April 2016

Researchers at the Department of Energy's Oak Ridge National Laboratory (ORNL) have found a potential way to further improve solar cell efficiency by understanding the competition among halogen atoms during the synthesis of sunlight-absorbing crystals.

Using high-powered imaging techniques, the team tracked kinetic activity in organometallic halide perovskites. Halogen ions, competing for a position in the growing structure, affect the movement of charges through the crystals and subsequently impact the efficiency of sunlight's conversion to electricity.

Stanford University scientists have found that applying pressure can change the properties of perovskites and the way they respond to light. The results of their study suggest that it is possible to increase the voltages of perovskite solar cells by applying external pressure. The researchers also observed a dramatic increase in the electronic conductivity of these materials at high pressures.

To understand exactly how perovskites behave under pressure, the scientists placed the crystals in a vice between two diamonds. As the diamonds were squeezed closer together, the perovskite samples changed color. These lab results indicate that perovskites can absorb high or low energy light waves, depending on the precise amount of pressure that is applied.

IDTechEx recently stated that despite strong enthusiasm last year, there are few companies developing Perovskite PV devices and the topic barely registers in most mainstream press. Despite this somewhat bleak view, IDTechEx claims that much is happening behind the scenes.

According to IDTechEx, most of the effort has been concentrated on materials development -improving stability while maximizing efficiency and, in some cases, creating lead free versions. This will take time, with IDTechEx Research anticipating that the first products will be hybrid silicon-perovskite PV systems creating a market of over $200 million in 2025.

A recent market report by Lux Research stated that perovskites offer several new opportunities for partnerships with universities ahead of a likely commercial deployment between 2019 and 2021. While efficiency of perovskite-based solar cells is constantly improving, the main remaining issues are stability, cost, and the feasibility of real-world efficiencies that must be addressed before commercialization can occur.

Lux Research analysts evaluated the existing state of perovskite solar cells and identified opportunities for companies to partner with academia. Among their findings are the following: partnerships are continuously emerging from labs, and opportunities are still available. Many leading researchers have clear partnerships, but opportunities are still present with various institutions and universities. Also, China is the leading publisher on perovskite solar cells, accounting for a quarter of all academic publications, but more impactful research is coming out of Israel, Switzerland, Singapore, and the UK. China is followed by the USA and South Korea. However, European countries ' the UK, Italy, Switzerland, Germany, Spain, Sweden, France, Greece and Belgium - together account for 24% (almost equivalent to China).

A team of researchers from the National University of Science and Technology (MISIS) in Moscow, in cooperation with colleagues from the University of Texas at Dallas, have developed a flexible solar battery which is said to be at least three times cheaper than its silicon analogues.

The scientists created a perovskite-based thin-filmed photoelectric cell, which made it possible to create an advanced solar battery. According to the tram, the achievement was made possible by the fact that the selected perovskites can convert solar energy radiation into electric energy with a performance coefficient of more than 15%, and with a planned rate of 20%.

Researchers at the Hong Kong Polytechnic University (PolyU) have reported reaching 25.5% efficiency with a perovskite-silicon tandem solar cell. In the tandem cell, a perovskite solar cell is placed on top so that it can harvest the short wavelength photons, while the bottom layer coated with silicon absorbs the long wavelength photons. To further increase the conversion efficiency, the research team has applied three innovative approaches, involving the use of low-temperature annealing, a tri-layer of molybdenum trioxide/gold/molybdenum trioxide, and a haze film.

The PolyU team believes that the cost of solar energy can drop significantly thanks to that concept, as compared to silicon cells available in the market. The PolyU research team will continue to work on further increasing the efficiency as well as the performance of large-scale fabrication of perovskite-silicon solar cells.

Researchers at MIT, the Skoltech Institute of Technology, and the University of Texas at Austin show that mobilizing oxygen atoms from the crystal surface of perovskite-oxide electrodes to participate in the formation of oxygen gas is key to speeding up water-splitting reactions. This work may carry great significance for the widespread adoption of water splitting to produce hydrogen fuel, a desirable way to move from traditional energy sources like fossil fuels towards clean, renewable energy sources.

In their study, perovskite oxide catalysts consisting of varying proportions of lanthanum and strontium with cobalt and oxygen were investigated. The scientists identified two key parameters controlling the catalytic performance of these materials: the covalency of the cobalt-oxygen bond and the number of oxygen vacancies. They then tuned their synthesis parameters to demonstrate that one particular material, strontium cobaltite (SrCoO2.7), exhibits highly active water electrolysis, much faster than the state-of-art catalyst iridium oxide, which contains precious metals. The team then managed to unravel how the reaction occurs on the atomic scale, illustrating an unprecedented new electrolysis pathway occurring on SrCoO2.7, and showed that it occurs as a result of the nature of the electronic structure in cobalt and oxygen. The researchers stated that this shortcut-like pathway with an exceptionally low energy barrier provides essential understanding not only for the development of highly-efficient catalysts, but also for future catalyst optimization.