October 2017

Researchers at the National Renewable Energy Laboratory (NREL) and the University of Washington have designed an interesting strategy for driving down the cost of solar cells while ramping up efficiency: the team developed a high cost, high efficiency quantum dot solar cell for space applications, and provided the expensive solar cell up with a cheaper perovskite layer. The combined solar cell would be aimed at terrestrial applications with a more moderate price point. Note that in the proposed lower cost solar cell, the cheap layer is not the only role for perovskite. The expensive quantum dot layer would also be made of perovskite.

The NREL team explains that colloidal quantum dots are electronic materials and because of their astonishingly small size (typically 3-20 nanometers in dimension) they possess fascinating optical properties. That first quantum dot solar cell had a conversion efficiency of just 2.9% and was based on a lead sulfide formula. Things moved along quickly after that, and NREL noted a record of 12% for lead sulfide achieved by the University of Toronto just last year.

A recent study, affiliated with UNIST and the Korea Institute of Energy Research (KIER),has shown a highly stable perovskite solar cells (PSCs), using edged-selectively fluorine (F) functionalized graphene nano-platelets (EFGnPs). This breakthrough is interesting since it is made out of fluorine, a low-cost alternative to gold.

To tackle the issue of perovskite materials' sensitivity to moisture and make progress toward the commercialization of PSCs, the team introduced a highly stable p-i-n structure for PSCs using fluorine functionalized EFGnPs to fully cover the perovskite active layer and protect against the ingress of water for high-stability PSCs.

Two studies led by teams at the Department of Energy's Oak Ridge National Laboratory have shown that treating a complex oxide crystal with either heat or chemicals caused different atoms to segregate on the surface (surface reconstruction) - creating catalysts with dissimilar behaviors ultimately yielding distinct products. This technique may enable catalyst designers to drive industrially important chemical reactions to improve yields of desired products and reduce unwanted products so post-reaction separation costs can be significantly diminished.

The researchers surveyed four perovskite catalysts. The tests showed that treating a perovskite with heat resulted in a catalyst with more A atoms on its surface, while treating the same perovskite with chemicals instead produced more B atoms on the surface.

Researchers from Italy's University of Florence have found that graphene could significantly improve the efficiency of perovskite solar cells. The researchers have shown how the introduction of graphene and graphene oxide doped with lithium atoms (GO-Li) into a perovskite-based cell may increase its conversion efficiency, as both the carrier recombination dynamics and the defect density of the perovskite are considerably improved.

The scientists used graphene doped mesoporous TiO2 (G+mTiO2) with the addition of a lithium-neutralized graphene oxide (GO-Li) interlayer as ETL. They found that the carrier collection efficiency is increased by about a factor two with respect to standard mTiO2.

The Riken research institute in Japan recently announced that it has found a new candidate material for perovskite solar cells, by using the "K" supercomputer to carry out a search based on high-efficiency material screening.

The supercomputer enables running simulations in which elements of a well-known compound are replaced with different elements to theoretically design a compound with new functions prior to an experiment. This technology can be used, for example, for finding suitable replacements for compounds that are toxic due to lead like methylammonium-lead-iodine and formamidine-lead-iodine.

Researchers from Samsung and Sungkyunkwan University announced that it has developed a new perovskite-based technology for X-ray machines that can cut radiation exposure by 90%. Samsung said that the new X-ray system comes with better sensitivity and is capable of collecting data while exposing patients to less radiation.

The commercialization of the technology may pave the way for the creation of X-ray devices that can scan full bodies, as previous methods had limitations the size of detectors. "If we overcome the remaining technological hurdles," Samsung said, "it could lead to advances in X-ray medical imaging technology that cuts radiation exposure to one tenth that of existing machines".

Scientists at the U.S. Department of Energy's (DOE) Argonne National Laboratory, in collaboration with Brookhaven National Laboratory and three universities, have conducted a study that combined supercomputer simulation and X-ray characterization of a unique peroskite material that gradually "forgets", like the human brain, and could one day be used for advanced bio-inspired computing.

The material in the study, called a quantum perovskite, offers researchers a simpler non-biological model of what "forgetfulness" might look like on an electronic level. The perovskite shows an adaptive response when protons are repeatedly inserted and removed that resembles the brain's desensitization to a recurring stimulus.

Researchers at the Oak Ridge National Laboratory in the US have developed a new technique for high speed voltage measurements at the atomic level using machine learning. The technique has reportedly been used for mapping surface voltage dynamics of a perovskite solar cell for the first time.

Atomic force microscopy can usually investigate slow or static material structures and functions. In AFM, a rastering probe maps a material's surface and captures physical and chemical properties but the probe is slow to respond to what it detects. Instead, the ORNL team created a fast free force recovery technique that uses advanced machine learning algorithms to analyze instantaneous tip motion to produce high-resolution images 3,500 times faster than standard AFM detection methods.

Researchers from KU Leuven from the Roeffaers Lab and the Hofkens Group have discovered a new way to create the sought-after dark alpha-phase perovskite. They used direct laser writing (tuned intense laser light) to locally heat the perovskite surface, making it change from the (useless) delta state to the (highly desirable) alpha state.

Furthermore, they also found that the material now remained in this state for many weeks, even at room temperature, without further need of a stabilizing treatment. The scientists further managed to use the laser beam to rapidly micro-fabricate complex patterns of the dark FAPbI3 state. "These findings are a big step forward in locally tailoring the structural, electrical, and optical properties of an important new class of materials and provides an avenue for making customised optical devices, all on demand".

Researchers from Lomonosov Moscow State University in Russia explained how changing the ratio of components forming the light-absorbing layer of a perovskite solar cell influences the structure of created films and battery efficiency.

Perovskites can be used to create perovskite solar batteries, which are a relatively new area of R&D, but are showing promise in terms of efficiency and function. In their previous work, the researchers found out that filiform (wire-like) hybrids of perovskites have acquired their shape because of the structure of intermediate compounds, which are formed during the process of perovskite crystallization. The team has discovered a whole group of these compounds, every one of which is a crystalline solvate. The crystalline solvates are crystalline compounds with the molecules of the precursor components' solvent built into their structure. The dissolved components precipitate from the solution and form a crystalline film of perovskite.