January 2019

Researchers at Solliance, in collaboration with MiaSole Hi-Tech Corp., have designed a flexible solar cell with an impressive power conversion efficiency of 21.5%. The solar cell combines two thin-film solar cell technologies into a 4 terminal tandem solar cell stack: a top flexible semi-transparent perovskite solar cell with a bottom flexible copper indium gallium selenide (CIGS) cell.

A tandem solar cell, which combines a perovskite and a Cu(In,Ga)Se2 (CIGS) cell, has the potential for high conversion efficiency exceeding single junction solar cell performance thanks to tunable and complementary bandgaps of these individual thin film solar cells. CIGS technology has a proven track record as a high efficiency and stable solar technology, and has entered high volume manufacturing in multi-GW scale around the world. CIGS technology has been successfully used to produce high efficiency flexible and lightweight cells and modules, which address markets where heavy and rigid panels cannot be used. Perovskite solar cells, promise low cost solar technology based on abundant materials. Combining both technologies in a flexible and lightweight package expands the horizon of high performance, flexible, and customizable solar technology.

Researchers from the University of Potsdam, Humboldt University, Helmholtz-Zentrum Berlin and Technical University Berlin have recently published a paper on perovskite solar cell improvement with the addition of Strontium.

(a) cell structure in the study (b) perovskite structure used here, indicating how Sr can replace Pb

The team managed to reach record Voc for pin-type perovskite solar cells and elucidated the effect of the Strontium incorporation.

Researchers at Tokai University report a systematic study on the effects that using different forms of titanium oxide in planar perovskite solar cells has on the performance of the devices.

The team from Tokai university focused on the electron-transport layer. The material of choice for this component is often titanium oxide, whose electronic structure makes it easy to collect electrons from the perovskite layer. Titanium oxide has several crystal polymorphs including anatase, brookite, and rutile. They have different structures and properties and their distinct morphologies influence the quality of the perovskite layer, so the choice of polymorph influences the overall performance of the solar cell. This is why understanding this influence is important for optimizing the efficiency of devices.

Researchers at the Okinawa Institute of Science and Technology Graduate University (OIST) have reportedly resolved a fundamental weakness in perovskite solar cells (PSCs). Their innovations appear to improve both the devices' stability and scalability and could be key to commercializing PSCs.

The study supports prior evidence that a commonly used material in PSCs, called titanium dioxide, degrades the devices and limits their lifetime. The researchers replaced this material with tin dioxide, a stronger conductor without these degrading properties. They optimized their method of applying tin dioxide to produce stable, efficient and scalable PSCs. "We need solar modules that can last for at least 5 to 10 years. For now, the lifetime of PSCs is much shorter," said Dr. Longbin Qiu, first author of the paper and a postdoctoral scholar in the OIST Energy Materials and Surface Sciences Unit, led by Prof. Yabing Qi.

A team of researchers from UNIST in South Korea has identified a tin-based perovskite which could open new possibilities for the application of lead-free perovskites in solar cells. The cesium-tin based double perovskite material, Cs₂SnI₆, had previously been identified as promising for use in solar cells, however little research into the perovskite's surface properties had been carried out.

The team created a three-electrode system allowing them to confirm that charge transfer occurred through the surface state of the material; and used this knowledge to engineer a Cs₂SnI₆ based organic dye sensitized solar cell.

German and Greek scientists are working with industrial partners on the technological feasibility of making solar modules based on perovskite absorbers. The prototypes should be freely configurable in size, shape and color. The research project Printed Perovskite Modules for Building Integrated Photovoltaics ' 'Printpero' ' is aimed at developing highly efficient and cost-effective solar modules.

The panels proposed would incorporate perovskite-based thin-film solar cells which achieve efficiencies of more than 23% in the laboratory, said the coordinator of the German-Greek research project, Germany's Karlsruhe Institute of Technology (KIT).

Researchers from the Ulsan National Institute of Science and Technology (UNIST) have developed perovskite LEDs (PeLED) which are flexible enough to be folded. A transparent material was used in the electrode of the device as a replacement for metal to ensure translucency.

Flexible translucent PeLED maintains performance even when bending curvature is small

According to the team, PeLED is a kind of light emitting diode (LED) that emits light by injecting current into a compound. This device uses a perovskite material as an active layer that emits light by receiving electricity, and its advantages include high electron mobility, good color purity, and easy color control. However, conventional PeLEDs are low in flexibility and opaque due to limitations of metal electrodes.

An international team of researchers, led by Aram Amassian at North Carolina State University, has demonstrated the construction of field-effect transistors using a single crystal, hybrid perovskite semiconductor.

While the design of perovskite solar cells has matured to the point of near-commercialization, making hybrid perovskites function as field-effect transistors has been more of a challenge. This is in part due to the fact that perovskite films typically consist of multiple crystals with random orientations that include grain boundaries and various kinds of defects in their atomic crystal lattices. These often limit how well charge carriers (electrons or 'holes') can move through them.

A research team led by San Diego State University chemists Xiaolin Zhu and Yong Yan has shown that perovskite materials methylammonium lead tribromide and the cesium analog are not only two of the most studied solar-cell perovskites, but can also function as highly active photocatalysts for organic synthesis.

The researchers used standard methods to prepare the low-cost nanocrystal catalysts and explored their reactivity under blue-light illumination in tests with 2-bromoacetophenone and octanal. The reactions generated a mixture of products, including the aldehyde α-alkylation product, other C-coupling products, and dehalogenated acetophenone.

Researchers from the University of Utah have developed two spintronics devices based on perovskite materials. The researchers used these new devices to demonstrate the high potential of perovksites for spintronics systems. This is a followup to the exciting results announced in 2017 by the same group that showed advantages of perovskites for spintronics.

The researchers used an organic-inorganic hybrid perovskite material with a heavy lead atom that features strong spin-orbit coupling and a long injected spin lifetime. The first device was a spintronic LED, which worked with a magnetic electrode instead of an electron-hole electrode. The perovskite LED lights up with circularly polarized electroluminescence.