Tandem

Scientists from Kaunas University of Technology and Vilnius University in Lithuania and University of Colorado in the U.S have proposed a method for increasing the stability and performance of perovskite solar cells. The team synthesized a new class of carbazole-based cross-linkable materials, which are resistant to various environmental effects, including strong solvents used in the production of solar cells.

When applied as hole transporting layers, the new materials helped achieve the 16.9% efficiency of the inverted-architecture perovskite cells at the first attempt. It is expected to reach higher efficiency upon optimization.

Researchers from the Karlsruhe Institute of Technology (KIT) and the Forschungszentrum Jülich GmbH in Germany have developed a monolithic perovskite-silicon solar cell with a power conversion efficiency of 20%, using a novel lamination approach.

The team investigated how this lamination process can be applied to perovskite/silicon tandem technology. They explained that the solar cells are the first prototypes and that lamination is a suitable alternative fabrication method for monolithic perovskite/silicon tandem solar cells. The lamination approach, they said, is particularly interesting for perovskite-based PV, as it notably increases the degree of freedom in the choice of materials and accessible deposition techniques.

Researchers from Switzerland's Federal Laboratories for Materials Science and Technology (EMPA) and École Polytechnique Fédérale de Lausanne (EPFL) have designed a four-terminal tandem mini-module based on perovskite and copper, indium, gallium and selenium (CIGS) with an aperture area of around 2 cm², and a geometric fill factor of over 93%.

Processing sequence of flexible NIR-transparent perovskite mini-module. Image from RRL Solar

The team reports that the key to efficient flexible perovskite-CIGS tandem modules is the development of near-infrared (NIR) transparent perovskite solar modules on a flexible polymer foil. To achieve these results, the researchers had to overcome the challenges of laser patterning on flexible substrates to realize the first all-laser scribed monolithically interconnected NIR-transparent perovskite mini-modules on polymer film. The perovskite mini-module used in the tandem panel was fabricated on a flexible polyethylene napthalathe (PEN) substrate mounted to a glass substrate in a p–i–n device architecture. This configuration, according to the research team, shows reduced absorption in the NIR region.

Researchers from Ulsan National Institute of Science and Technology (UNIST) in South Korea and the University of Pittsburgh in the U.S have reported a power conversion efficiency of 23.5% in a perovskite-silicon tandem solar cell by applying a special textured anti-reflective coating (ARC) polymeric film.

The team prepared the multifunctional film with phosphor particles measuring 10 μm in diameter. They are able to block ultraviolet (UV) light and silicon dioxide (SiO₂) nanoparticles with a diameter of 10 nm to increase the ability of a perovskite-silicon tandem solar cell to absorb visible light. The scientists explained that the phosphors increase the reflectance of the ARC film, due to their large particle size, thus causing a backward light scattering issue. This in turn is compensated by the addition of the spherical SiO₂ nanoparticles.

Scientists from the University of Tokyo have reported a 26.2% power conversion efficiency for a four-terminal tandem solar cell based on perovskite and copper, indium, gallium and selenium (CIGS). The researchers said these results are a world record for such tandem solar devices and attributed the improvements to the performance of the perovskite top cell.

They built the 1-square-centimeter perovskite device using a transparent conductive material made of indium tin oxide (ITO), which was deposited via sputtering and without thermally evaporated Molybdenum oxides ( MoOx). “By eliminating the use of the MoOx buffer layer, we were able to develop semi-transparent PVK cells with higher durability and transmittance,” the scientists said.

A team of scientists from Technische Universität Berlin, Oxford PV Germany, German Philipps-Universität Marburg, Helmholtz Zentrum Berlin (HZB) and Oxford PV UK has, for the first time, assessed the environmental performance of industrially produced perovskite-on-silicon PV modules. Understanding the environmental impact of solar PV modules across their entire lifecycle is essential for the design of more sustainable solar energy systems. However, lifecycle assessment of perovskite-on-silicon PV modules has so far relied heavily on data from laboratory and test facilities rather than manufacturers.

The researchers conducted a comprehensive lifecycle assessment of a perovskite-on-silicon module across a number of categories including global warming potential, water consumption, human and marine toxicity, and metals usage. They assessed the materials and energy input for a module’s ‘cradle to gate’ lifecycle, covering all materials and energy input for wafer production, manufacture of the perovskite cell, and module production. The researchers then weighed up the environmental impact of the tandem module against the electricity generated over its lifetime.

Researchers from the Swiss Center for Electronics and Microtechnology (CSEM) and the École polytechnique fédérale de Lausanne (EPFL) have reported a power conversion efficiency exceeding 30% for a 1 cm² tandem perovskite-silicon solar cell, which represents a world record for a PV device of this kind. The team achieved an efficiency of 30.93% for a 1 cm² solar cell based on high-quality perovskite layers from solution on a planarized silicon surface and an efficiency of 31.25% on a cell of the same size and fabricated with a hybrid vapor/solution processing technique compatible with a textured silicon surface.

“These results constitute two new world records: one for the planar and one for the textured device architecture,” the researchers explained, noting that both efficiencies were certified by the US Department of Energy's National Renewable Energy Laboratory (NREL). “The latter approach provides a higher current and is compatible with the structure of current industrial silicon solar cells”. Unfortunately, the researchers did not disclose technical details on how they improved the efficiency of both devices.

A research group that includes scientists from Chinese module manufacturer JinkoSolar, Australian National University, the Beijing Institute of Technology and Peking University has developed a monolithic perovskite-silicon n-type tandem solar cell based on tunnel oxide passivated contacts (TOPCon) tech for the bottom cell.

“We fabricate the perovskite sub-cell conformally on the damage-etched front surface to mitigate the negative impacts of rough c-Si substrates, thus preventing shunt paths across carrier transport layers, absorber layers, and their interfaces in relevance,” the scientists said, noting that they followed a standard wafering and etching process that is commonly used in the PV industry.

Korea-based Hanwha Solutions has announced that it has come one step closer to mass-producing perovskite solar cells. Hanwha Q CELLS, the solar power business division of Hanwha Solutions, recently succeeded in developing a 6-inch solar tandem cell. 

Hanwha Solutions has reportedly overcome the disadvantages of small area cells, which were a constraint on mass production of perovskite batteries, paving the way for mass production of next-generation solar cells. The company is currently working on performance improvement of the solar tandem cell, with the goal of beginning mass production of perovskite batteries in 2025. Hanwha Q CELLS said it is preparing for mass production of the tandem cells.

Researchers from Wuhan University and Shenzhen University in China have designed a four-junction tandem (4T) solar cell based on perovskite and copper, indium, gallium and selenium (CIGS), through a novel surface passivation technique that uses guanidine bromide (GABr).

The team tested GABr in mixed solvents combining isopropyl alcohol (IPA) and toluene (TL), which they said can efficiently passivate interface and grain boundary defects by minimizing the IPA solubility of the perovskite surface. They compared the mixing of IPA with ethyl acetate (EA), chlorobenzene (CB), and toluene (TL) to dissolve GABr, and further optimized the concentration of GABr and the mixing ratio of the two solvents.