Researchers at the Chinese Academy of Sciences (CAS), Peking University and  Soochow University have developed a polycrystalline silicon tunnelling recombination layer for perovskite/tunnel oxide passivating contact (TOPCon) silicon tandem solar cells (TSCs), which has reportedly achieved excellent efficiency and high stability.  

According to the team, previous efforts to increase device efficiency have mainly focused on improving the top sub-cell, leaving much room for improvement. The recombination layer, which serves as the electrical contact between the top and bottom sub-cells, plays a critical role in further efficiency progress. In this study, the researchers developed a polycrystalline silicon (poly-Si) tunnelling recombination layer that was incorporated into a perovskite/TOPCon silicon tandem cell. Through a two-step annealing strategy, the diffusion of boron and phosphorus dopants could be effectively restrained, granting the device excellent passivation and contact performance.

Researchers at Australia's University of Sydney, University of New South Wales, Macquarie University, Germany's Forschungszentrum Jülich, China's Southern University of Science and Technology ans Slovenia's University of Ljubljana have developed a perovskite-silicon solar cell design using a top perovskite PV device with an energy bandgap of 1.67 eV and a self-assembly monolayer based on carbazole. The tandem cell achieved a higher efficiency compared to counterparts without the monolayer and passed the IEC 61215 standard thermal cycling test.

The device is intended for applications as a top cell in perovskite-silicon tandem solar devices, where the upper cells must have a high energy bandgap to achieve output current matching. These top cells, however, suffer from a higher bandgap-voltage offset, due to non-radiative recombination and energetic misalignment between the perovskite and charge-selective layers. To address this issue, the team utilized a self-assembled monolayer (SAM) based on carbazole, which acts as an effective hole-selective layer (HSL). These SAMs were previously utilized in experimental solar cells and are commonly developed through a molecular glue added during processing in order to dramatically improve adhesion between the light-absorbing perovskite layer and the electron transport layer.

Researchers at China's Wuhan University assume that the practical use of all-perovskite tandem solar cells is hampered by the subpar performance and stability issues associated with mixed tin–lead (Sn–Pb) narrow-bandgap perovskite subcells. In their recent study, they focus on these narrow-bandgap subcells and develop an all-in-one doping strategy for them. 

The scientists introduce aspartate hydrochloride (AspCl) into both the bottom poly(3,4-ethylene dioxythiophene)–poly(styrene sulfonate) and bulk perovskite layers, followed by another AspCl posttreatment. They show that a single AspCl additive can effectively passivate defects, reduce Sn⁴⁺ impurities and shift the Fermi energy level. 

Reports suggest that LONGi Green Energy Technology managed to reach a conversion efficiency of 33.9% for its silicon-perovskite tandem solar cells.

The result, currently the highest efficiency record in the world for a perovskite/silicon tandem cell, has reportedly been confirmed by the US National Renewable Energy Laboratory (NREL).

Researchers at Empa, National University of Singapore (NUS) and Helmholtz Institute Erlangen-Nürnberg for Renewable Energy HI ERN have reported novel electrical and optical enhancement approaches to maximize the performance of perovskite front cells. 

The team introduced new electrical and optical techniques, using methyldiammonium diiodide and adjusting the optical interference spectrum. This resulted in a record efficiency of 20.2% (21.8% by J-V scan) for a semi-transparent perovskite cell and 81.5% average near-infrared transmittance. 

Cosmos Innovation, a company that relies on its AI platform called Mobius for "revolutionizing the approach to solar and semiconductor process development", has announced raising $19.7 million in total funding. The funding will support the company's different approach to developing perovskite silicon tandem solar cell technology.

The funding coincides with Cosmos Innovation's unveiling of Mobius, its pioneering AI recipe optimization platform. Mobius has reportedly been demonstrated across various sectors, including solar, silicon carbide, advanced data center chips and advanced packaging. This platform fuels Cosmos Innovation's ambitious endeavor: construction of the world's first self-learning fab in the solar and semiconductor space.

Researchers at the University of North Carolina at Chapel Hill and Arizona State University and have designed a large-area perovskite-silicon tandem solar cell that achieved a steady-state power conversion efficiency of 25.1% for tandem devices with a large aperture area of 24 cm².

The team set out to overcome shunting, which is a common issue when scaling up perovskite solar technologies from small-area cells to large-area devices. “Shunts” in PV cells create alternate pathways for a solar-generated charge, leading to power losses. Reduced shunt resistance is associated with multiple forms of module degradation and failure, including hotspots and potential-induced degradation.

A group of scientists from Germany's Fraunhofer Institute for Solar Energy Systems (Fraunhofer ISE), with support from Oxford PV Germany, have examined shingling as an interconnection method for perovskite-silicon tandem (PVST) cells.

Full-format perovskite-silicon tandem shingle modules produced at Fraunhofer ISE in collaboration with Oxford PV. Image from Solar Energy Materials and Solar Cells.

The scientists explained that the combination of PVST cells with shingling allows boosting the module efficiency even further due to the increase of the photoactive area through the absence of cell gaps. They went on to say that shingling suits the temperature limitations of the PVST cells since the main factor for the choice of the processing temperature is the curing conditions of the electrically conductive adhesive.

Oxford PV has announced that its perovskite-on-silicon tandem solar cells will be deployed for the first time on the race car of the Top Dutch Solar Racing team for the upcoming Bridgestone World Solar Challenge. 

Taking place between the 22nd and 29th of October 2023, the competition brings some of the world’s greatest scientific and engineering talent to Australia to travel 3,000 kilometers in a vehicle powered only by the energy of the sun. University-affiliated teams push the limits of technological innovation and travel the outback in solar-powered vehicles that they have designed, engineered and ultimately built themselves.

Researchers from Southeast University and the University of Liberal Arts Bangladesh have designed and simulated an all-inorganic lead-free tandem photovoltaic cell based on copper, indium, gallium and selenium (CIGS) thin-film technology and perovskite.

The proposed top cell (a) and bottom cell (b), image from Heliyon

The novel device architecture is said to have the potential to reach a power conversion efficiency of 38.39%. “The main objective of this work is to find an efficient combination of non-toxic solar cells with high efficiency so that it saves time and effort before going for fabrication,” the scientists said in their work, noting that the perovskite and materials used for the cell are lead-free.