Efficiency - Page 51

Researchers at the Energy Research Center of the Netherlands (ECN) have developed a bifacial tandem solar cell with a conversion efficiency of 30.2%. The new cell device ' created with Dutch consortium Solliance ' was made by applying a newly developed perovskite cell on top of an industrial bifacial crystalline silicon version.

This approach, according to the scientists, enables a significantly higher power conversion efficiency as one cell is optimized for high energy photons, and the other low energy particles. 'The tandem device proposed here uses a four-terminal configuration, thus having separate circuits for the top and bottom cells that allow for dynamic fine tuning and optimization of the energy yield,' the creators of the cell wrote. The cell is also said to be better able to capture light on its front and rear sides by responding to the variability of incident light through its electronic design.

Researchers at the Japanese Kanazawa University aim to improve the performance of perovskite solar cells by using two kinds of titanium oxide - anatase and brookite.

The team claims to have reached a conversion efficiency of 16.82% in a perovskite cell by applying a brookite layer made of water-solute brookite nanoparticles on an anatase layer. This reportedly helps to improve the transport of electrons from the center of the cell to its electrodes, while also preventing charges from recombining at the border between the perovskite material and the electron transport layer. 'Together, both these effects allow us to achieve higher solar cell efficiencies,' said the research coordinator, Md. Shahiduzzaman.

The following post is a sponsored post by MBRAUN

Prof. Dr. Steve Albrecht and his 11-member team of the Helmholtz Innovation Lab HySPRINT at
Helmholtz-Zentrum Berlin (HZB) develop tandem solar cells that combine the advantages of silicon and perovskite solar cells. In order to create the best research conditions, Prof. Albrecht had installed systems from the market leaders, MBRAUN and CreaPhys (a part of MBRAUN).

HySPRINT Perovskite Lab © HZB / M. Setzpfandt

The Perovskite cluster is composed of 4 different parts: Precursor synthesis, wet coating with spin coater, evaporation of perovskites and metallization, scaling with inkjet printer and slot die coater under laminar flow. Every part of the cluster is integrated in inert gloveboxes under inert atmosphere to guarantee the best performance of the devices, as well as the best repeatability of the processes.

Researchers from HZB, Oxford University, Technical University Berlin and Oxford PV have shown that the infrared reflection losses in tandem cells processed on a flat silicon substrate (such as perovskite/silicon tandem cells) can be significantly reduced by using an optical interlayer, consisting of nanocrystalline silicon oxide. Based on this, the team managed to achieve impressive efficiency and reported that the best tandem device in this work reached a certified conversion efficiency of 25.2%.

a) Cross-section of the simulated monolithic perovskite/SHJ tandem cell (layer thicknesses and morphological features not to scale). b) Cross-sectional SEM image of the top region of the tandem device.

Perovskite/silicon tandem solar cells are attractive for their potential for boosting cell efficiency beyond the crystalline silicon (Si) single-junction limit. However, the relatively large optical refractive index of Si, in comparison to that of transparent conducting oxides and perovskite absorber layers, often results in significant reflection losses at the internal junction between the cells in monolithic (two-terminal) devices. Therefore, light management is crucial for improving photocurrent absorption in the Si bottom cell.

A team of researchers from UC San Diego, Georgia Institute of Technology, Purdue University, MIT and Argonne National Laboratory has reported new findings on perovskites, that could pave the way to developing low-cost, high-efficiency solar cells. Using high-intensity X-ray mapping, they explain why adding small amounts of cesium and rubidium salt improves the performance of lead-halide perovskites.

'Perovskites could really change the game in solar. They have the potential to reduce costs without giving up performance. But there's still a lot to learn fundamentally about these materials,' said David Fenning, a professor of nanoengineering at the University of California San Diego and co-senior author of the study. 'We're looking deeper into some of the state-of-the-art chemistries to understand what drives perovskite performance and why they work so well.'

Researchers at the Germany-based Helmholtz Center Berlin (HZB) have announced a thin-film solar cell made of perovskite and copper-indium-gallium-selenide (CIGS) with an efficiency of 21.6%.

The HZB researchers said they used a simple, robust production process suitable for scaling up. Rutger Schlatmann, director of the HZB's Institute PVcomB, spoke of an 'enormous step in the direction of commercial production'. The HZB team's tandem cell could theoretically reach an efficiency of more than 30%, according to the researchers.

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.