure ... discovered that the pyroelectric film contains an orderly arrangement of lead atoms that have a large “electron affinity,” meaning that lead attracts electrons and prevents the charge carriers from traveling and connecting to another materials such as an underlying substrate. The lead acts as tiny nonstick units, allowing the material as a whole to peel away, perfectly intact.

The team ran with the realization and fabricated multiple ultrathin films of PMN-PT [Lead Magnesium Niobate-Lead Titanate], each about 10 nanometers thin. They peeled off pyroelectric films and transferred them onto a small chip to form an array of 100 ultrathin heat-sensing pixels, each about 60 square microns (about .006 square centimeters). They exposed the films to ever-slighter changes in temperature and found the pixels were highly sensitive to small changes across the far-infrared spectrum.

The sensitivity of the pyroelectric array is comparable to that of state-of-the-art night-vision devices. These devices are currently based on photodetector materials, in which a change in temperature induces the material’s electrons to jump in energy and briefly cross an energy “band gap,” before settling back into their ground state. This electron jump serves as an electrical signal of the temperature change. However, this signal can be affected by noise in the environment, and to prevent such effects, photodetectors have to also include cooling devices that bring the instruments down to liquid nitrogen temperatures. ...

The researchers also found that the films were sensitive beyond the range of current night-vision devices and could respond to wavelengths across the entire infrared spectrum. ..."

From the abstract:

"Recent breakthroughs in ultrathin, single-crystalline, freestanding complex oxide systems have sparked industry interest in their potential for next-generation commercial devices. However, the mass production of these ultrathin complex oxide membranes has been hindered by the challenging requirement of inserting an artificial release layer between the epilayers and substrates.

Here we introduce a technique that achieves atomic precision lift-off of ultrathin membranes without artificial release layers to facilitate the high-throughput production of scalable, ultrathin, freestanding perovskite systems.

Leveraging both theoretical insights and empirical evidence, we have identified the pivotal role of lead in weakening the interface.

This insight has led to the creation of a universal exfoliation strategy that enables the production of diverse ultrathin perovskite membranes less than 10 nm. Our pyroelectric membranes demonstrate a record-high pyroelectric coefficient of 1.76 × 10−2 C m−2 K−1, attributed to their exceptionally low thickness and freestanding nature.

Moreover, this method offers an approach to manufacturing cooling-free detectors that can cover the full far-infrared spectrum, marking a notable advancement in detector technology."

New electronic “skin” could enable lightweight night-vision glasses | MIT News | Massachusetts Institute of Technology "MIT engineers developed ultrathin electronic films that sense heat and other signals, and could reduce the bulk of conventional goggles and scopes."

Atomic lift-off of epitaxial membranes for cooling-free infrared detection (no public access)

A major advance in creating a tuneable high-quality thin film chalcogenide perovskites

Recommendable!

"MIT engineers report creating the first high-quality thin films of a new family of semiconductor materials. ...
Chalcogenide perovskites were made as early as the 1950s by French chemists. Similar work was repeated in the 80s and early 90s, but “the idea that these materials would be useful semiconductors didn’t come along until the early 2010s ...

Jaramillo and colleagues used a technique called molecular beam epitaxy (MBE) to grow their high-quality films. The technique allows atomic-level control over crystal growth ... 

As its name implies, MBE essentially points beams of molecules at a specific arrangement of atoms on a surface (“taxy,” as in epitaxy, means arrangement, or orientation). That arrangement of atoms provides a template for the beamed molecules to grow on. “That’s why epitaxial growth gives you the highest-quality films. The materials know how to grow,” ..."

From the abstract:

"The making of BaZrS3 thin films by molecular beam epitaxy (MBE) is demonstrated. BaZrS3 forms in the orthorhombic distorted-perovskite structure with corner-sharing ZrS6 octahedra. The single-step MBE process results in films smooth on the atomic scale, with near-perfect BaZrS3 stoichiometry and an atomically sharp interface with the LaAlO3 substrate. The films grow epitaxially via two competing growth modes: buffered epitaxy, with a self-assembled interface layer that relieves the epitaxial strain, and direct epitaxy, with rotated-cube-on-cube growth that accommodates the large lattice constant mismatch between the oxide and the sulfide perovskites. This work sets the stage for developing chalcogenide perovskites as a family of semiconductor alloys with properties that can be tuned with strain and composition in high-quality epitaxial thin films, as has been long-established for other systems including Si-Ge, III-Vs, and II-VIs. ..."

Engineers report a major advance in creating a new family of semiconductor materials | MIT News | Massachusetts Institute of Technology Ultrastable and made of inexpensive, nontoxic elements, chalcogenide perovskites could find applications in solar cells, lighting, and more.

Making BaZrS3 Chalcogenide Perovskite Thin Films by Molecular Beam Epitaxy (no public access)

New record efficiency for flexible perovskite solar cells

Does it matter that perovskite is now 20.7% efficient? Who are they trying to fool?

How many 1000 square meters of land do you need to replace a typical nuclear power plant? 

How often do you need to clean solar power panels to maintain high efficiency?
And so on ..

New record efficiency for flexible perovskite solar cells | Research | Chemistry World (behind paywall) Porous planar electron transport layer boosts power conversion efficiency in flexible perovskite solar cells to 20.7%

Perovskite Is No Miracle Material

Posted: 1/8/2015

Trigger

Just read “Perovskite solar cell reaches record efficiency”. There have been lots of articles lately about the miracles achieved with Perovskite.

By The Way

At least this article mentions:

1. “[P]erovskite based materials are water soluble which is a serious concern for solar cells that will be exposed to the elements.”
2. “Also, there is the problem of scaling, the cells being tested were just 0.1cm2.”
3. “And then there is the well known issue of hysteresis, where the material sometimes appears to change when first exposed to sunlight, causing a drop in efficiency. ”