December 2019

2019 is soon over - and it was and interesting year for the perovskite industry - with some initial signs of commercialization as actual production capacity is being finally built and some novel research activities.

Here are the top 10 stories posted on Perovskite-Info in 2019, ranked by popularity (i.e. how many people read the story):

1. HZB team achieves 21.6% efficiency for perovskite CIGS tandem solar cell (Feb 5)
2. Perovskite-based quantum dots - a guest post by Ossila (Jan 7)
3. DoE announces $130 Million for early-stage solar research project (Mar 27)
4. Researchers reduce reflection losses and reach 25.2% conversion efficiency in perovskite/silicon tandem solar cells (Feb 22)
5. Novel method creates high-quality crystalline and stable FAPbI3 perovskite thin films (Mar 24)
6. Chinese researchers create efficient perovskite-based solar cells using Graphdiyne, a unique carbon material (Jan 10)
7. Perovskite solar cell developer Swift Solar raises $4.6 million (Jan 1)
8. Researchers characterize structural defects in perovskites (Nov 26)
9. Oxford PV raises £31 Million funding (Mar 17)
10. Oxford PV and Meyer Burger enter strategic partnership (Mar 24)

Scientists from the University at Buffalo have created thin films made from barium zirconium sulfide (BaZrS₃), a category of materials known as chalcogenide perovskites, and confirmed that it has impressive electronic and optical properties previously predicted by theorists.

The films reportedly combine exceptionally strong light absorption with good charge transport ' two qualities that make them ideal for applications such as photovoltaics and light-emitting diodes (LEDs).

Researchers from the University of California, San Diego and UCLA, Soochow University and Westlake University in China, and Marmara University in Turkey, have examined the surface defect-deactivation mechanism in perovskite solar cells using molecules found in tea, coffee and chocolate.

The collaborative team set out to delineate the molecular arrangements that constructively deactivate the surface defects in perovskite solar-cells. Highly-efficient metal-halide perovskite solar cells to date consist of polycrystalline perovskite film that often contains a high density of defects on the surface. These imperfections are the points for charge recombination, which is a major limiting factor in power conversion efficiency (PCE) and stability of perovskite solar cells. However, due to the ionic nature of the perovskite lattice, these defects can be passivated by surface treatment of perovskite with a small molecule.

Researchers at the National University of Singapore (NUS) have developed highly efficient, large-area and flexible perovskite-based near-infrared LEDs for new wearable device technologies.

The team, led by Tan Zhi Kuang from the Department of Chemistry and the Solar Energy Research Institute of Singapore (SERIS), has developed high-efficiency near-infrared LEDs which can cover an area of 900 mm² using low-cost solution-processing methods. This is several orders of magnitude larger than the sizes achieved in previous reports, and opens up a range of new applications.

Scientists from the universities of Cambridge and Oxford in the UK are investigating electron dynamics in perovskite solar cells in an effort to understand why such devices demonstrate such impressive conversion efficiency despite their thermal stability and durability problems.

The researchers said the morphology of the perovskite materials used for PV applications was not ideal for understanding the spatiotemporal charge-carrier dynamics which take place within them when photons are absorbed by methylammonium lead-iodide perovskite films.

Researchers from Queen Mary University of London, University College London and Italy's CNR have developed new thermoelectric materials, which could provide a low-cost option for converting heat energy into electricity.

Halide perovskites have been proposed as affordable alternatives to existing thermoelectric materials, however so far research into their suitability for thermoelectric applications has been limited. In this study, the team conducted a series of experiments on thin films of the halide perovskite, caesium tin iodide, to test its ability to create electrical current from heat.

Researchers at the University of Central Florida used Machine Learning (artificial intelligence) to optimize the materials used to make perovskite solar cells (PSC). Perovskites can be difficult to make as a usable and stable material for solar cells. Scientists have been trying to find just the right recipe to make them with all the benefits, and that's where artificial intelligence might come in for the rescue.

The team reviewed more than 2,000 peer-reviewed publications about perovskites and collected more than 300 data points then fed into the AI system they created. The system was able to analyze the information and predict which perovskites recipe would work best.

Researchers from the University of North Carolina have devised a method to rapidly produce large perovskite films for solar cells. The new approach, which combines the right amounts of volatile and less volatile solvents in a blade-coating process, could be an important step towards the commercialization of perovskite solar cells.

The blading process can create perovskite films rapidly to produce much larger devices than ever before. Image source: Yehao Deng et al/Science/AAAS

Although rapid deposition of large-area perovskite films under ambient conditions is an important goal in photovoltaics, rapid crystallization at low temperatures generally results in poor quality films that are not suitable for solar cell applications, so a slow growth and/or high temperatures are commonly used. The new method allows for the deposition of large-area, high-quality perovskite films at 99 mm/s under mild conditions. "We designed a general solvent mixing so that one can blade-coat continuous, large grain and compact perovskite films at unprecedented speed at room temperature in air" says team leader Jinsong Huang of the University of North Carolina.

A team of researchers from Japan's Tokyo Tech have demonstrated perovskites' potential in the production of ammonia directly from hydrogen and nitrogen. This has the potential to open up a new approach to the manufacture of this industrially and agrochemically important gas. Ammonia is used widely an industrial reagent and in the formation of agricultural fertilizers, there are also examples of it being used as a "clean" energy carrier for hydrogen gas for fuel cells.

Masaaki Kitano and his team at Tokyo Tech point out that the main barrier to a facile synthesis of ammonia from hydrogen and nitrogen gas is the surmounting the high energy barrier needed to split diatomic nitrogen. Nitrogen-fixing plants, of course, can handle this process with a range of enzymes evolved over millions of years and metals catalysts coupled with high temperatures and pressures are the mainstays of the industrial process. There have been efforts to make perovskites in which some of their oxygen atoms have been replaced with hydrogen and nitrogen ions to act as ammonia forming materials, but these too only work at a high temperature of more than 800 degrees Celsius and the reaction takes weeks to proceed to completion. These two factors had until now meant perovskites were not looking too promising as a way to create a new ammonia process.

Researchers from Lehigh University in Pennsylvania have found that metal chalcogenide perovskites can be used as a thermoelectric material that can convert thermal energy from the sun to usable electric power.

Metal chalcogenide perovskites, with their nontoxic elemental composition, are known to offer greater thermal and aqueous stability than organic-inorganic halide perovskites. This means that they may be more suitable than other materials in the perovskite family to address the two biggest issues in commercial solar cell production: low thermal stability and toxicity.