Tandem

Recently, a University of Louisville team of researchers used nanoparticle inks by Sofab Inks (a U of Louisville spinout) to create PSCs with ~20% PCE on flexible substrates. Their study addresses the solvent scope and perovskite compatibility of acetate-stabilized yttrium-doped SnO₂ (Y:SnO₂) dispersions.

Tin oxide (SnO₂) stands out as a compelling electron transport material (ETM) for perovskite solar cells (PSCs), boasting exceptional optoelectronic properties, coupled with low-temperature solution processability, cost-effectiveness, and remarkable stability. However, the widespread application of SnO₂ has been hindered by solvent incompatibilities, limiting its use to devices where it is deposited beneath the perovskite layer. To unlock the full potential of SnO₂ and expand its use across various device structures, including inverted PSCs and tandem devices, innovative deposition strategies will need to be developed. These advancements could pave the way for more efficient and versatile solar cell designs, pushing the field of photovoltaics forward.

The scientists showed that dispersions in several lower alcohols and select polar aprotic solvents can be directly deposited on perovskite using scalable and low-temperature processes. In addition, they are compatible with various perovskite formulations, including those with mixed cations and mixed anions.

It was reported that China-based Risen Energy, a company primarily focused on grid-connected PV power generation systems, announced its new achievement in the research and development of perovskite and HJT tandem solar cells. A power conversion efficiency of 30.99% was reportedly achieved by Risen Energy’s R&D institution, and the result was confirmed by the China National Center of Supervision and Inspection on Solar Photovoltaic Products Quality (CPVT).

As a leading solar module manufacturer in China, Risen Energy believes that HJT solar cells with unique structure and features are promising products among p-type and n-type single junction solar cells. HJT’s advantages are significant in perovskite and silicon tandem solar cells, making it naturally suitable as a base for tandem cells. HJT is seen as one of the best bottom cells for crystalline silicon and perovskite tandem cells. Other types of crystalline silicon cells, due to the lack of ITO film, require redesign of the structure prior to tandem processing, which increases cost and complexity.

India-based P3C has announced a partnership with the National Institute of Solar Energy (NISE). 

P3C and NISE have signed a Memorandum of Understanding (MoU) to accelerate India’s transition to a low-carbon, sustainable future. This partnership will focus on advancing perovskite solar technology and powering next-generation solar solutions, including glass and flexible perovskite modules, tandem solar cells, and advanced PV innovations for both urban and rural environments. The two parties' shared goal is to make clean energy accessible, efficient, and scalable across India, from rooftops and farmlands to smart cities and remote villages.

Researchers from China's Westlake University, Advanced Solar Technology Institute of Xuancheng and Turkey's Marmara University have addressed the stability issues of perovskite solar cells (PSCs) by developing a divalent cation replacement strategy that mitigates ionic migration while limiting phase segregation. 

Using the new method, the scientists fabricated a champion cell that showed a PCE of 23.20% (certified 22.71%) for a single-junction PSC with a bandgap between 1.67 eV and 1.68 eV. Furthermore, a PCE of 30.13% was obtained for mechanically stacked perovskite/Cu(In,Ga)Se₂ tandem devices, and a PCE of 21.88% for transparent perovskite devices. Finally, they obtained a steady-state PCE of 23.28% (certified 22.79%) for flexible monolithic perovskite/Cu(In,Ga)Se₂ tandem cells.

ART-PV India, an IIT Bombay-incubated start-up, has been awarded a $10 million grant by the Ministry of New and Renewable Energy (MNRE). The funding will enable the company to set up a manufacturing plant for high-efficiency tandem solar cells.

ART-PV has developed a 4T cell with PCE >30% on small area ~1 cm², which will be transferred to 2T using industry partners supplying semi-processed bottom sub-cells.

Scientists from HZB and Humboldt University Berlin have reported a CIGS-perovskite tandem cell that sets a record with an efficiency of 24.6%, certified by the independent Fraunhofer Institute for Solar Energy Systems.

The team's new tandem solar cell combines a bottom cell made of CIGS with a top cell based on perovskite. By improving the contact layers between the top and bottom cells, they were able to increase the efficiency to 24.6%. This cell was the result of a successful team effort: the top cell was fabricated by TU Berlin master's student Thede Mehlhop under the supervision of Stefan Gall. The perovskite absorber layer was produced in the joint laboratory of HZB and Humboldt University of Berlin. The CIGS sub-cell and contact layers were fabricated by HZB researcher Guillermo Farias Basulto. He also used the high-performance cluster system KOALA, which enables the deposition of perovskites and contact layers in vacuum at HZB.

Researchers from China's Northwest Normal University, Xidian University and Xi'an Shiyou University have developed a four-terminal perovskite-CIGS tandem solar cell based on a top semi-transparent perovskite device with an efficiency of 21.26% and a high bifaciality factor of 92.2%. The scientists used a solvent-annealing strategy to produce a perovskite film with full coverage, larger grains, superior crystallinity and free of detectable lead iodide impurity.

The team fabricated a four-terminal (4T) tandem solar cell based on a top semi-transparent perovskite device and a bottom cell relying on copper-indium-gallium-selenide (CIGS). The scientists used a stepwise dimethyl sulfoxide (DMSO) solvent-annealing method to improve the crystallinity of the perovskite film used in the perovskite top cell and fabricated films with a wide bandgap of 1.68 eV via two consecutive heating steps: annealing at 100 C and then 80 C.

A TU Delft team of researchers has examined how perovskite materials could be optimized in order to achieve improved performance in bifacial two-terminal perovskite-silicon tandem solar cell technologies. They targeted bifacial two-terminal tandem PV optimization by considering aspects not included in previous studies, such as the effect rear irradiance has on the optimal bandgap energy and thickness of the perovskite cell in this kind of a tandem module.

The bifacial perovskite/silicon cell structure used in the simulations. Image from: Solar Energy Materials and Solar Cells

The team's findings show that bifacial tandems have over a 25% gain in energy yield compared to bifacial single junction modules and up to 5% gain compared to monofacial tandem modules.

As part of CEA and 3SUN's joint development of tandem perovskite-over-silicon solar cell technology, a new milestone was announced, setting a new efficiency record of 30.8%. This cell was developed in CEA’s laboratories, located on the campus of the National Institute for Solar Energy (INES).

The tandem architecture used by the CEA and 3SUN for this record makes exceeding the theoretical efficiency limit - set at around 29% for conventional silicon technologies currently being produced in photovoltaic gigafactories - possible. Furthermore, while most international records are achieved on a 1 cm² area, CEA and 3SUN achieved this performance on a 9 cm² cell, which should facilitate the transition to industrial scale.

EneCoat Technologies has announced a conversion efficiency of over 30% with a 4-terminal tandem cell consisting of stacked perovskite and crystalline silicon solar cells in a joint development project with Toyota Motor Corporation. 

This achievement underscores the profound research and development capabilities of both companies in the field of perovskite solar cells and accelerates the practical application of high-efficiency solar cells, which is the objective of the joint development project. In this project, the two companies focused on the transmittance of perovskite solar cells and succeeded in improving the infrared transmittance to 81%.