Tandem - Page 20

Researchers led by Eindhoven University of Technology in the Netherlands have developed a process that allowed them to fabricate three perovskite layers, and combined these layers into a device that reached 16.8% conversion efficiency.

While tandem cells are the focus of intensive research, combining several active layers into one cell is less explored. Efficiencies close to the 40% mark have been achieved with III-V materials, but for all perovskite devices, the efficiency record previously stood at 6.7%.

A team of researchers, led by China's Nanjing University, have found that a chemical most commonly used in the textile industry can also serve as a performance-enhancing additive for mixed lead/tin perovskite thin films. They have used this additive to create a two perovskite tandem cell measuring 1.05cm² that achieved 24.2% efficiency.

Mixed lead-tin perovskites are known to have the right narrow bandgap for use as the top cell in a tandem device. However, despite similar theoretical efficiency potential, the development of these materials has stayed behind that of pure lead perovskites. One reason for this, according to scientists, is that the tin tends to oxidize during fabrication of the film, leading to high levels of defects and non-uniformity in the film. 'Defective grain surfaces are vulnerable to trap generation and Sn²⁺ oxidation,' state the group led by Nanjing University Professor Hairen Tan. 'And this works against the stability, efficiency, and scaling of mixed Pb'Sn perovskite solar cells and all-perovskite tandems.'

Scientists at the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL) have developed a new wide-bandgap perovskite layer – called Apex Flex – which they claim is able to withstand heat, light, and operational tests, and at the same time provide a reliable and high voltage.

With this material, they have built tandem solar cells with 23.1% power conversion efficiency on a rigid substrate, and 21.3% on flexible plastic. The new Apex Flex wide-bandgap perovskite recombination layer is grown with atomic layer deposition (ALD). The new material is described as a “nucleation layer consisting of an ultra-thin polymer with nucleophilic hydroxyl and amine functional groups for nucleating a conformal, low-conductivity aluminum zinc oxide layer.”

Researchers from King Abdullah University of Science and Technology (KAUST) have fabricated efficient, two-terminal monolithic perovskite-silicon tandem solar cells and tested them outdoors. The tandem device that resulted from this research was found to be more stable than conventional perovskite cells and, importantly, optimized for use in industry.

Perovskite/silicon cells under test at KAUST outdoor facility

The findings of KAUST Research Scientists Dr. Erkan Aydin and Dr. Thomas Allen, and colleagues in Professor Stefaan De Wolf's group, indicate that the temperature dependence of both the silicon and perovskite bandgaps'which follow opposing trends'shift the current-matching-optimization point away from that for two-terminal tandems under standard test conditions.

Researchers at Cornell University and University of Cambridge have analyzed the overall environmental impact of two types of solar panels, comparing these against panels made with crystalline silicon wafers ' the current industry standard.

The team found that a solar panel made from two layers of perovskite requires a smaller total energy input and results in fewer carbon emissions. The panel, a perovskite-perovskite tandem, contains two layers of the material on top of each other, each optimized to absorb a section of the electromagnetic spectrum.

Researchers at the University of Sydney and University of New South Wales working with chemists at the University of Wisconsin-Madison in the United States have created a highly efficient and long-lasting solar-flow battery, which is a way to generate, store, and redeliver renewable electricity from the sun in one device.

The new device is made of perovskite-silicon tandem solar cells integrated with specially designed chemical battery components. The solar-flow battery achieved a new record efficiency of 20 percent conversion of energy from the sun. This is 40 percent more efficient than the previous record for solar-flow batteries, which were also developed in the University of Wisconsin Jin lab where lead author, PhD student Wenjie Li, is based.

Researchers at Arizona State University have demonstrated a perovskite-silicon tandem cell they claim has low reflectance losses and strong potential for commercial production. The ASU team says that this new cell could lead to 30% efficiency tandem devices. The tandem architecture involves a manufacturing process featuring the solution-based blading of perovskites onto textured silicon wafers.

Image credit: Joule

The device is manufactured in a nitrogen-assisted blading process which ensures deposition of the perovskite layer onto textured silicon is achieved with typical pyramid heights of 1μm. The manufacture of such tandem devices typically results in perovskite heights of 3-10μm.

Researchers from Helmhotlz-Zentrum Berlin (HZB), collaborating with teams from University of Cambridge, Eindhoven University of Technology, Nicolaus Copernicus University, Salerno University and others, have developed a monolithic "two-terminal" tandem cell made of CIGS and perovskite that achieved a certified efficiency of 24.16%, with a thickness of well below 5 micrometers - which would allow the production of flexible solar modules.

Tandem cells combine two different semiconductors that convert different parts of the light spectrum into electrical energy. Metal-halide perovskite compounds mainly use the visible parts of the spectrum, while CIGS semiconductors convert rather the infrared light. CIGS cells, which consist of copper, indium, gallium and selenium, can be deposited as thin-films with a total thickness of only 3 to 4 micrometers; the perovskite layers are even much thinner at 0.5 micrometers.

This article is an extract from The Perovskite Handbook, 2020 edition, and explains the current market status of Perovskites Solar Panels.

Solar Panels is the most prominent potential perovskite application, as synthetic perovskites are recognized as inexpensive base materials for high-efficiency commercial photovoltaics. Perovskite PVs are constantly undergoing research and improvement, going from just 2% in 2006 to over 23% today, and constantly improving. Experts forecast that the market for perovskite PV will reach $214 million in 2025.

Power efficiency is obviously a key metric for solar power technologies. In this article we'll explain how solar system efficiency is defined and the current power efficiency market status of PSCs.

The US National Science Foundation (NSF) awarded nTact with $708,000 project to develop a reliable, reproducible, and cost-effective upscaling of perovskite photovoltaic devices using an industry-proven slot-die coating technique. This process will ultimately be used to produce flexible and rigid, highly efficient perovskite solar cells.

This is the second stage of this Small Business Technology Transfer Project (STTR-II) that has three objectives: